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Fundamental understanding of the dependence between the structure and composition on the electrochemical CO2 reduction reaction (CO2 RR) would guide the rational design of highly efficient and selective electrocatalysts. A major impediment to the deep reduction CO2 to multi-carbon products is the complexity of carbon-carbon bond coupling. The chemically well-defined catalysts with atomically dispersed dual-metal sites are required for these C-C coupling involved processes. Here, we developed a catalyst (BIF-102NSs) that features Cl- bridged dimer copper (Cu2 ) units, which delivers high catalytic activity and selectivity for C2 H4 . Mechanistic investigation verifies that neighboring Cu monomers not only perform as regulator for varying the reaction barrier, but also afford distinct reaction paths compared with isolated monomers, resulting in greatly improved electroreduction performance for CO2 .

Developing electrocatalytic energy conversion technologies for replacing the traditional energy source is highly expected to resolve the fossil fuel exhaustion and related environmental problems. Exploring stable and high-efficiency electrocatalysts is of vital importance for the promotion of these technologies. Single-atom catalysts (SACs), with atomically distributed active sites on supports, perform as emerging materials in catalysis and present promising prospects for a wide range of applications. The rationally designed near-range coordination environment, long-range electronic interaction and microenvironment of the coordination sphere cast huge influence on the reaction mechanism and related catalytic performance of SACs. In the current Review, some recent developments of atomically dispersed reactive centers for electrocatalytic CO2 reduction and water splitting are well summarized. The catalytic mechanism and the underlying structure-activity relationship are elaborated based on the recent progresses of various operando investigations. Finally, by highlighting the challenges and prospects for the development of single-atom catalysis, we hope to shed some light on the future research of SACs for the electrocatalytic energy conversion. Ministry of Education (MOE) National Research Foundation (NRF) Published version X.W.L. acknowledges the funding support from the Ministry of Education of Singapore through the Academic Research Fund (AcRF) Tier-2 grant (MOE2017-T2-2-003) and Tier1 grant (RG116/18), and the National Research Foundation (NRF) of Singapore via the NRF Investigatorship (NRFNRFI2016-04).

Isolated cobalt atoms have been successfully decorated onto the surface of W18O49 ultrathin nanowires. The Co-atom-decorated W18O49 nanowires (W18O49@Co) greatly accelerate the charge carrier separ...

A pair of homochiral metal–organic frameworks are elaborated by employing flexible enantiopure ligands. They possess interesting double helical chains and rich hydrogen-bonding environment, exhibiting excellent chiral recognition ability to carvone.

Single-atom catalysts (SACs), in which the metal active sites are isolated on the support and stabilized by coordinated atoms such as oxygen, nitrogen, sulfur, etc., represent the maximum usage efficiency of the metal atoms. Benefiting from the recent progress in synthetic strategies, characterization methods, and computational models, many SACs that deliver an impressive catalytic performance for a variety of reactions have been developed. The catalytic selectivity and activity are critical issues that need to be optimized and augmented in the areas of nanotechnology and biomedicine. This review summarizes some recent experimental and theoretical progress aimed at clarifying the structure of SACs and how they influence the catalytic performance. The examples described here elaborate on the utility of SACs and highlight the strengths of these catalysts in the applications of biomedicine, environmental protection, and energy conversion. Finally, some current challenges and future perspectives for SACs are also discussed., Some recent experimental and theoretical progress is summarized, aimed at clarifying the structure of single-atom catalysts and how they influence the catalytic performance.

At the molecular level, metal coordinates are crucial for stabilizing an appropriate electronic configuration for high-efficiency oxygen reduction reaction (ORR) electrocatalysts. In this work, an excellent platform to realize the decoration of Fe coordinates at the subnanometer scale into nitrogen-doped carbon networks (designated as Fe–Fe@NC) is provided. X-ray absorption spectroscopy confirmed the precise configuration of Fe coordinates with Fe–Fe and Fe–N coordinations at the molecular level. As a cathode catalyst, the newly developed Fe–Fe@NC exhibited superior ORR performance and a higher peak power density of 175 mW cm−2 in Zn–air batteries. Unlike most reported pristine Fe-based catalysts, Fe–Fe@NC also showed good oxygen evolution reaction (OER) activity, with a low operating potential (1.67 V vs. RHE) at a current density of 10 mA cm−2. Calculations based on density functional theory revealed that the Fe–Fe coordination in Fe subclusters favored the 4e− transfer pathway and, thus, achieved highly active catalytic performance. This work reveals that iron clusters at the subnanometer scale provide an optimized electronic structure for enhanced ORR activity.

Conductive metal-organic framework (MOF) materials have been recently considered as effective electrocatalysts. However, they usually suffer from two major drawbacks, poor electrochemical stability and low electrocatalytic activity in bulk form. Here, we have developed a rational strategy to fabricate a promising electrocatalyst composed of a nanoscale conductive copper-based MOF (Cu-MOF) layer fully supported over synergetic iron hydr(oxy)oxide [Fe(OH)x] nanoboxes. Owing to the highly exposed active centers, enhanced charge transfer, and robust hollow nanostructure, the obtained Fe(OH)x@Cu-MOF nanoboxes exhibit superior activity and stability for the electrocatalytic hydrogen evolution reaction (HER). Specifically, it needs an overpotential of 112 mV to reach a current density of 10 mA cm−2 with a small Tafel slope of 76 mV dec−1. X-ray absorption fine structure spectroscopy combined with density functional theory calculations unravels that the highly exposed coordinatively unsaturated Cu1-O2 centers could effectively accelerate the formation of key *H intermediates toward fast HER kinetics. Ministry of Education (MOE) National Research Foundation (NRF) Published version X.W.L. acknowledges the funding support from the Ministry of Education of Singapore through the Academic Research Fund (AcRF) Tier-2 funding (MOE2019-T2-2-049) and the National Research Foundation (NRF) of Singapore via the NRF Investigatorship (NRF-NRFI2016-04).

