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Covalent organic frameworks (COFs) are an emerging crystalline polymer that is constructed by the organic blocks through reversible polymerization. In this review, we have summarized the strategies for designing covalent organic frameworks for the oxygen reduction reaction. The discussion involved the new structural design of COFs and modifications fitting to the applications. Active sites manipulated scale from the single atom's electron states to the body framework arrangements. This review has anticipated the researchers to enlighten new ORR catalyst designing and optimization. [ABSTRACT FROM AUTHOR]

Photocatalytic oxygen reduction reactions and water oxidation reactions are extremely promising green approaches for massive H2O2 production. Nonetheless, constructing effective photocatalysts for H2O2 generation is critical and still challenging. Since the network topology has significant impacts on the electronic properties of two dimensional (2D) polymers, herein, for the first time, we regulated the H2O2 photosynthetic activity of 2D covalent organic frameworks (COFs) by topology. Through designing the linking sites of the monomers, we synthesized a pair of novel COFs with similar chemical components on the backbones but distinct topologies. Without sacrificial agents, TBD‐COF with cpt topology exhibited superior H2O2 photoproduction performance (6085 and 5448 μmol g−1 h−1 in O2 and air) than TBC‐COF with hcb topology through the O2‐O2⋅−‐H2O2, O2‐O2⋅−‐O21‐H2O2, and H2O‐H2O2 three paths. Further experimental and theoretical investigations confirmed that during the H2O2 photosynthetic process, the charge carrier separation efficiency, O2⋅− generation and conversion, and the energy barrier of the rate determination steps in the three channels, related to the formation of *OOH, *O21, and *OH, can be well tuned by the topology of COFs. The current study enlightens the fabrication of high‐performance photocatalysts for H2O2 production by topological structure modulation. [ABSTRACT FROM AUTHOR]

The ion extraction and electro/photo catalysis are promising methods to address environmental and energy issues. Covalent organic frameworks (COFs) are a class of promising template to construct absorbents and catalysts because of their stable frameworks, high surface areas, controllable pore environments, and well‐defined catalytic sites. Among them, ionic COFs as unique class of crystalline porous materials, with charges in the frameworks or along the pore walls, have shown different properties and resulting performance in these applications with those from charge‐neutral COFs. In this review, current research progress based on the ionic COFs for ion extraction and energy conversion, including cationic/anionic materials and electro/photo catalysis is reviewed in terms of the synthesis strategy, modification methods, mechanisms of adsorption and catalysis, as well as applications. Finally, we demonstrated the current challenges and future development of ionic COFs in design strategies and applications. [ABSTRACT FROM AUTHOR]

The catalytic performance for electrocatalytic CO2 reduction reaction (CO2RR) depends on the binding strength of the reactants and intermediates. Covalent organic frameworks (COFs) have been adopted to catalyze CO2RR, and their binding abilities are tuned via constructing donor‐acceptor (DA) systems. However, most DA COFs have single donor and acceptor units, which caused wide‐range but lacking accuracy in modulating the binding strength of intermediates. More elaborate regulation of the interactions with intermediates are necessary and challenge to construct high‐efficiency catalysts. Herein, the three‐component COF with D‐A‐A units was first constructed by introducing electron‐rich diarylamine unit, electron‐deficient benzothiazole and Co‐porphyrin units. Compared with two‐component COFs, the designed COF exhibit elevated electronic conductivity, enhanced reducibility, high efficiency charge transfer, further improving the electrocatalytic CO2RR performance with the faradic efficiency of 97.2 % at −0.8 V and high activity with the partial current density of 27.85 mA cm−2 at −1.0 V which exceed other two‐component COFs. Theoretical calculations demonstrate that catalytic sites in three‐component COF have suitable binding ability of the intermediates, which are benefit for formation of *COOH and desorption of *CO. This work offers valuable insights for the advancement of multi‐component COFs, enabling modulated charge transfer to improve the CO2RR activity. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) have been utilized as the ideal candidates to preciously construct electrocatalysts. However, the highly ordered degree of COFs renders the catalytic centers closely stacked, which limits the utilization efficiency of catalytic sites. Herein, we have first constructed dangling and staggered‐stacking aldehyde (–CHO) from [4 + 3] COFs as catalytic centers for 2e− oxygen reduction reaction (ORR). The new catalytic COFs have unreacted dangling ‐CHO out of the COFs' planes, which are more easily exposed in electrolytes than the sites in the frameworks. More importantly, these –CHO adopt staggered stacking models, and thus provide larger space for mass transport than those with eclipsed stacking models. In addition, by tuning the triratopic linkers in the COFs, the catalytic properties are well modulated. The optimized COF shows high selectivity and activity for 2e− ORR, with H2O2 selectivity of 91%, and mass activity of 12.2 A g−1, respectively. The theoretical calculation further reveals the higher activity for the pyridine‐contained B18C6‐PTTA‐COF due to the promoted binding ability of the intermediate OOH* at the carbon in dangling –CHO. This work provides us with a new insight into designing electrocatalysts based on COFs. [ABSTRACT FROM AUTHOR]

