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Molybdenum diselenide (MoSe2) has been considered as promising electrocatalysts for catalyzing the hydrogen evolution reaction (HER) due to its narrow band gap and appropriate adsorption free energy. However, its catalytic performance is still impeded by inferior electrical conductivity and insufficient active sites, thus leading to unsatisfactory HER performance. Herein, MoSe2@N-doped carbon (NC) hollow nanoflowers with interfacial Mo-N-C bonds were controllably fabricated through the in situ selenization of the self-polymerized Mo-polydopamine precursor. Benefiting from the unique hollow structure, NC protective layer, and intimate interfacial interaction, the optimal MoSe2@NC displays good HER performance with low overpotentials (175 and 183 mV) and long-term stability (up to 12 h at -10 mA cm-2) in 0.5 M H2SO4 and 1.0 M KOH solutions, respectively. The theoretical results show that Mo-N-C bonds at the interface of MoSe2@NC give rise to relatively low unoccupied eg orbital density of states and ideal H2 adsorption free energy. This work presented here highlights the critical role of interfacial chemical bonds in regulating the electronic structure of nanomaterials and further improving the HER performance.

The evolution of cost-effective hydrogen evolution reaction (HER) electrocatalysts is of great significance for the development of clean energy. Exploring effective synthesis strategies to optimize the performance of non-noble metal electrocatalysts has always attracted our attention. Herein, ultrathin coordination polymers were used as precursors to controllably synthesize two-dimensional (2D) ultrathin dual-phase transition metal selenide (TMSs)/carbon–nitrogen (CN) composites (CoSe2–NiSe2/CN) by a two-step method (first a low temperature hydrothermal method for selenization, and then high temperature calcination selenization). Benefiting from its large specific surface area (49 m2 g−1), abundant catalytically active sites and synergistic effects, CoSe2–NiSe2/CN can significantly enhance the HER catalytic activity and exhibits good electrocatalytic activity with an overpotential of 150 mV at −10 mA cm−2, and a small Tafel slope of 42 mV dec−1 in an acidic electrolyte for the HER. This work provides a new strategy for optimizing the HER catalytic activity of TMSs by preparing 2D ultrathin dual-phase TMS composite materials.

Facile preparation of cost-effective and durable porous carbon-supported non-precious-metal/nitrogen electrocatalysts for oxygen reduction reaction (ORR) is extremely important for promoting the commercialized applications of such catalysts. In this work, the FeCl3-containing porphyrinato iron-based covalent porous polymer (FeCl3·FePor-CPP) was fabricated in-situ onto porous corncob biomass supports via a simple one-pot method. Subsequent thermal-reduction pyrolysis at 700 °C–900 °C with CO2 gas as an activating agent resulted in Fe2O3-decorated and N-doped graphitic carbon composite Fe2O3@NCb NC = N-doped graphene analog; bio-C = the corncob-derived hierarchically porous graphitic biomass carbon framework). The derived α-Fe2O3 and γ-Fe2O3 nanocrystals (5–10 nm particle diameter) were all immobilized on the N-doped bio-C micro/nanofibers. Notably, the Fe2O3@NC&bio-C obtained at the pyrolysis temperature of 800 °C (Fe2O3@NC&bio-C-800), exhibited unusual ORR catalytic efficiency via a 4-electron pathway with the onset and half-wave potentials of 0.96 V and 0.85 V vs. RHE, respectively. In addition, Fe2O3@NC&bio-C-800 also exhibited a high and stable limiting current density of -6.0 mA cm−2, remarkably stability (larger than 91% retention after 10000s), and good methanol tolerance. The present work represents one of the best results for iron-based biomass material ORR catalysts reported to date. The high ORR activity is attributed to the uniformly distributed α-Fe2O3 and γ-Fe2O3 nanoparticles on the N-enriched carbon matrix with a large specific surface area of 772.6 m2 g−1. This facilitates favor faster electron movement and better adsorption of oxygen molecules on the surface of the catalyst. Nevertheless, comparative studies on the structure and ORR catalytic activity of Fe2O3@NC&bio-C-800 with Fe2O3@bio-C-800 and NC&bio-C-800 clearly highlight the synergistic effect of the coexisting Fe2O3 nanocrystals, NC, and bio-C on the ORR performance.

Adsorptive separation of acetylene (C2H2) from carbon dioxide (CO2) promises a practical way to produce high-purity C2H2 required for industrial applications. However, challenges exist in the pore environment engineering of porous materials to recognize two molecules due to their similar molecular sizes and physical properties. Herein, we report a strategy to optimize pore environments of multivariate metal-organic frameworks (MOFs) for efficient C2H2/CO2 separation by tuning metal components, functionalized linkers, and terminal ligands. The optimized material UPC-200(Al)-F-BIM, constructed from Al3+ clusters, fluorine-functionalized organic linkers, and benzimidazole terminal ligands, demonstrated the highest separation efficiency (C2H2/CO2 uptake ratio of 2.6) and highest C2H2 productivity among UPC-200 systems. Experimental and computational studies revealed the contribution of small pore size and polar functional groups on the C2H2/CO2 selectivity and indicated the practical C2H2/CO2 separation of UPC-200(Al)-F-BIM.

A series of cobalt and metal-free phthalocyanine ambipolar semiconductors, MPc[β/α-O(4-CF3-Ph)4] (M = Co, 2H) (1–4), are synthesized and fabricated into self-assembled microstructures. The Co[Pc(β/α-OPhCF3)4] (1 and 3) molecules formed one-dimensional (1D) nanoribbons (400–300 nm) with a larger width of 1 relative to 3, whereas the H2Pc[β/α-O(4-CF3-Ph)4] (2 and 4) molecules self-assembled into wider microbelts (5–4 μm) with 2 larger than 4, showing the effect of the M center and the substituent positions of the Pc rings on the dimensions of the microstructures. An increased crystallinity is revealed in the order of 4 < 3 < 2 < 1, resulting in an increased conductivity in the same order. Towards NO2 and NH3, both positive and negative current changes are found among the sensors 1–4, with the lowest limit of detection (LOD) as low as 3 ppb for NO2 and 420 ppb for NH3 from 1, while a positive current response to H2S is obtained only from 1 with a LOD of 100 ppb, respectively, achieving the best results for the room-temperature detection of NO2, NH3 and H2S gases based on all of the solution-processed phthalocyanine-based sensors reported so far. Accordingly, the sensor responses are dominated by both M-analyst interaction (M = Co, 2H) and conductivity among the sensors 1–4. In particular, different sensor arrays consisting of the sensor of 1 combined with one of the other three sensors of 2–4 are established. NO2, NH3 and H2S gases at ppb levels can be accurately identified by the combination of two parameters, namely current change direction and sensitivity.