Achieving a molecular level understanding of surface performance of nanomaterials by modulating the electronic structure is important but challenging. Here, we have developed a hollow microcube framework constructed by Mo-defect-rich ultrathin MoS2 nanosheets (HMF-MoS2) through a zeolite-like-framework-engaged strategy. The hollow structured HMF-MoS2 delivers an impressive specific capacity (384.3 mA h g-1 after 100 cycles at 100 mA g-1) and cycle stability (267 mA h g-1 after 125 cycles at 1 A g-1) for sodium storage. As evidenced by experiments and density functional theory calculations, abundant Mo vacancies in MoS2 can greatly accelerate the charge transfer and enhance the interaction between MoS2 and sodium, resulting in the promotion of sodium storage. Kinetic analysis result reveals that the ultrafast sodium ion storage of HMF-MoS2 could be associated with the significant contribution of capacitive energy storage. This work highlights the detailed molecular level understanding of chemical reaction on MoS2 surface by defect and morphology engineering, which can be applied to other metal sulfides for energy storage devices.

Efficient electrocatalysts are of great importance in improving the water splitting efficiency. Herein, we develop a self-templating strategy to construct porous iron cobalt (oxy)phosphide (Fe–Co–P) nanoboxes as promising pre-catalysts for the oxygen evolution reaction in alkaline solution. The constructed Fe–Co–P nanoboxes exhibit excellent electrocatalytic activity and afford a current density of 10 mA cm−2 at a small overpotential of 269 mV. Moreover, the structural evolution of the metal phosphides in the oxygen evolution process has been well monitored. X-ray absorption near-edge structure analyses and computational studies reveal that the structural merits and the effective intramolecular electronic coupling between the Fe and Co atoms via P/O bridges are responsible for the greatly improved electrocatalytic activity.

A cocatalyst is necessary for boosting the electron-hole separation efficiency and accelerating the reaction kinetics of semiconductors. As a result, it is of critical importance to in situ track the structural evolution of the cocatalyst during the photocatalytic process, but it remains very challenging. Here, atomically dispersed Ru atoms are decorated over multi-edged TiO2 spheres for photocatalytic hydrogen evolution. Experimental results not only demonstrate that the photogenerated electrons can be effectively transferred to the isolated Ru atoms for hydrogen evolution but also imply that the TiO2 architecture with multi-edges might facilitate the charge separation and transport. The change in valence and the evolution of electronic structure of Ru sites are well probed during the photocatalytic process. Specifically, the optimized catalyst produces the hydrogen evolution rate of 7.2 mmol g-1 hour-1, which is much higher than that of Pt-based cocatalyst systems and among the highest reported values. Ministry of Education (MOE) Published version X.W.L. acknowledges the funding support from the Ministry of Education of Singapore through the Academic Research Fund (AcRF) Tier-2 grant (MOE2017-T2-2-003) and Tier-1 grants (RG110/17; RG116/18).

Recently, molybdenum sulfide with its amorphous counterpart was found to hold a high activity versus the hydrogen evolution reaction (HER), making it a high potential material to explore new HER catalysts. Here we present a facile chemical method to synthesize ultra-small freestanding amorphous molybdenum sulfide (a-MoSx) colloidal nanodots with diameter of lower than 2 nm. Electrocatalytic HER tests show that freestanding a-MoSx colloidal nanodots exhibit an enhanced catalytic hydrogen activity in stark in contrast with in-situ annealed c-MoS2. When applied as a co-catalyst in photocatalytic HER, ultra-small a-MoSx nanodots could form a compact interface with the TiO2 when assisted by a bifunctional molecular linker, as the mercaptopropionic acid (MPA), which facilitates the decrease of the interfacial Schottky barrier occurring between the two components and allows for a fast injection of photo-excited electrons from the photoharvester into the co-catalyst. Our results demonstrate that the drastic enhancement of the photocatalytic H2 promotion rate of a-MoSx@MPA-TiO2 is mainly provided by unsaturated Mo(IV) active sites generated by the in-situ reduction during the photocatalytic HER process. The synergistic effect of generated unsaturated Mo(IV) sites and the presence of more exposed intrinsic active edges further promotes the enhancement of the catalytic H2 activity on a-MoSx nanodots.

The catalysts for lithium-oxygen batteries have been researched for decades due to the huge energy storage ability. However, the sluggish catalytic performance towards the decomposition of discharge products (Li2O2) inspires us to utilize the photo-generated holes to overcome the obstacle. As novel energy storage device, the TiO2 nanorod arrays on carbon textiles were well-designed and adopted as both air cathode and photo-anode for photo-assisted Li-O2 batteries. Electrochemical data strongly demonstrate that the abundant photo-generated holes on the TiO2 can efficiently oxidize the Li2O2 (the charge potential reduced from 4.31 V to 2.86 V vs Li/Li+). It is noted that the light illumination prompts the TiO2 to be more defective and the generated oxygen vacancies further enhance the electron and Li+ migration, leading to the improved ORR performance (discharge potential at 2.85 V vs Li/Li+). The batteries can charge/discharge for 30 cycles with no decay and deliver the excellent rate performance.