Binding water molecules to polar sites in covalent organic frameworks (COFs) is inevitable, but the corresponding solvent effects in electrocatalytic process have been largely overlooked. Herein, we investigate the solvent effects on COFs for catalyzing the oxygen reduction reaction (ORR). Our designed COFs incorporated different kinds of nitrogen atoms (imine N, pyridine N, and phenazine N), enabling tunable interactions with water molecules. These interactions play a crucial role in modulating electronic states and altering the catalytic centers within the COFs. Among the synthesized COFs, the one with pyridine N atoms exhibits the highest activity, with characterized by a half‐wave potential of 0.78 V and a mass activity of 0.32 A mg−1, which surpass those from other metal‐free COFs. Theoretical calculations further reveal that the enhanced activity can be attributed to the stronger binding ability of *OOH intermediates to the carbon atoms adjacent to the pyridine N sites. This work sheds light on the significance of considering solvent effects on COFs in electrocatalytic systems, providing valuable insights into their design and optimization for improved performance. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) have been utilized for catalyzing the reduction of carbon dioxide (CO2RR) due to their atomic metal centers and controllable pore channels, which are facilitated by different covalent bonds. However, the exploration of boron‐based linkages in these catalytic COFs has been limited owing to potential instability. Herein, we present the construction of boronic ester‐linked COFs through nucleophilic substitution reactions in order to catalyze the CO2RR. The inclusion of abundant fluorine atoms within the frameworks enhances their hydrophobicity and subsequently improves water tolerance and chemical stability of COFs. The content of boron atoms in the COF linkages was carefully controlled, with COFs featuring a higher density of boron atoms exhibiting increased electronic conductivity, enhanced reductive ability, and stronger binding affinity towards CO2. Consequently, these COFs demonstrate improved activity and selectivity. The optimized COFs achieve the highest activity, achieving a turnover frequency of 1695.3 h−1 and a CO selectivity of 95.0 % at −0.9 V. Operando synchrotron radiation measurements confirm the stability of Co (II) atoms as catalytically active sites. By successfully constructing boronic ester‐linked COFs, we not only address potential instability concerns but also achieve exceptional catalytic performance for CO2RR. [ABSTRACT FROM AUTHOR]