The selective adsorption of APPT-Cd-MOF 1 for propyne, 2-butyne and phenylacetylene was confirmed by single-crystal analysis. In addition, the selective adsorption performance of Cd-MOF for C3H4/C3H6/C3H8 was investigated. The matching of the functionality and size/shape between porous materials and guest molecules clarified the specific recognition of 1 for linear alkyne molecules.

Two Co(II)-MOFs with different structures were successfully synthesized under the premise of designing two ligands containing alkynyl functional groups. Complexes 1 ([Co(TEPA)(TPT)2/3]·2DMF·H2O) and 2 ([Co(EPA)(TPT)]·1.5DMF·1.5H2O) show excellent luminescence properties. Meanwhile, as fluorescent sensors, complexes 1 and 2 exhibit selectivity and sensitivity for Fe3+ with the Ksv of 1.520 × 104 L/mol and 3.543 × 104 L/mol, which can rapidly detect nitroaromatic compounds in methanol and ethanol, especially for 2,4-NPH through fluorescence quenching with high quenching efficiency. In particular, the Ksv value of complexes 1 and 2 towards 2,4-NPH can reach up to 1.627 × 105 L/mol and 9.600 × 104 L/mol, demonstrating that complexes 1 and 2 are good candidates for the identification and detection of Fe3+ and nitroaromatic compounds.

Ethylene (C2H4) and propylene (C3H6) are important energy sources and raw materials in the chemical industry. Storage and separation of C2H4 and C3H6 are vital to their practical application. Metal–organic frameworks (MOFs) having adjustable structures and pore environments are promising candidates for C3H6/C2H4 separation. Herein, we obtained a Cu-based MOF synthesized by H3TTCA and pyrazine ligands. By adding different functional groups on the ligands within the MOFs, their pore environments are adjusted, and thus, the C3H6 storage capacity and C3H6/C2H4 separation efficiency are improved. Eventually, the fluoro- and methyl-functionalized iso-MOF-4 exhibits a better gas storage and C3H6/C2H4 separation performance compared with iso-MOF-1 (nonfunctionalized), iso-MOF-2 (fluoro-functionalized), and iso-MOF-3 (methyl-functionalized). A record-high C3H6 uptake of 293.6 ± 2.3 cm3 g–1 (273 K, 1 atm) is achieved using iso-MOF-4. Moreover, iso-MOF-4 shows excellent repeatability, and only 3.5% of C3H6 storage capacities decrease after nine cycles. Employing Grand Canonical Monte Carlo (GCMC) simulations, it is indicated that iso-MOF-4 preferentially adsorbs C3H6 rather than C2H4 at low pressure. Single-crystal X-ray diffraction on C3H6-adsorbed iso-MOF-4 crystals precisely demonstrates the adsorption positions and arrangement of C3H6 molecules in the framework, which is consistent with the theoretical simulations. Remarkably, gas sorption isotherms, molecular simulations, and breakthrough experiments comprehensively demonstrate that this unique MOF material exhibits highly efficient C3H6/C2H4 separation. Additionally, iso-MOF-4 also possesses efficient separation of C3H8/CH4 and C2H6/CH4, indicating its promising potential in storage/separation of light hydrocarbons in industry., Fine-tuning the pore environment through multifunctionalized ligand modification in an isoreticular Cu-MOF framework for optimal gas adsorption and separation is studied.

Pseudomorphic conversion of metal-organic frameworks (MOFs) enables the fabrication of nanomaterials with well-defined porosities and morphologies for enhanced performances. However, the commonly reported calcination strategy usually requires high temperature to pyrolyze MOF particles and often results in uncontrolled growth of nanomaterials. Herein, we report the controlled alkaline hydrolysis of MOFs to produce layered double hydroxide (LDH) while maintaining the porosity and morphology of MOF particles. The preformed trinuclear M3(μ3-OH) (M = Ni2+ and Co2+) clusters in MOFs were demonstrated to be critical for the pseudomorphic transformation process. An isotopic tracing experiment revealed that the 18O-labeled M3(μ3-18OH) participated in the structural assembly of LDH, which avoided the leaching of metal cations and the subsequent uncontrolled growth of hydroxides. The resulting LDHs maintain the spherical morphology of MOF templates and possess a hierarchical porous structure with high surface area (BET surface area up to 201 m2·g-1), which is suitable for supercapacitor applications. As supercapacitor electrodes, the optimized LDH with the Ni:Co molar ratio of 7:3 shows a high specific capacitance (1652 F·g-1 at 1 A·g-1) and decent cycling performance, retaining almost 100% after 2000 cycles. Furthermore, the hydrolysis method allows the recycling of organic ligands and large-scale synthesis of LDH materials.

A 3D microporous MOF [Cu1.5(BTB-NH2)(H2O)2]·6DMA·5H2O (UPC-99) of the (2,3,4-c)-net novel topology type was successfully constructed by the amino-functionalized ligand and Cu(II) ions via a solvothermal method. Due to the presence of two channels with open Cu(II) sites and –NH2 groups, UPC-99 exhibits a high adsorption selectivity of 15.3 for CO2/CH4 at 1 bar and 273 K. Remarkably, UPC-99 exhibits a significant adsorption difference in C3H6 and C3H8 relative to CH4 and shows a high separation selectivity for C3 light hydrocarbons relative to CH4 (496.7 for C3H6/CH4 and 410.5 for C3H8/CH4 at 273 K, 1 bar) by single-component gas sorption and selectivity calculations in IAST methods. Moreover, the presence of open Lewis acidic Cu(II) sites in the channels allows UPC-99 to exhibit excellent catalytic performance in the catalytic cycloaddition reactions of CO2 with epoxides.