Interface engineering is a promising strategy for boosting the catalytic performances via the optimized coordination. Herein, we developed a top-down strategy to in situ obtain the nanocomposite of N, S-decorated porous carbon matrix encapsulated WS2/W2C (WS2/W2C@NSPC). The as-synthesized hybrid is characterized by excellent interface coupling in atomic level, good electrical conductivity, and high active surface area. Electrochemical measurements show that the optimized catalyst exhibits remarkable electrocatalytic activity for hydrogen evolution in both acidic and alkaline media. These results should be attributed to the abundant active sites existing in the different phase boundaries, resulting from a synergistic effect of the activated WS2/W2C heterostructure and the highly conductive carbon matrix. This strategy opens new avenues toward understanding the relationship between chemical structure and catalytic performance in molecular level and thus providing a rational way to fabricate highly efficient...

BIF-20, a zeolite-like porous boron imidazolate framework with high density of exposed B–H bonding, is combined with graphitic carbon nitride (g-C3N4) nanosheets via a facile electrostatic self-assembly approach under room temperature, forming an elegant composite BIF-20@g-C3N4 nanosheet. The as-constructed composite preferably captures CO2 and further photoreduces CO2 in high efficiency. The photogenerated excitations from the carbon nitride nanosheet can directionally migrate to B–H bonding, which effectively suppresses electron–hole pair recombination and thus greatly improves the photocatalytic ability. Compared to the g-C3N4 nanosheet, the BIF-20@g-C3N4 nanosheet composite displayed a much-enhanced photocatalytic CO2 reduction activity, which is equal to 9.7-fold enhancements in the CH4 evolution rate (15.524 μmol g–1 h–1) and 9.85-fold improvements in CO generation rate (53.869 μmol g–1 h–1). Density functional theory simulations further prove that the presence of B–H bonding in the composite is fav...

Herein a simple approach is proposed to greatly improve the photocatalytic performance of a porphyrinic metal organic framework (PCN-224) by implantation of coordinatively unsaturated Fe(III) sites into the porphyrin unit. Taking the photooxidation of isopropanol (IPA) as a model reaction, the newly developed Fe@PCN-224 exhibits significantly enhanced photocatalytic activity, which is equivalent to an 8.9-fold improvement in acetone evolution rate and 9.3-fold enhancements in CO 2 generation rate compared with the PCN-224. Mechanism investigation reveals that the presence of Fe(III) sites in the PCN-224 can not only greatly boost the electron–hole separation efficiency, but also effectively convert the in-situ photogenerated inactive H 2 O 2 into reactive oxygen-related radicals via Fenton reactions to participate in the photocatalytic IPA oxidation. The enhanced photocatalytic activity for IPA oxidation is also observed over another Fe(III) implanted porphyrinic metal organic framework (Fe@PCN-222), suggesting the generality of this strategy.

Here we realize the decoration of isolated platinum atoms onto the surface step of CdS nanowires. The single-atom co-catalyst with high stability can realize maximum atom efficiency and significantly boost electron-hole separation efficiency in chromophore units, generating a greatly enhanced photocatalytic hydrogen evolution performance, 7.69 times as high as Pt nanoparticles do and 63.77 times higher than that of bare CdS nanowires. Directional migrations of photogenerated excitons from the conduction band of CdS to catalytic platinum centers have been witnessed by transient absorption spectroscopy, leading to the supply of long-lived electrons for highly efficient photocatalytic hydrogen evolution. Density functional theory calculations further confirm that the excellent catalytic performance is associated with positively charged platinum sites with partially vacant 5d orbitals, which change distribution of charge density and facilitate higher excited carrier density.

Graphitic carbon nitride (g-C3N4) is an actively investigated metal-free photocatalyst for solar energy conversion. However, primary g-C3N4 usually exhibits limited utilization of visible light and fast combination of photoexcited charge carriers, resulting in low photocatalytic H2 evolution activity. Defect-modified g-C3N4 shows much enhanced photocatalytic H2 evolution activity owing to extended light absorption as well as efficient charge separation and transfer. Here, the photocatalyst simultaneously containing nitrogen vacancies and O-doping is successfully developed by using a two-step post-synthetic strategy for photocatalytic H2 evolution, resulting in a greatly-boosted H2 evolution activity (1.69 × 103 μmol g-1 h-1) compared with that of pristine g-C3N4 (1.12 × 102 μmol g-1 h-1). It is believed that the newly developed double-defect strategy may open an avenue toward obtaining molecular level comprehension of the function of a catalyst in photocatalytic H2 evolution and can be extended to the modification of other semiconductors.

Interface modification is an effective and promising route for developing functional electrocatalysts. However, researchers have not created a reliable method to optimize the interfaces of components existing in electrocatalysts, although it is very crucial for the technological development of high-performance electrodes. Here, we develop a strategy aiming at the in situ anchorage of Co9S8 nanoparticles into a nitrogen (N), sulfur (S) co-implanted three-dimensional carbon matrix (Co9S8@NSCM) as a highly active and durable nonprecious metal electrocatalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline medium. This strategy offers an opportunity to optimize the interface interaction and affords high activity for the ORR and OER in terms of low overpotentials and high current intensities. In addition, by confining Co9S8 nanoparticles into a N,S-doped carbon matrix, corrosion and aggregation can be effectively prevented, and thus the catalyst exhibits nearly unfading ORR catalytic performance after 100 000 s testing, a low discharge–charge voltage gap (0.81 V) and a long cycle life (up to 840 cycles) in Zn–air batteries. The present work highlights potentially powerful interface engineering for designing multi-component heterostructures with advanced performances in oxygen electrochemistry and related energy conversion.