The oxygen reduction reaction (ORR) is the key reaction in metal air and fuel cells. Among the catalysts that promote ORR, carbon‐based metal‐free catalysts are getting more attention because of their maximum atom utilization, effective active sites and satisfactory catalytic activity and stability. However, the pyrolysis synthesis of these carbons resulted in disordered porosities and uncontrolled catalytic sites, which hindered us in realizing the catalysts' design, the optimization of catalyst performance and the elucidation of structure–property relationship at the molecular level. Covalent organic frameworks (COFs) constructed with designable building blocks have been employed as metal‐free electrocatalysts for the ORR due to their controlled skeletons, tailored pores size and environments, as well as well‐defined location and kinds of catalytic sites. In this Concept article, the development of metal‐free COFs for the ORR is summarized, and different strategies including skeletons regulation, linkages engineering and edge‐sites modulation to improve the catalytic selectivity and activity are discussed. Furthermore, this Concept provides prospectives for designing and constructing powerful electrocatalysts based on the catalytic COFs. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) have attracted considerable attention as adsorbents for capturing and separating gold from electronic wastes. To enhance the binding capture efficiency, constructing hydrogen‐bond nanotraps along the pore walls was one of the most widely adopted approaches. However, the development of absorbing skeletons was ignored due to the weak binding ability of the gold salts (Au). Herein, we demonstrated skeleton engineering to construct highly efficiently absorbs for Au capture. The strong electronic donating feature of diarylamine units enhanced the electronic density of binding sites (imine‐linkage) and thus resulted in high capacities over 1750 mg g−1 for all three COFs. Moreover, the absorbing performance was further improved via the ionization of diarylamine units. The ionic COF achieved 90 % of the maximal adsorption capacity, 1.63 times of that from the charge‐neutral COF within ten minutes, and showed remarkable uptakes of 1834 mg g−1, exceptional selectivity (97.45 %) and cycling stability. The theoretical calculation revealed the binding sites altering from imine bonds to ionic amine sites after ionization of the frameworks, which enabled to bind the AuCl4− via coulomb force and contributed to enhanced absorbing kinetics. This work inspires us to design molecular/ionic capture based on COFs. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) have been developed as the precursors to construct porous carbons for electrocatalytic systems. However, the influences of carbon dimensions on the catalytic performance are still underexplored. In this work, we have first constructed COF‐derived carbons by template‐synthesis strategy in different dimensions to catalyze the carbon dioxide reduction (CO2RR). By using different templates, the one‐dimensional (1D), two‐dimensional (2D), and three‐dimensional (3D) COF‐derived carbons have been employed to anchor Co‐porphyrin to form the Co‐N5 sites to catalyze CO2RR. The 1D catalyst templated by carbon nano tubes presents high binding ability of CO2, more defective sites, and higher electronic conductivity, resulting in a higher catalytic activity for CO2 and selectivity of CO than 2D and 3D carbon‐based catalysts. The 1D catalyst delivers the turnover frequency values of 1150 h−1 and the FECO of 94.5% at 0.7 V versus RHE, which is significantly better than those of 2D and 3D carbon‐based catalysts. [ABSTRACT FROM AUTHOR]

The 3D covalent organic frameworks (COFs) have attracted considerable attention owing to their unique structural characteristics. However, most of 3D COFs have interpenetration phenomena, which will result in decreased surface area and porosities, and thus limited their applications in molecular/gas capture. Developing 3D COFs with non‐fold interpenetration is challenging but significant because of the existence of non‐covalent interactions between the adjacent nets. Herein, a new 3D COF (BMTA‐TFPM‐COF) with dia topology and non‐fold interpenetration for Au ion capture is first demonstrated. The constructed COF exhibits a high Brunauer–Emmett–Teller surface area of 1924 m2 g−1, with the pore volume of 1.85 cm3 g−1. The high surface area and abundant cavities as well as the abundant exposed CN linkages due to the non‐interpenetration enable to absorb Au3+ with high capacity (570.18 mg g−1), selectivity (99.5%), and efficiency (68.3% adsorption of maximum capacity in 5 min). This work provides a new strategy to design 3D COFs for ion capture. [ABSTRACT FROM AUTHOR]