The separation of ethylene (C2 H4 ) from a mixture of ethane (C2 H6 ), ethylene (C2 H4 ), and acetylene (C2 H2 ) at normal temperature and pressure is a significant challenge. The sieving effect of pores is powerless due to the similar molecular size and kinetic diameter of these molecules. We report a new modification method based on a stable ftw topological Zr-MOF platform (MOF-525). Introduction of a cyclopentadiene cobalt functional group led to new ftw-type MOFs materials (UPC-612 and UPC-613), which increase the host-guest interaction and achieve efficient ethylene purification from the mixture of hydrocarbon gases. The high performance of UPC-612 and UPC-613 for C2 H2 /C2 H4 /C2 H6 separation has been verified by gas sorption isotherms, density functional theory (DFT), and experimentally determined breakthrough curves. This work provides a one-step separation of the ternary gas mixture and can further serve as a blueprint for the design and construction of function-oriented porous structures for such applications.

The storage and separation of C2H2 and CO2 require specific porous materials having surfaces onto which C2H2 or CO2 molecular can be selectively adsorbed. Through the modification of a multifunctional ligand with −F, −Cl, −NH2, −CH3, −OCH3, and inorganic secondary building units (SBUs) with bipy-N ligands (dimethylamine, pyridine, 4-aminopyridine, and isonicotinic acid) based on a microporous Ni-MOF, the pore environment optimization is realized, achieving the enhancement of the adsorption and separation performances of C2H2 and CO2. The C2H2 uptakes vary from 178.4 to 130.1 cm3 g–1 and CO2 from 83.8 to 44.6 cm3 g–1 at 273 K and 1 atm. The 4-aminopyridine and dimethylamine modified UPC-110 has the highest C2H2/CO2 separation selectivity (5.1), further supported and explained via Grand Canonical Monte Carlo (GCMC) simulation and breakthrough experiments. Our work not only provides new porous materials for efficient C2H2 and CO2 storage but also contributes to the strategy on improving gas adsorption and se...

Four calcium(II) metal–organic frameworks, [Ca(BD)DMF]·DMF·H2O (1), [Ca2(EDDA)(H2O)2(DMA)]·3H2O (2), [Ca(TTD)(Diox)]·2H2O (3), and [Ca2(DBBD)(H2O)2(DMF)]·2DMF·H2O (4) were designed and constructed by using four different carboxylate ligands, i.e., [2,2′-bipyridine]-5,5′-dicarboxylic acid (H2BD), (E)-5,5′-(diazene-1,2-diyl) diisophthalic acid (H4EDDA), 2′,3′,5′,6′-tetramethyl-[1,1′:4′,1″-terphenyl]-4,4″-dicarboxylic acid (H2TTD), and (E)-4′,4‴-(diazene-1,2-diyl)bis(([1,1′-biphenyl]-3,5-dicarboxylic acid)) (H4DBBD), respectively (DMF = N,N-Dimethylformamide; DMA = Dimethylacetamide; Diox = 1,4-Dioxane). The differences in terms of lengths (6.95–17.68 A), steric hindrance and configurations among the four ligands lead to four different structures of the final calcium complexes. In addition, the solid-state fluorescence of all the complexes have been studied at room temperature, showing shifted maximum emission bands or enhanced fluorescent properties compared to that of free organic ligands.

Developing effective and robust electrocatalysts that are applicable for different pH conditions is promising for variable industrial hydrogen evolution reaction (HER), whereas it remains challenging for designing proper materials and protocols. Herein, we have developed a two-step electrodeposition-hydrothermal strategy to construct heterostructured binary Ni-W sulfides nanosheets based on carbon fiber (NiWS/CF). The electrodeposited nickel oxides film on CF in the first step is sulfurized and concurrently incorporated with tungsten disulfide in the following hydrothermal process. Benefiting from synergistic advantages of bimetallic sulfides as well as interwoven nanosheets for efficient mass/charge transport, the NiWS/CF electrode shows excellent HER performances over a broad pH range from acidic (pH = 0), neutral (pH = 7) to alkaline (pH = 14) media. The NiWS/CF electrode also presents stability in long-term electrolysis in wide PH range for at least 12 h, and its interlaced nanosheets structure are well maintained. Our work may provide general and promising strategies to obtain inexpensive and efficient electrocatalysts for pH-universal hydrogen production.

Based on the 5,10,15,20-tetra(cyanophenyl)porphyrin (CNTCPP) ligand, two supermolecule complexes formulated as [Cu(CNTCPP)]·2DMF (Cu-CNTCPP) and [Zn(CNTCPP)] (Zn-CNTCPP) have been synthesized and structurally characterized by single-crystal X-ray diffraction. Cu-CNTCPP features a 0 dimensional (0D) supramoleculer structure, whereas Zn-CNTCPP is a 2D structure. With coordination unsaturated points, Cu-CNTCPP exhibits electrocatalytic activity toward oxygen evolution reaction (OER) with low potential in 1.0 M KOH, generating a current density of 10 mA cm−2 at an potential of 1.66 V vs. RHE, which means it an efficient electrocatalytic material for OER.

The fluorescent Pb(II)–metal–organic nanotube, CD-MONT-2, which possesses a large {Pb14} metallamacrocycle, is synthesized by a modified biphasic liquid–solid–liquid (BLSL) strategy. This strategy takes advantage of solid cyclohexanol to avoid generation of by-products, and is suitable for producing CD-MONT-2 on a large scale. Importantly, water-stable CD-MONT-2 can be easily made into H2S test papers by coating a solution mixture of sodium carboxymethyl cellulose and CD-MONT-2′ on glass plates, which have the characteristics of high efficiency, rapidity, and visualization based on its fluorescence “turn-off” response. The CD-MONT-2 based visual test papers can be used without pretreatment and possess excellent sensitivity and stability.