Precisely constructed dispersion of well-defined single-atom active centers on the semiconductor could allow of the investigation of reaction mechanisms, yet targeted delivery of solar energy to steer the charge kinetics for hydrogen evolution remains challenging. Here we realize the location of isolated Co atoms on the TiO2 nanosheets with the thickness of 6 nm, providing highly active catalytic sites for the significantly boosted photocatalytic hydrogen evolution. X-ray absorption fine structure measurements verify that the atomically dispersed Co is successfully grafted on the surface of TiO2 nanosheets. Experimental exploration and theoretical demonstration not only confirm the isolated Co atoms perform as reactive sites, but also verify that the electron transfer and hydrogen adsorption/desorption processes can be greatly accelerated via the effective Co-O electronic coupling in atomic scale, thereby facilitating the hydrogen evolution.

Summary Exploring novel functional materials is of vital importance in the development of science and technology, and thus beneficial to our daily life. Metal-organic frameworks (MOFs) and their composites as well as derivatives, with high porosity and tailorable chemical components, have drawn increasing interest in gas storage, energy conversion, and environment remediation in the past decades. This review highlights recent achievements on applications of MOF-based materials in the renewable energy and environmental science. Specifically, the developments and advantages of MOF-based materials are first presented and discussed. We then focus on the fabrication strategies of MOF-based materials and their applications in areas including gas adsorption, energy conversion, and storage. The well-established findings provide an in-depth understanding for the construction and application of these advanced materials. This review concludes with some outlooks for the fields of energy conversion and environmental science by using MOF-based materials.

A covalently linked reaction center/antenna hybrid composed of Co-porphyrin and low-molecular-weight carbon nitride was developed for the reduction of CO2 into CO under visible light for the first time. The hybrids possessed thirteen-fold higher photocatalytic activity (17 μmol/g/h) compared with bulk carbon nitride, and it is more than twice what it was in the Co-porphyrin loaded C3N4 heterojunction system. The efficient electron transfer and trapping by the Co active sites as well as the affinity of Co-porphyrin for CO2 are considered to account for the enhanced activity. Our findings may open a promising route to modify carbon nitride and provide a feasible approach to immobilize the active site into the light-harvest antenna for efficient electron-hole separation, electron transferring and the following redox reaction in photocatalytic process, which reforms the conventional semiconductor-cocatalyst heterojunction system.

We report that a covalent compound, boron phosphide (BP), can function as a highly stable and metal-free photocatalyst to produce hydrogen from water in the presence of sacrificial agents under visible light irradiation, even at extreme conditions such as strong acid and alkali. The BP photocatalyst is an n-type semiconductor and possesses highly chemical stability, which is resistant to corrosion by hot concentrated mineral acids (concentrated HCl, H2SO4, HNO3, and aqua regia) and aqueous alkali solution, offering new opportunities in the field of artificial photosynthesis.

Hybrid zeolitic imidazolate frameworks (HZIFs) possess the characteristics of both ZIFs and inorganic zeolites, attracting tremendous attention for their potential applications in electrochemical energy storage and conversion. This mini review presents design strategies for constructing advanced electrochemical functional materials based on Mo/W-based HZIF precursors/templates, and mainly focus on the component manipulation, morphology control, and the favored electrochemical reactions. The Mo/W-based HZIFs and their derivatives with a tailored composition and structure display excellent activity and stability for a broad electrochemical energy-related application. These summarized systematic strategies and perspectives offer inspiration and guidance for the future development of HZIF-based hybrids for more efficient and durable electrochemical energy applications.

Exploring highly efficient electrocatalysts for the oxygen evolution reaction (OER) and unveiling their activity origin are pivotal for energy conversion technologies. Herein, atomically distributed Ni sites over a N-doped hollow carbon matrix are reported as a promising electrocatalyst for OER in alkaline conditions. Significantly boosted activity is observed after the decoration of the active Ni sites with well-controlled coordination geometry. Results of X-ray absorption spectroscopy investigation and density functional theory (DFT) calculation reveal that the effective electronic coupling via the Ni-N coordination can move down the Fermi level and lower the adsorption energy of intermediates, thus resulting in the facilitated OER kinetics. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore) Accepted version

To enhance the performance of semiconductor photocatalysts, cocatalysts are used to accelerate surface reactions. Herein, ultrasmall molybdenum–oxygen (MoOx) clusters are developed as a novel non-noble cocatalyst, which significantly promotes the photocatalytic hydrogen generation rate of CdS nanowires (NWs). As indicated by extended X-ray absorption fine structure analysis, direct bonds are formed between CdS NWs and MoOx clusters, which guarantee the migration of photo-generated charge carriers. Moreover, the MoOx clusters induce deep electron trap states owing to the unique atomic arrangement and configuration with the generation of long-lived electrons to enhance the activity. These findings may guide the design of efficient cocatalytic materials for solar water splitting and open a new avenue toward practical applications of ultrasmall clusters. H.Z. and P.Z. contributed equally to this work. X.W.L. acknowledges the funding support from the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry, & Energy (MOTIE) of the Republic of Korea through the grant (No. 20168510050080).