Metal‐free covalent organic frameworks (COFs) have been employed to catalyze the oxygen reduction reaction (ORR). To achieve high activity and selectivity, various building blocks containing heteroatoms and groups linked by imine bonds were used to create catalytic COFs. However, the roles of linkages of COFs in ORR have not been investigated. In this work, the catalytic linkage engineering has been employed to modulate the catalytic behaviors. To create single catalytic sites while avoiding other possible catalytic sites, we synthesized COFs from benzene units linked by various bonds, such as imine, amide, azine, and oxazole bonds. Among these COFs, the oxazole‐linkage in COFs enables to catalyze the ORR with the highest activity, which achieved a half‐wave potential of 0.75 V and a limited current density of 5.5 mA cm−2. Moreover, the oxazole‐linked COF achieved a conversion frequency (TOF) value of 0.0133 S−1, which were 1.9, 1.3, and 7.4‐times that of azine‐, amide‐ and imine‐COFs, respectively. The theoretical calculation showed that the carbon atoms in oxazole linkages facilitated the formation of OOH* and promoted protonation of O* to form the OH*, thus advancing the catalytic activity. This work guides us on which linkages in COFs are suitable for ORR. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks and covalent organic frameworks have been widely employed in electrochemical catalysis owing to their designable skeletons, controllable porosities, and well‐defined catalytic centers. However, the poor chemical stability and low electron conductivity limited their activity, and single‐functional sites in these frameworks hindered them to show multifunctional roles in catalytic systems. Herein, we have constructed novel metal organic polymers (Co‐HAT‐CN and Ni‐HAT‐CN) with dual catalytic centers (metal–N4 and metal–N2) to catalyze oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). By using different metal centers, the catalytic activity and selectivity were well‐tuned. Among them, Co‐HAT‐CN catalyzed the ORR in a 4e− pathway, with a half‐wave potential of 0.8 V versus RHE, while the Ni‐HAT‐CN catalyze ORR in a 2e− pathway with H2O2 selectivity over 90%. Moreover, the Co‐HAT‐CN delivered an overpotential of 350 mV at 10 mA cm−2 with a corresponding Tafel slope of 24 mV dec−1 for OER in a 1.0 M KOH aqueous solution. The experimental results revealed that the activities toward ORR were due to the M–N4 sites in the frameworks, and both M–N4 and M–N2 sites contributed to the OER. This work gives us a new platform to construct bifunctional catalysts. [ABSTRACT FROM AUTHOR]

Two‐dimensional covalent organic frameworks (2D COFs) are often employed for electrocatalytic systems because of their structural diversity. However, the efficiency of atom utilization is still in need of improvement, because the catalytic centers are located in the basal layers and it is difficult for the electrolytes to access them. Herein, we demonstrate the use of 1D COFs for the 2e− oxygen reduction reaction (ORR). The use of different four‐connectivity blocks resulted in the prepared 1D COFs displaying good crystallinity, high surface areas, and excellent chemical stability. The more exposed catalytic sites resulted in the 1D COFs showing large electrochemically active surface areas, 4.8‐fold of that of a control 2D COF, and thus enabled catalysis of the ORR with a higher H2O2 selectivity of 85.8 % and activity, with a TOF value of 0.051 s−1 at 0.2 V, than a 2D COF (72.9 % and 0.032 s−1). This work paves the way for the development of COFs with low dimensions for electrocatalysis. [ABSTRACT FROM AUTHOR]

Construction of catalytic covalent organic frameworks (COFs) for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is significant but rarely demonstrated. In this work, we have first constructed bifunctional COFs towards ORR and OER by integrating diarylamine derivatives into the Co‐porphyrin based frameworks. Both of the new COFs (CoTAPP‐PATA‐COF and CoTAPP‐BDTA‐COF) have good ordered structures, high surface areas, and robust chemical stability. The diarylamine units, as a typical electron donor and redox‐active cores, promote intramolecular electron transport along the frameworks and improve the electrochemically active surface areas. Thus, the COFs showed higher catalytic activities than that of the COF without redox‐active units. CoTAPP‐PATA‐COF had a halfwave potential of 0.80 V towards ORR, and delieved an overpotential of 420 mV for OER in 0.1 M KOH. The theoretical calculation revealed introducing diarylamine unites improved the oxygen electrocatalysis. [ABSTRACT FROM AUTHOR]

Despite rapid progress over the past decade, most polycondensation systems even upon a small structural variation of the building units eventually result in amorphous polymers other than the desired crystalline covalent organic frameworks. This synthetic dilemma is a central and challenging issue of the field. Here we report a novel approach based on module‐patterned polymerization to enable efficient and designed synthesis of crystalline porous polymeric frameworks. This strategy features a wide applicability to allow the use of various knots of different structures, enables polycondensation with diverse linkers, and develops a diversity of novel crystalline 2D polymers and frameworks, as demonstrated by using the C=C bond‐formation polycondensation reaction. The new sp2‐carbon frameworks are highly emissive and enable up‐conversion luminescence, offer low band gap semiconductors with tunable band structures, and achieve ultrahigh charge mobilities close to theoretically predicted maxima. [ABSTRACT FROM AUTHOR]