The development of effective bifunctional catalysts for both oxygen reduction reactions (ORRs) and oxygen evolution reactions (OERs) is crucial for improving the performance of charge and discharge processes in rechargeable metal–air batteries. Here, we report a sulfonated cobalt phthalocyanine/carbon nanotube hybrid (CoPc-SO3H/CNT) prepared by a facile anchoring method along with sonication and magnetic stirring. The resulting CoPc-SO3H/CNT hybrid exhibits better catalytic activity for ORRs and OERs than the cobalt phthalocyanine/carbon nanotube hybrid (CoPc/CNT), sulfonated cobalt phthalocyanine (CoPc-SO3H), cobalt phthalocyanine (CoPc) and the carbon nanotube (CNT). The onset potential of CoPc-SO3H/CNT for the ORR in 0.1 M KOH is 0.88 V (vs. RHE), which is higher than that of CoPc/CNT (0.85 V), the CNT (0.80 V), CoPc-SO3H (0.77 V) and CoPc (0.66 V). Meanwhile, the CoPc-SO3H/CNT hybrid shows a much lower OER potential (1.62 V) at a current density of 10 mA cm−2 compared to CoPc-SO3H (1.64 V), CoPc/CNT (1.74 V), the CNT (1.96 V) and CoPc (>2.00 V) in 1 M KOH. Similar patterns are also found in 0.1 M KOH solution. Both the conductive CNT and the electron-withdrawing sulfonic groups are confirmed to benefit the electrochemical oxygen reactions (ORRs/OERs).

The simple and cost-efficient preparation of high-performance nitrogen-doped carbon aerogel (N-CA) for supercapacitors and other applications is still a big challenge. In this work, we have presented a facile strategy to synthesize hierarchically porous N-CA, which is based on solvothermal polymerization of phenol and formaldehyde under hypersaline condition with ethylenediamine (EDA) functioning as both a catalyst and a nitrogen precursor. Benefited from the catalytic effect of EDA on the polymerization, the obtained N-CA has a predominant amount of micropores (micropore ratio: 52%) with large specific surface area (1201.1 m2&middot, g&minus, 1). In addition, nitrogen doping brings N-CA enhanced wettability and reduced electrochemical impedance. Therefore, the N-CA electrode shows high specific capacitance (426 F&middot, 1 at 1 A&middot, 1 in 0.5 M H2SO4) and excellent cycling stability (104% capacitance retention after 10,000 cycles) in three-electrode systems. Besides, a high energy density of 32.42 Wh&middot, kg&minus, 1 at 800 W&middot, 1 can be achieved by symmetric supercapacitor based on the N-CA electrodes, showing its promising application for energy storage. Furthermore, N-CA also exhibits good capacity and long recyclability in the absorption of organic solvents.

The rational design of a highly reactive electronic structure as the active sites is crucial for the development of oxygen reduction reaction (ORR) catalysts. Herein, a unique ethynyl-linked sulfur-containing porphyrin organic polymer (S-POP) is firstly developed as a metal-free catalyst for ORR under acidic conditions, which possess intrinsic porous structures and easily accessible active sites for the adsorption of oxygen. The S-POP exhibits a superior ORR performance with onset potential of 0.82 V and half-wave potential of 0.72 V, achieving one of the best results among metal-free polymer-based ORR catalysts in acidic conditions, the high ORR activity of S-POP is attributed to the exposure of active sites under the test environment. In particular, it is discovered that after replacing pyrrole N by S atoms, the remaining aza N in S-POP exhibit higher ORR activity than those in conventional porphyrin organic polymer (POP). Density functional theory calculations shows that the significant improvement of S-POP over POP is from the redistribution and reduction of the density of charges on aza N, which promotes *O desorb process and decreases the overpotential. This work provides a novel guidance towards designing and modifying metal-free ORR electrocatalysts with a clear electronic structure as the active sites.

The assembly of a fluorescent dicarboxylate ligand with a barium ion resulted in the formation of a 3D metal-organic framework, Ba5(ADDA)5(EtOH)2(H2O)3·5DMF (UPC-17), based on a 1D rod-shaped secondary building unit. The unprecedented solvent-dependent sensitivities of UPC-17 for the detection of Fe(3+)/Al(3+) ions and 4-nitrophenol with high efficiency were observed for the first time. Significantly, UPC-17 exhibits superior "turn-off" detection for the Fe(3+) ion in methanol and acetone emulsions but shows "turn-on" detection in tetrahydrofuran emulsion. Furthermore, the visible color changes in the detection process make them easy to distinguish by the naked eye, which further increases its application potential.

A 3D non-interpenetrating porous metal-organic framework [Pb2(H2TCPP)]·4DMF·H2O (Pb-TCPP) (H6TCPP = 5,10,15,20-tetra(carboxyphenyl)porphyrin) was synthesized by employment of a robust porphyrin ligand. Pb-TCPP exhibits a one-dimensional channel possessing fairly good capability of gas sorption for N2, H2, Ar, and CO2 gases, and also features selectivity for CO2 over CH4 at 298 K. Furthermore, Pb-TCPP shows electrocatalytic activity for water oxidation in alkaline solution. It is the first 3D porous Pb-MOF that exhibits both gas adsorption properties and electrocatalytic activity for an oxygen evolution reaction (OER).

Three rigid, linear ligands, namely 2′,5′-dimethyl-[1,1′:4′,1′′-terphenyl]-4,4′′-dicarboxylic acid (H2L1), triphenyl-6,6′-dicarboxylic acid (H2L2), and 2,2′-bipyridine-5,5′-dicarboxylic acid (H2L3), were used for constructing metal–organic frameworks (MOFs) with Pb(II). With a similar nature of solvent conditions (DMF/EtOH, with different volumes' rates), four structurally diverse MOFs, namely, [Pb(L1)(DMF)] 1, [Pb(L1)(DMF)] 2, [Pb(L2)] 3, and [Pb3(L3)2(Cl−)2] 4, were synthesized and characterized by single-crystal X-ray diffraction, thermogravimetric analysis, elemental analysis, and powder X-ray diffraction measurements. As the numbers of the central benzene ring contained in the ligands changed from three to two, the length of the ligands varied from 15.64 A to 10.89 A, and steric functional groups endowed the three ligands with more variations, such as a 1D zigzag chain of 1, a 2D wave-like layer of 2, a 3D Pb–O–C-based layer of 3, and a 3D Pb–O–Cl-based chain of 4. Solid-state photoluminescence studies were carried out for all the complexes at room temperature.