Through a facile and effective strategy by employing lithium molten salts the controlled synthesis of 2H- and 1T-MoS2 monolayers with high-yield production is achieved. Both phases of MoS2 monolayers exhibit high stabilities. When used as a catalyst for hydrogen evolution, these phased MoS2 monolayers deliver respective advantages in the field of electro- and photo-catalytic hydrogen evolution.

A series of rod-like porous graphitic-carbon nitrides (short as CNs) with enhanced in-plane ordering have been fabricated through self-assembled heptazine hydrate precursors for the first time. By controlling the calcination of the preformed precursors with different temperature-rising rates, the resulted CNs (SAHEP-CNs-1) with the most ordered and least stacked graphitic planar are showing a tremendously improved hydrogen evolution rate of 420 μmol h−1 under visible light and a remarkable apparent quantum efficiency of 8.9% at 420 nm, which is among the highest values for C3N4-related photocatalysts in the literature. This work discloses that enhancing in-plane ordering is one critical factor for improving the photocatalytic H2 evolution of carbon nitride, which is an effective solution to prolong the lifetime of charge carriers by accelerating the charge transport and separation within the graphitic planar. This finding would present a facial strategy for the designing of efficient organic semiconductors for photocatalysis.

Graphitic carbon nitride (g-C3N4) has recently emerged as an attractive photocatalyst for solar energy conversion. However, the photocatalytic activities of g-C3N4 remain moderate because of the insufficient solar-light absorption and the fast electron–hole recombination. Here, defect-modified g-C3N4 (DCN) photocatalysts, which are easily prepared under mild conditions and show much extended light absorption with band gaps decreased from 2.75 to 2.00 eV, are reported. More importantly, cyano terminal CN groups, acting as electron acceptors, are introduced into the DCN sheet edge, which endows the DCN with both n- and p-type conductivities, consequently giving rise to the generation of p–n homojunctions. This homojunction structure is demonstrated to be highly efficient in charge transfer and separation, and results in a fivefold enhanced photocatalytic H2 evolution activity. The findings deepen the understanding on the defect-related issues of g-C3N4-based materials. Additionally, the ability to build homojunction structures by the defect-induced self-functionalization presents a promising strategy to realize precise band engineering of g-C3N4 and related polymer semiconductors for more efficient solar energy conversion applications.

Poor adsorption of reactants and intermediates as well as low mineralization rate greatly restrict the application of common semiconductor photocatalyst TiO2 for air purification. A plausible solution would be to integrate metal–organic frameworks (MOFs) materials with good gas adsorption property with traditional photocatalytic material TiO2 with exciton generation. A core–shell structured photocatalyst with functional MOFs HKUST-1 (Cu3(BTC)2, BTC = 1,3,5 benzenetricarboxylate) as core and porous ultrathin anatase film as shell was synthesized. The composite photocatalyst was characterized in detail, and isopropanol degradation experiments were performed to evaluate the photocatalytic performances. The experimental results revealed that HKUST-1 can provide a special pathway for photogenerated electrons migration and thus restrain the recombination of electrons and holes to increase the photocatalytic efficiency. Furthermore, the capture of reactants and intermediates was also enhanced due to the unique M...

A simple method is developed to fabricate protonated porous graphitic carbon nitride nanosheets (P-PCNNS) by protonation-exfoliation of bulk graphitic carbon nitride (BCN) with phosphoric acid (H3 PO4 ). The H3 PO4 treatment not only helps to exfoliate the BCN into 2D ultrathin nanosheets with abundant micro- and mesopores, endowing P-PCNNS with more exposed active catalytic sites and cross-plane diffusion channels to facilitate the mass and charge transport, but also induces the protonation of carbon nitride polymer, leading to the moderate removal of the impurities of carbon species in BCN for the optimization of the aromatic π-conjugated system for better charge separation without changing its chemical structure. As a result, the P-PCNNS show much higher photocatalytic performance for hydrogen evolution and CO2 conversion than bare BCN and graphitic carbon nitride nanosheets.

Au-based catalysts were widely applied in photocatalytic areas owing to Au local surface plasmon resonance (LSPR), especially in the reactions of secondary alcohol dehydrogenation. However, there were rare cases reporting Au catalysts to dehydrogenate secondary alcohols under dark condition at room temperature. In this work, basic semiconductor birnessite, with easily extractable lattice oxygen in its lattice structure, was employed as support of Au catalyst and it was found that the Au/birnessite catalyst could dehydrogenate iso-propanol (IPA) to acetone under dark condition (3.7 μmol acetone was produced within 5 h). With the utilization of lattice oxygen in the reaction under dark condition, oxygen vacancies were instantaneously formed which enhanced the light absorbing properties of Au/birnessite and further improved its photocatalytic activity (13.6 μmol acetone production within 5 h). The synergistic effects between lattice oxygen and oxygen vacancies enhanced the performance of Au-based catalyst in IPA dehydrogenation and this work provides a synthesis tactic for effective catalysts in the dehydrogenation of various secondary alcohols.

Highly efficient utilization of solar light with an excellent reduction capacity is achieved for plasmonic Fe@C nanostructures. By carbon layer coating, the optimized catalyst exhibits enhanced selectivity and stability applied to the solar-driven reduction of CO2 into CO. The surface-plasmon effect of iron particles is proposed to excite CO2 molecules, and thereby facilitates the final reaction activity.

Photocatalysis has been distinguished itself as one of the most promising technologies from the wide variety of renewable energy projects underway, as it represents a promising approach to realize solar energy conversion. Under light irradiation, semiconductors (TiO 2 , Ag 3 PO 4 , WO 3 , CdS, and ZnS etc.) have demonstrated great potential in photolysis of water to yield hydrogen fuel, decomposition or oxidization of hazardous substances, photoelectrochemical conversion, as well as artificial photosynthesis. However, the disadvantages of easy agglomeration, and low solar energy conversion efficiency of these inorganic catalysts limit their large scale applications. Developing new photocatalysts has been attracting great attention in the related research communities. Owing to their structural diversity and controllable synthetic procedures, coordination polymers (CPs) provide a newly emerging platform to organize light-harvesting antennae and catalytic centers to achieve solar energy conversion. Besides, controllable integration of CPs with functional materials is leading to the creation of new multifunctional composites/hybrids, which exhibit superior photocatalytic performances to those of the individual components due to the collective behavior of the functional units. In this article, the latest advances of CPs based materials in the application of photocatalysis are critically reviewed, and the main approaches for efficient light harvesting and active site engineering in CPs-based photocatalysts are discussed. The main advantages of CPs as photocatalysts and the challenges faced for further improving catalytic performance are also highlighted.

Two three-dimensional (3-D) MOFs, [(C2H5)4N)]3[H3O]2[Cd6Br(H2-DHBDC)8(DMF)4] (1; H4-DHBDC=2,5-dihydroxy-1,4-benzenedicarboxylic acid, DMF=N,N-dimethylformamide) and [(CH3)2NH2]2[Cd3(H2-DHBDC)4(DMF)2]·2DMF(2), are prepared from the self-assembly reactions between Cd(CH3COO)2 and H4-DHBDC, respectively. Both anionic frameworks consist of linear trinuclear Cd units (e.g., 1: [Cd3BrO2(CO2)7] and [Cd3O2(CO2)8]; 2: [Cd3O2(CO2)8]) linked by the H2-DHBDC ligands. The photoluminescent properties of compound 1 are tunable through cation-exchange with different metal ions. The results demonstrated an effective ion-exchange approach toward the functional modification of MOF materials.

Finding a highly efficient, selective and economic approach for electrochemical reduction of aqueous carbon dioxide is a great challenge in realizing an artificial system for a sustainable carbon cycle. Novel mesoporous palladium–copper bimetallic electrocatalysts with superior activity and high faradaic efficiencies (FEs) are reported for the first time. The mesoporous nanostructure provides a roughened surface which is abundant in active sites and promotes selective conversion of CO2 to CO. First-principles calculations exhibit that Pd atoms on the catalyst surface serve as reactive centers and highly selective CO formation is attributed to the geometric and electronic effects within the palladium–copper bimetallic alloys. The CO2 and COOH* intermediate adsorption ability and the CO desorption ability on Pd atoms are effectively enhanced in the presence of Cu. Our results provide wide ranging implications for further improving the design and preparation of CO2 reduction electrocatalysts.

In the last few years, Ln-MOFs, which are stable multi-dimensional frameworks composed of highly luminescent Ln3+ ions and multitopic organic ligands, have become a very fascinating class of materials in view of their luminescence properties. Their luminescence can be easily modulated owing to their structural diversity and predictability, as well as multiple options for excitation and emission, including those performed via the organic linker serving as an efficient antenna, the discrete energy levels of Ln3+ ions, and the luminescent guests that were trapped in the cavities. In particular, the similarity in the chemical reactivity and the coordination environment of different Ln3+ ions allows the formation of a series of isostructural mixed Ln-MOFs whose colour output can be fine-tuned by changing the types and relative concentration of the constituent Ln3+ ions or the excitation wavelength. Most significantly, white-light emitting materials may be obtained if the mixing of Ln3+ ions can be carefully controlled. Based on these unique properties, mixed Ln-MOFs may play an outstanding role in the fields of lighting and display systems. The aim of this review is to provide an overview of the current status of the research on mixed Ln-MOFs, especially those constructed using aromatic polycarboxylate ligands, and to highlight their colour tunable and white light emission properties.

An Au/SrTiO3 catalyst with basic properties (Au/SrTiO3–urea) was reported for the first time to be efficient for the dehydrogenation of secondary alcohols at room temperature, with iso-propanol (IPA) dehydrogenation as the probe reaction. Different from previous reports that Au/SrTiO3 was generally regarded as only a photocatalyst in the IPA dehydrogenation reaction, in this work, it was found that Au/SrTiO3–urea could also catalyse the reaction at room temperature without light irradiation, with an acetone production rate of 8.2 μmol h−1 (IPA conversion of 41.0%) which was more than 10 times higher than that of Pt/TiO2 evaluated under the same conditions. Characterization results revealed that the lattice oxygen in SrTiO3 was involved in the reaction through the Mars-van Krevelen mechanism, while Au facilitated the cleavage of C–H bonds of the adsorbed reactant with the assistance of a base. Its catalytic activity was further increased to 16.5 μmol h−1 (IPA conversion of 82.5%) after the introduction of visible light. It is regarded that the photon induced photocatalytic performance was significantly enhanced with the existence of instantaneously generated oxygen vacancies. Additionally, the conversion of IPA (82.5%) and the rate of acetone production over Au/SrTiO3–urea (16.5 μmol h−1) after visible light irradiation for 1 h were 12.3 times and 2.5 times as high as those over Au/P25 (IPA conversion of 6.7% and acetone production rate of 6.7 μmol h−1), a catalyst which was also reported to be active in IPA dehydrogenation without light irradiation. This study provides a method for designing efficient catalysts for the dehydrogenation of secondary alcohols at room temperature.