Herein, a bimetallic MOF (Co/Fe-MOF) prepared by doping of Fe centers into a Co-MOF structure was explored as a bifunctional electrocatalyst for hydrogen evolution and oxygen evolution. The Fe-doping can greatly enhance the catalytic activity of Co/Fe-MOF, which presents much smaller overpotentials and Tafel slopes than the monometallic Co-MOF in 1.0 ​M KOH solution, and remarkable durability that superior to the corresponding commercial catalysts of Pt/C and RuO2 for both of the two processes. Impressively, the OER activity of Co/Fe-MOF is comparable to the RuO2 and even higher at current densities (≥10 ​mA ​m−2). An electrolyzer by employing the Co/Fe-MOF modified Ni foam as cathode and anode was assembled, which shows better performance and durability for overall water splitting than the system built from Pt/C and RuO2. This work offers thought for future in-depth digging of the potential of MOFs as electrocatalysts and expanding the family of MOFs electrocatalysts.

Tuning the electronic structures of catalysts with heteroatom-doped carbon materials promises advanced electrocatalytic performance, but challenge remains in the control of interface structures. Taking advantage of the highly tunable metal−organic framework (MOF) templates, NiSe2@N-doped carbon (NiSe2@NC) core-shell nano-octahedrons with well controlled interface structures were successfully synthesized and optimized for the hydrogen evolution reaction (HER). Selective selenization of mixed-linker Ni-MOFs allows the replacement of anionic carboxylate ligands by Se22− while trapping neutral N-coordinating ligands in NiSe2 nanocrystals. Further carbonization of N-ligands embedded NiSe2 nanocrystals resulted in NiSe2@NC core-shell nano-octahedrons covered by ultrathin N-doped carbon shells. The N-species was controlled by changing N-coordinating ligands in MOF precursors, resulting in an optimized HER catalyst with a small overpotential of 162 mV at 10 mA cm−2, and good long-term stability (up to 40 h) in 1.0 M KOH solution. A strong correlation between pyridinic-N and HER activity was experimentally defined and explained by DFT calculations.

Four metal–organic complexes [Ni(HET)(phen)(H2O)]·(HET)·H2O (1), [Cu(HET)(phen)(H2O)]·1.5H2O (2), [Cu2(HET)2(bipy)1.5(H2O)]·15DMF·2H2O (3), and [Cd2O(HET)2(bipy)(H2O)]·2H2O·EtOH (4) (HET = 1,4,5,6,7,7-hexachlorobicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid, phen = 1,10-phenanthroline, bipy = 4,4′-bipyridine) have been synthesized via hydro- or solvothermal reactions. It was found that complexes 1 and 2 are two-dimensional (2D) structures built from discrete complexes via the typical intermolecular interactions, and there was a closed loop built from the lattice water and carboxylate groups in 1 through intramolecular hydrogen bonds. Complex 3 exhibits three-dimensional (3D) structure with 5-connected bnn hexagonal BN topology. Complex 4 features a non-interpenetrating sql 2D coordination network, which is further linked into a 3D structure by C–H···Cl weak interaction. The properties of magnetism, fluorescence, and electrochemistry have also been investigated in this paper.

Mesoporous alumina with different morphologies was synthesized via thermal decomposition of the Al-based metal–organic frameworks (Al-MOFs) MIL-110 and MIL-100, in which Al-MOFs were used as the Al source and precursor. The hexagon rod-shaped and octahedron-shaped alumina products with morphology retained from their precursors were obtained and characterized. The results show that the construction of Al-MOFs, especially the aluminium building units plays a key role in the textural structure of the obtained alumina products. Besides, the differences in textural properties as well as the possible formation mechanism of the final alumina products are well explained by taking into account thermal behaviour and intrinsic structure features, especially the aluminium building units, of the Al-MOFs precursors. This work presents an easy new method to produce alumina with tailored morphology, tunable texture and microstructure, which is also an operational method fit for other metal oxide materials.

Three new metal–organic frameworks (MOFs) constructed from terphenyl-3,3′′,5,5′′-tetracarboxylic acid (H4ptptc) and zinc nitrate, [Zn2(ptptc)(DMF)3]·4H2O·5.5DMF (1), [Zn2(ptptc)(DMA)(H2O)]·2.5H2O·3.5DMA (2) and [Zn(ptptc)0.5(H2O)]·DMF·DMA (3), have been obtained and characterized. All the complexes exhibit 3D 4-connected networks with different topologies involving diamond (dia, for 1), lonsdaleite (lon, for 2) and Nbo (for 3), which emanate from the different reaction solvents (DMF, DMA and mixture of DMF/DMA (1 : 1), respectively). The results of photoluminescence properties show that the three complexes can be act as potential luminescent probes or sensors for detecting small organic molecules and toxic substances.

Hexagonal spindle-shaped mesoporous alumina with different internal structures were prepared using Al-based metal-organic frameworks MIL-96 as precursor through thermal treatment method. MIL-96 and alumina products were characterized by XRD, SEM, TEM, BET and TG. Results from these characterizations showed that alumina products keep the morphology of their precursor, and the thermal treatment conditions have large effect on alumina microstructures. The state of atmosphere and heating rate are the main factors affecting the internal textural properties of alumina. A possible transformation mechanism was also proposed. In addition, the effect of textural properties and structure on the adsorption ability of alumina was investigated. This work presents a novel method, which builds a direct linkage between MOF crystals and metal oxide microstructures, to control the morphology, structure and performance of alumina and other metal oxide materials.

Due to their tunable structure and porosity, metal–organic frameworks have provided a new platform for fluorescence sensing and adsorption/separation of gas or organic molecules. Many studies have focused on sensing metal ions, anions, or organic molecules through fluorescence quenching or enhancement of MOFs, but studies on pH-fluorescence sensors are seldom reported. Furthermore, highly solvent-dependent adsorption and degradation of dye molecules based on functional MOFs has not been explored to date. In this study, we describe a multifunctional Eu MOF, [H3O][Eu3(HBPTC)2(BPTC)(H2O)2]·4DMA (UPC-5, UPC = China University of Petroleum [East China]) based on a tetracarboxylate ligand. The luminescence intensity of UPC-5 is strongly correlated with the pH value in the pH range from 7.5 to 10.0, and a linear relationship between pH value and fluorescent intensity is observed. Another attractive property of UPC-5 is that its Li-exchanged form, Li-UPC-5, possesses solvent-dependent adsorption and degradation of rhodamine B. The highly efficient degradation or decolorization of rhodamine B with long-term stability and activity gives Li-UPC-5 a potential advantage in treating rhodamine B pollution.

Successful encapsulation of phosphotungstic acid (PTA) within the nanocages of MIL-101 has been achieved via “ bottle around ship ” approach under static condition. XRD, FT-IR, 31 P MAS NMR, N 2 adsorption, SEM–EDS and XRF confirm the incorporation and well-distribution of PTA in both middle and large cavities of the MIL-101. SEM, XRD and TEM reveal the dominant crystal shapes of high loading PTA@MIL-101 are a monolithic and the adjacent lattice planes of MIL-101 are larger due to the addition of PTA. The host–guest composite materials PTA@MIL-101 containing 17–50 wt.% of PTA have been obtained and demonstrate an excellent catalytic performance in the oxidative desulfurization process of the refractory sulfur-containing compounds. This is the first example of the application of MIL-101 or PTA@MIL-101 composite materials in oxidative desulfurization. The reactivity of the sulfur-containing compounds follows the order DBT > 4,6-DMDBT > BT. In four consecutive reaction cycles, the catalyst recovery is in excess of 71%, while the DBT conversion slightly decreases.

Two amino-functional copper metal-organic frameworks of formula [Cu3(ATTCA)2(H2O)3]·2DMF·11H2O·12EtOH (1) (H3ATTCA = 2-amino-[1,1:3,1-terphenyl]-4,4,5-tricarboxylic acid, pyz = pyrazine, DMF = dimethylformamide) and [Cu3(ATTCA)2(pyz)(H2O)]·2DMF·12H2O·8EtOH (2) were synthesized under solvothermal conditions and characterized by single-crystal X-ray diffraction, infrared spectroscopy, elemental analyses, thermogravimetric analyses, and powder X-ray diffraction. Single-crystal X-ray diffraction analysis revealed that both complexes 1 and 2 are built of the Cu2(COO)4 paddlewheel secondary building units with an fmj topology. Importantly, complex 1 can be transformed into complex 2 by the single-crystal to single-crystal transformation of which the coordinated water molecules are replaced with pyz molecules. However, the adsorption abilities of 2 are obviously lower than those of 1, as its pores are partially blocked by pyz molecules. Moreover, gas-adsorption analysis showed that the amino-functional 1 possesses higher gas-adsorption capacity than UMCM-151 for N2, H2, CH4, and C2H2, especially for CO2.

Hydrogen sulfide (H2S) has been considered as the third biologically gaseous messenger (gasotransmitter) after nitric oxide (NO) and carbon monoxide (CO). Fluorescent detection of H2S in living cells is very important to human health because it has been found that the abnormal levels of H2S in human body can cause Alzheimer’s disease, cancers and diabetes. Herein, we develop a cyclodextrin-based metal-organic nanotube, CD-MONT-2, possessing a {Pb14} metallamacrocycle for efficient detection of H2S. CD-MONT-2′ (the guest-free form of CD-MONT-2) exhibits turn-on detection of H2S with high selectivity and moderate sensitivity when the material was dissolved in DMSO solution. Significantly, CD-MONT-2′ can act as a fluorescent turn-on probe for highly selective detection of H2S in living cells. The sensing mechanism in the present work is based on the coordination of H2S as the auxochromic group to the central Pb(II) ion to enhance the fluorescence intensity, which is studied for the first time.

Crystallizations of tris(2-carboxyethyl)isocyanuric acid (H3tci) without or with N-heterocyclic organic molecules result in three distinct supramolecular complexes, [(H3tci)] (1), organic salt [(Hma)+·(H2tci)−] (2) and cocrystal [(H3tci)·(bipy)1.5] (3) (ma = melamine, bipy = 4,4′-bipyridine). In the absence of N-heterocyclic organic molecules, three 2-carboxyethyl arms of H3tci show a cisanti–cisanti–transanti conformation. The H3tci molecules are extended to a 2D 44-sql net via O–H⋯O hydrogen bonds. However, in the presence of ma or bipy, the conformation of the 2-carboxyethyl arms of H3tci in both 2 and 3 is transformed to cisanti–cisanti–cisgauche induced by cocrystallized N-heterocyclic organic molecules. In 2, ma plays a crucial role in the formation of O–H⋯N, N–H⋯O and O–H⋯O hydrogen bonds which direct the binary species to form the 2D double-layer structure containing 24-membered supramolecular macrocycles. Complex 3 is a 1D chain based on a [(H3tci)2·(bipy)2] 42-membered macrocycle incorporating the carboxyl–pyridyl H-bonding supramolecular synthons, which are extended by another bipy molecule to form the 1D chain. The 1D chains are further extended by means of a C–H⋯O non-classic hydrogen bond to form the resulting 2D layer containing three kinds of macrocycles. The 2D layers are packed into a 3D framework through π⋯π interaction between the triazinyl and pyridyl rings. Based on the structural analysis, we found that the conformation of H3tci could be modulated by introduction of the cocrystallized N-heterocyclic organic molecules. Moreover, the thermal stabilities of 2 and 3 are discussed.