Metal-organic frameworks (MOFs) are attracting considerable attention for their use as both the precursor and the template to prepare metal oxides or carbon-based materials. For the first time in this paper, the core-shell ZIF-8@ZIF-67 crystals are thermally converted into porous ZnO@Co3O4 composites by combining a seed-mediated growth process with a two-step calcination. The designed porous ZnO@Co3O4 composites exhibited the highest photocatalytic activity with an excellent stability for the reduction of CO2 among the commonly reported composite photocatalysts. Their superior photocatalytic performance is demonstrated to be resulting from the unique porous structure of ZnO@Co3O4 and the co-catalytic function of Co3O4 which can effectively suppress the photocorrosion of ZnO.

Metal-organic framework (MOF)-based energetic material [Cu3 (MA)2 (N3 )3 ] (1; MA=melamine) was synthesized and structurally characterized (47.55 % N). The structural analysis revealed the existence of unusual multiwalled tubular channels and interweaving of single and double helical units in 1. The standard molar enthalpy of formation was found to be 1788.73 kJ mol(-1) , which is the highest value among previously reported MOF-based energetic materials. The calculated detonation properties showed that 1 can be used as a potential explosive. Sensitivity tests revealed that 1 is insensitive and thus can function as a high-energy-density material with a favorable level of safety.

The emergence of Mo-based hybrid zeolitic imidazolate frameworks (HZIFs) with MoO4 units brings substantial advantages to design and synthesize complex Mo-based electrocatalyst that are not expected in their conventional synthesis path. Herein, as a newly proposed concept, a facile temperature-induced on-site conversion approach (TOCA) is developed to realize the transformation of MoO4 units to C-Mo-S triatomic coordination in hierarchical hollow architecture. The optimized hybrid (denoted as MoCSx 1000) shows accelerating oxygen reduction reaction (ORR) kinetics and excellent stability, which are superior to the most reported Mo-based catalysts. Extended X-ray adsorption fine structure (EXAFS) analysis and computational studies reveal that the near-range electronic steering at C-Mo-S triatomic-coordinated nanointerface guarantees moderate ORR intermediates adsorption and thus is responsible for the boosted ORR activity. This work sheds light on exploring the intrinsic activity of catalysts by interfacial electronic steering.

High-performance catalysts for electrocatalytic and photoelectrochemical water splitting hold great promise for renewable energy conversion and storage. Herein, using porous N-doped carbon supported Au nanoparticles as catalysts, we demonstrate that the photon-induced localized surface plasmon resonance (LSPR) excitation on Au nanoparticles dramatically improves the hydrogen evolution reaction (HER), leading to a more than 4-fold increase of current and meanwhile affording a markedly decreased overpotential of 99 mV at a current density of 10 mA cm−2. The HER enhancement can be largely attributed to the efficient charge transfer of N-doped carbon that fastens the injection of hot electrons from plasmonic Au nanoparticles. This study highlights the increase of HER catalysis efficiency by plasmonic excitation and could provide new avenues towards the design of higher energy conversion catalytic water splitting systems with the assistance of light energy.

Surface modulation at the atomic level is an important approach for tuning surface chemistry and boosting the catalytic performance. Here, a surface modulation strategy is demonstrated through the decoration of isolated Ni atoms onto the basal plane of hierarchical MoS2 nanosheets supported on multichannel carbon nanofibers for boosted hydrogen evolution activity. X-ray absorption fine structure investigation and density functional theory (DFT) calculation reveal that the MoS2 surface decorated with isolated Ni atoms displays highly strengthened H binding. Benefiting from the unique tubular structure and basal plane modulation, the newly developed MoS2 catalyst exhibits excellent hydrogen evolution activity and stability. This single-atom modification strategy opens up new avenues for tuning the intrinsic catalytic activity toward electrocatalytic water splitting and other energy-related processes. NRF (Natl Research Foundation, S’pore) Accepted version

Adjusting the electronic structure of the active center is a highly effective strategy for improving the performance of catalysts. Herein, we report an atomically dispersed catalyst (FeCl1N4/CNS), which realized for the first time a great improvement of the ORR by controlling the electronic structure of the central metal with a coordinated chlorine. The half-wave potential of FeCl1N4/CNS is E1/2 = 0.921 V, which is the highest among the reported values for non-precious metal electrocatalysts and far exceeds that of FeN4/CN and commercial Pt/C in alkaline solution. Besides an exceptionally high kinetic current density (Jk) of 41.11 mA cm−2 at 0.85 V, it also has a good methanol tolerance and outstanding stability. Experiments and DFT demonstrated that the near-range interaction with chlorine and the long-range interaction with sulfur of Fe modulated the electronic structure of the active site, thus resulting in a great improvement of the ORR in alkaline media. The present findings could open new avenues for the design of superior electrocatalysts.

Platinum single atoms are loaded into mesoporous carbon spheres to give high electrocatalytic performance for hydrogen generation., Constructing atomically dispersed platinum (Pt) electrocatalysts is essential to build high-performance and cost-effective electrochemical water-splitting systems. We present a novel strategy to realize the traction and stabilization of isolated Pt atoms in the nitrogen-containing porous carbon matrix (Pt@PCM). In comparison with the commercial Pt/C catalyst (20 weight %), the as-prepared Pt@PCM catalyst exhibits significantly boosted mass activity (up to 25 times) for hydrogen evolution reaction. Results of extended x-ray absorption fine structure investigation and density functional theory calculation suggest that the active sites are associated with the lattice-confined Pt centers and the activated carbon (C)/nitrogen (N) atoms at the adjacency of the isolated Pt centers. This strategy may provide insights into constructing highly efficient single-atom catalysts for different energy-related applications.