Three lanthanide–organic frameworks have been solvothermally synthesized and characterized. Complex 1 {[Pr2(bbda)(OH)2(H2O)6]·12H2O}n (H4bbda = 5,5′-(2,4,6-trimethyl-1,3-phenylene)bis(methylene)bis(oxy)diisophthalic acid) is a 3D porous framework belonging to a 2-nodal net with the ssa topology. The coordinated formate ligand from in situ hydrolyzation of dmf binds metal centers to generate rigid rod-shaped SBUs (secondary building units) in both complexes 2 and 3, [Ln(HCOO)(L1)(dmf)]n (Ln = Er (2), Tm (3), H2L1 = 2,2′-(2,3,5,6-tetramethyl-1,4-phenylene) bis(methylene)bis(sulfanediyl)dibenzoic acid, dmf = N,N′-dimethylformamide). The flexible ligand H4bbda in complex 1 exhibits syn conformation, while the flexible ligand H2L1 in complexes 2 and 3 adopts anti conformation. The anti L1 ligand links the rod-shaped SBUs to give 2 and 3 3D network with the rtl topology.

A new 2D lanthanide-organic framework with 1D rod-shaped SBUs based on 4,6-dimethyl-5-nitroisophthalic acid has been solvothermally synthesized. The uncoordinated 4,4′-bipy ligands, which are trapped in the cavities by forming weak offset face-to-face pyridine–phenyl interaction with the wall of the cavities, play a template role in the formation of the 2D layer. To the best of our knowledge, this is the first 2D lanthanide-organic framework that synthesized by templated synthesis.

To assemble metal-organic supramolecules such as a metallamacrocycle and metal-organic coordination cage (MOCC), a series of flexible dicarboxylate ligands with the appropriate angle, 2,2'-(2,3,5,6-tetramethyl-1,4-phenylene)bis(methylene)bis(sulfanediyl)dibenzoic acid (H(2)L(1)), 2,2'-(2,5-dimethyl-1,4-phenylene)bis(methylene)bis(sulfanediyl)dibenzoic acid (H(2)L(2)), 2,2'-(2,4,6-trimethyl-1,3-phenylene)bis(methylene)bis(sulfanediyl)dinicotinic acid (H(2)L(3)), and 2,2'-(2,4,6-trimethyl-1,3-phenylene)bis(methylene)bis(sulfanediyl)dibenzoic acid (H(2)L(4)), have been designed and synthesized. Using these flexible ligands to assemble with metal ions, six metal-organic supramolecules, Cd(2)(L(1))(2)(dmf)(4)(H(2)O)(2).H(2)O (1), Mn(3)((1)L(2))(2)((2)L(2))(dmf)(2)(H(2)O)(2).5dmf (2), Cu(4)(L(3))(4)(H(2)O)(4).3dmf (3), Cu(4)(L(4))(4)(dmf)(2)(EtOH)(2).8dmf.6H(2)O (4), Mn(4)(L(4))(4)(dmf)(4)(H(2)O)(4).6dmf.H(2)O (5), and Mn(3)(L(4))(3)(dmf)(4).2dmf.3H(2)O (6), possessing a rectangular macrocycle, MOCCs or their extensions, and 1D or 2D coordination polymers, have been isolated. All complexes have been characterized by single-crystal X-ray diffraction, elemental analysis, and thermogravimetric analysis. Complex 1 is a discrete rectangular macrocycle, while complex 2 is a 2D macrocycle-based coordination polymer in which the L(2) ligand adopts both syn and anti conformations. Complexes 3-5 are discrete MOCCs in which two binuclear metal clusters are engaged by four organic ligands. The different geometries of the secondary building units (SBUs) and the axial coordinated solvates on the SBUs result in their different symmetries. Complex 6 is a 1D coordination polymer, extended from a MOCC made up of two metal ions and three L(4) ligands. All of the flexible dicarboxylate ligands adopt a syn conformation except that in complex 2, indicating that the syn conformational ligand is helpful for the formation of a metallamacrocycle and a MOCC. The magnetic properties of complexes 5 and 6 have also been studied.

The solvothermal reaction of Nd(NO3)3·6H2O and 5-amino-2,4,6-triiodoisophthalic acid (H2atiip) in DMF/ethonal/H2O (5:2:1) in the presence of pyridine gave rise to a new open neodymium−organic framework having the NbO structure type, [Nd(HCOO)(atiip)(DMF)2]·DMF·H2O (1). Complex 1 can keep its diffraction pattern even after being heated to 200 °C.

Three metal-organic frameworks with 1D zigzag chain [Zn(dte)(H2O)3]·2H2O (1), 2D double layer [Cd(dtb)(H2O)(phen)] (2), 3D network [Zn(dte)(phen)] (3) based on tetrazole-based ligands (H2dtb = 1,3-dis(2H-tetrazol-5-yl)benzene, H2dte = 1,4-ditetrazolylethylene, phen = 1,10-phenanthroline), have been synthesized and characterized. All the compounds exhibit unusual strong luminescence at room temperature in the solid state and can be potentially used as luminescent materials.

Using ligands BITMB and IPA or TMIPA (BITMB = 1,3-bis(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene, IPA = isophthalic acid, TMIPA = 2,4,6-trimethylisophthalic acid), in which the BITMB can adopt syn or anti conformations, three metal−organic frameworks (MOFs) have been synthesized. These MOFs contain a variety of structures: a one-dimensional (1D) chain (1), two-dimensional (2D) interpenetrating layer (2), and three-dimensional (3D) porous framework (3). In MOFs 1 and 2, the BITMB ligand adopts a syn conformation, connecting metal ions to form a macrometallocycle or chain as the subunit, which are further connected by the rigid carboxylate ligands to generate the final 1D chain or 2D interpenetrating layer. The BITMB ligand in 3 adopts an anti conformation, which connects metal ions to form a 1D zigzag chain as the subunit. The 1D chain subunits are further connected by the carboxylate ligand to form the 3D porous framework. The conformation of the BITMB and thus the dimensionality of the MOF can be contro...

Self-assembly of Zn(NO3)2·6H2O, 5-amino-2,4,6-triiodoisophthalic acid (H2atiip) and 4,4′-bipyridine (bpy) or 1,3-di(4-pyridyl)propane (dpp) gave rise to three unusual zinc metal–organic frameworks, Zn2(bpy)2(atiip)2·3H2O·2dmf (1), Zn8(dpp)8(atiip)8·4H2O (2), Zn(dpp)(atiip)·(dmf)·(H2O) (3). All complexes possess 2D layer frameworks constructed from 1D Zn-carboxylate tubular unit for 1, 1D Zn-carboxylate helical chain for 2 and 3. In 1 and 2, the bpy or dpp act as both bridging and blocking ligands and the blocking ligands play an important role in the formation of the 2D layer frameworks. Both 2 and 3 contain two different large metallomacrocycles. Photoluminescence measurements of 1–3 in the solid state at room temperature show that all complexes exhibit luminescence, which can be assigned to an intraligand π → π∗ transition or ligand-to-metal charge transfer (LMCT).

A three-dimensional porous Zn metal-organic framework (UPC-12) with high thermal and chemical stability was isolated in high yield and purity from a hydrothermal reaction. UPC-12 exhibits high selectivity for CO2 due to the formation of hydrogen bonds between CO2 molecules and the -COOH groups exposed inside the channels and the effective π-π interactions between CO2 molecules and the pillared bipyridine moieties of the MOF. The adsorption-desorption process was studied, for the first time, by both (13)C CP-TOSS NMR spectroscopy and in situ DRIFTS.

The self-assembly of flexible bended dicarboxylate ligand, 2,2′-(2,4,6-trimethyl-1,3-phenylene)bis(methylene)-bis(sulfanediyl)-dibenzoic acid (H2L), with Mn(OAc)2·4H2O resulted in the formation of a novel metal–organic coordination cage with binuclear manganese SBU as the vertex, which represents the first metal–organic coordination cage constructed from a flexible dicarboxylate ligand and a binuclear SBU.

By application of a newly developed C(3)-symmetric tripodal carboxylate ligand, 1,1',1''-(benzene-1,3,5-triyl)tripiperidine-4-carboxylic acid (H(3)BTPCA) to assemble with zinc ion in the presence of pyridine, a novel 2-fold interpenetrating polyhedral metal-organic framework with a primitive cubic network based on supermolecular building blocks (SBBs) has been synthesized. The basic paddlewheel secondary building units (SBUs) are connected by deprotonated BTPCA ligands to generate an octahedron as the SBB, which is further connected through the six vertexes by sharing the paddlewheel SBUs to give rise to the 3D primitive cubic network.

Two porous metal–organic frameworks (1 and 2) with a fsc topology based on mixed ligands have been assembled and characterized. The different pillared ligands (pyrazine for 1 and 4,4′-bipyridine for 2) significantly influence the pore size of the frameworks. Gas uptake measurements reveal that complex 1 possesses higher H2, CO2, and CH4 uptake capacities than 2, although the surface area of 1 is lower than that of complex 2. These results further experimentally prove that the pore size plays an important role in gas uptake in porous MOFs, and the slit pore with a size of ~6 Å exhibits stronger interactions with gas molecules.

Three flexible bent dicarboxylate ligands, 2,2′-(2,3,5,6-tetramethyl-1,4-phenylene)bis(methylene)bis(sulfanediyl)dibenzoic acid (H2L1), 2,2′-(1,4-phenylenebis(methylene))bis(sulfanediyl)dibenzoic acid (H2L9) and 2,2′-(2,3,5,6-tetramethyl-1,4-phenylene)bis(methylene)bis(oxy)dibenzoic acid (H2L10), have been designed and synthesized. The positions of the functional substituents are in 1,4-positions of the central benzene ring, and all the ligands can adopt syn and anti conformations. By applying these flexible ligands to assemble with thulium ions or zinc ions, three metal–organic supramolecules with metallamacrocycles or 1D chains have been isolated. L1 adopts a syn conformation in complex 1, leading to a 0D metallamacrocycle, L9 in complex 2 adopts an anti conformation to form a 1D “rainbow-like” chain while L10 in complex 3 adopts both syn and anti conformations. L10 in a syn conformation connects Zn4(OH)2(CO2)4 SBU to form a 0D metallamacrocycle, which is further connected by the ligand in an anti conformation to generate a 1D coordination polymer.

Biphasic solvothermal reaction of Cu(NO3)2·6H2O and 2,3,5,6-tetramethyl-1,4-benzenedicarboxylic acid (H2TBDC) resulted in the formation of a novel coordination polymer, [Cu(TBDC)1/2]·H2O (BPS-1). BPS-1 possesses a 3D framework containing 1D Cu(I)–COO helical chains. The use of an organic solvent with a high boiling point and an extension of the reaction time play important roles in the reduction of Cu(II) ions to Cu(I) ions and the formation of BPS-1.

Three flexible dicarboxylate ligands 2,2′-(1,2-phenylenebis(methylene))bis(sulfanediyl)dibenzoic acid (H2L6), 2,2′-(2,4,6-trimethyl-1,3-phenylene)bis(methylene)bis(oxy)dibenzoic acid (H2L7) and 2,2′-(1,4-phenylenebis(methylene))bis-(sulfanediyl)dinicotinic acid (H2L8), have been designed and synthesized. All ligands can adopt syn or anti conformations and the positions of the functional substituents in the central benzene ring change gradually from 1,2-, 1,3- to 1,4-position. By applying these flexible ligands to assemble with copper ions, four metal–organic complexes based on paddlewheel SBU have been isolated. Complexes 1 and 2 are discrete molecular chairs. Complex 3 is a 1D molecular-chair-based coordination polymer. The molecular chairs, similar to that found in 1 and 2, are infinitely connected by the bridging 4,4′-bipy ligands to result in the formation of the 1D chain structure. Complex 4 is a two-dimensional wavelike layer structure containing a 68-member ring. Both L6 and L7 in 1 and 2 adopt syn conformation, while L8 adopts anti conformation, which results in the formation of the 2D layer structure of complex 4.