Photocatalytic reduction of carbon dioxide (CO2) is attractive for the production of valuable fuels and mitigating the influence of greenhouse gas emission. However, the extreme inertness of CO2 and the sluggish kinetics of photoexcited charge carrier transfer process greatly limit the conversion efficiency of CO2 photoreduction. Herein, we report that the plasmonic coupling effect of Pt and Au nanoparticles (NPs) profoundly enhances the efficiency of CO2 reduction through dry reforming of methane reaction assisted by light illumination, reducing activation energies for CO2 reduction ∼30% below thermal activation energies and achieving a reaction rate 2.4 times higher than that of the thermocatalytic reaction. UV–visible (vis) absorption spectra and wavelength-dependent performances show that not only UV but also visible light play important roles in promoting CO2 reduction due to effective localized surface plasmon resonance (LSPR) coupling between Pt and Au NPs. Finite-difference time-domain simulations...

The photoreduction of CO2 is attractive for the production of renewable fuels and the mitigation of global warming. Herein, we report an efficient method for CO2 reduction over elemental boron catalysts in the presence of only water and light irradiation through a photothermocatalytic process. Owing to its high solar-light absorption and effective photothermal conversion, the illuminated boron catalyst experiences remarkable self-heating. This process favors CO2 activation and also induces localized boron hydrolysis to in situ produce H2 as an active proton source and electron donor for CO2 reduction as well as boron oxides as promoters of CO2 adsorption. These synergistic effects, in combination with the unique catalytic properties of boron, are proposed to account for the efficiency of the CO2 reduction. This study highlights the promise of photothermocatalytic strategies for CO2 conversion and also opens new avenues towards the development of related solar-energy utilization schemes.

Modular optimization of metal–organic frameworks (MOFs) was realized by incorporation of coordinatively unsaturated single atoms in a MOF matrix. The newly developed MOF can selectively capture and photoreduce CO2 with high efficiency under visible-light irradiation. Mechanistic investigation reveals that the presence of single Co atoms in the MOF can greatly boost the electron–hole separation efficiency in porphyrin units. Directional migration of photogenerated excitons from porphyrin to catalytic Co centers was witnessed, thereby achieving supply of long-lived electrons for the reduction of CO2 molecules adsorbed on Co centers. As a direct result, porphyrin MOF comprising atomically dispersed catalytic centers exhibits significantly enhanced photocatalytic conversion of CO2, which is equivalent to a 3.13-fold improvement in CO evolution rate (200.6 μmol g−1 h−1) and a 5.93-fold enhancement in CH4 generation rate (36.67 μmol g−1 h−1) compared to the parent MOF.

Water splitting represents a promising technology for renewable energy conversion and storage, but it is greatly hindered by the kinetically sluggish oxygen evolution reaction (OER). Here, using Au-nanoparticle-decorated Ni(OH)2 nanosheets [Ni(OH)2-Au] as catalysts, we demonstrate that the photon-induced surface plasmon resonance (SPR) excitation on Au nanoparticles could significantly activate the OER catalysis, specifically achieving a more than 4-fold enhanced activity and meanwhile affording a markedly decreased overpotential of 270 mV at the current density of 10 mA cm(-2) and a small Tafel slope of 35 mV dec(-1) (no iR-correction), which is much better than those of the benchmark IrO2 and RuO2, as well as most Ni-based OER catalysts reported to date. The synergy of the enhanced generation of Ni(III/IV) active species and the improved charge transfer, both induced by hot-electron excitation on Au nanoparticles, is proposed to account for such a markedly increased activity. The SPR-enhanced OER catalysis could also be observed over cobalt oxide (CoO)-Au and iron oxy-hydroxide (FeOOH)-Au catalysts, suggesting the generality of this strategy. These findings highlight the possibility of activating OER catalysis by plasmonic excitation and could open new avenues toward the design of more-energy-efficient catalytic water oxidation systems with the assistance of light energy.

Single metal-organic frameworks (MOFs), constructed from the coordination between one-fold metal ions and organic linkers, show limited functionalities when used as precursors for nanoporous carbon materials. Herein, we propose to merge the advantages of zinc and cobalt metals ions into one single MOF crystal (i.e., bimetallic MOFs). The organic linkers that coordinate with cobalt ions tend to yield graphitic carbons after carbonization, unlike those bridging with zinc ions, due to the controlled catalytic graphitization by the cobalt nanoparticles. In this work, we demonstrate a feasible method to achieve nanoporous carbon materials with tailored properties, including specific surface area, pore size distribution, degree of graphitization and content of heteroatoms. The bimetallic-MOF-derived nanoporous carbon are systematically characterized, highlighting the importance of precisely controlling the properties of the carbon materials. This can be done by finely tuning the components in the bimetallic MOF precursors and thus designing optimal carbon materials for specific applications.

An overall PEC CO2 conversion was firstly reported by integrating both the newly designed metal cathode and the n-type photoanode with functional nanostructures. The maximum Faradaic efficiency (FE) for CO is ca. 75% at -1.2 V with incident photon-to-current conversion efficiency (IPCE) value of 16% at 340 nm.