Crown ethers are a class of macrocyclic molecules with unique flexible structures but they are rarely integrated in covalent organic frameworks (COFs). To date, employing flexible organic units such as crown ethers to construct COFs with high crystallinity and surface area are still a challenge. In this work, two new COFs with different flexible crown ethers as backbone rather than side chains are synthesized and further employed for alkali metal ions separation. Both of COFs possess high surface areas, good crystallinity, and excellent chemical stability. Interestingly, these two new COFs with 18‐crown‐6 or 24‐crown‐8 units showed remarkable binding ability of K+ or Cs+ owing to the size‐fit effect. This work demonstrated that the unique structural features of crown ethers will lead to increase interest in fabricating COFs with crown ethers. [ABSTRACT FROM AUTHOR]

Electrochemical synthesis of H2O2 with high productivity is a significant challenge in electrocatalysis. Herein, we develop Mg‐ion contained covalent organic frameworks (MgP‐DHTA‐COF), comprising stacked 2D layers, well‐defined skeletons, and well‐ordered monodispersed active sites, for the electrocatalytic production of H2O2 directly from O2 and H2O. The precise‐designed MgP‐DHTA‐COF achieves H2O2 selectivity up to 96%, high Faradaic efficiency of 91% and reliable stability for H2O2 synthesis in 0.10 mol L−1 KOH aqueous solution. Both experiments and simulations demonstrate that the pyrrolic‐N fixed Mg ions in the knots promote the reactivity of COF and enhance the adsorption ability of OOH*. This work provides a valuable example for the design of an efficient electrocatalyst based on COFs for H2O2 production. [ABSTRACT FROM AUTHOR]

Developing bifunctional electrocatalysts with high activity toward the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) is of great significance for metal–air batteries. Herein, a covalent organic framework (COF)‐derived bifunctional electrocatalyst toward the ORR and the OER is demonstrated, in which the COF‐derived carbon on carbon nanotubes is used as the support to anchor active bimetal Ni/Fe clusters and nanoparticles. Since Ni/Fe ions are immobilized in the pore channels of the COFs, the aggregation and migration of ions under pyrolysis are effectively hindered. In addition, the COF‐derived carbon‐made catalyst features abundant nitrogen content and a high mesoporous volume. As a result, the catalyst displays ultrahigh ORR activity, with a half‐wave potential of 0.87 V versus reversible hydrogen electrode in 0.1 m KOH electrolyte. Moreover, the catalyst achieves a low operating potential of 1.55 V at a current density of 10 mA cm−2, with a Tafel slop of 61 mV decade−1 for OER in 0.1 m KOH, superior to most oxygen electrocatalysts. Furthermore, the catalyst also exhibits remarkable performance in Zn–air batteries. This work demonstrates a new insight into developing bifunctional catalysts from COFs. [ABSTRACT FROM AUTHOR]

A strategy based on covalent organic frameworks for ultrafast ion transport involves designing an ionic interface to mediate ion motion. Electrolyte chains were integrated onto the walls of one‐dimensional channels to construct ionic frameworks via pore surface engineering, so that the ionic interface can be systematically tuned at the desired composition and density. This strategy enables a quantitative correlation between interface and ion transport and unveils a full picture of managing ionic interface to achieve high‐rate ion transport. Moreover, the effect of interfaces was scaled on ion transport; ion mobility is increased in an exponential mode with the ionic interface. This strategy not only sets a benchmark system but also offers a general guidance for designing ionic interface that is key to systems for energy conversion and storage. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) are a new class of crystalline porous polymers comprised mainly of carbon atoms, and are versatile for the integration of heteroatoms such as B, O, and N into the skeletons. The designable structure and abundant composition render COFs useful as precursors for heteroatom‐doped porous carbons for energy storage and conversion. Herein, we describe a multifunctional electrochemical catalyst obtained through pyrolysis of a bimetallic COF. The catalyst possesses hierarchical pores and abundant iron and cobalt nanoparticles embedded with standing carbon layers. By integrating these features, the catalyst exhibits excellent electrochemical catalytic activity in the oxygen reduction reaction (ORR), with a 50 mV positive half‐wave potential, a higher limited diffusion current density, and a much smaller Tafel slope than a Pt‐C catalyst. Moreover, the catalyst displays superior electrochemical performance toward the hydrogen evolution reaction (HER), with overpotentials of −0.26 V and −0.33 V in acidic and alkaline aqueous solution, respectively, at a current density of 10 mA cm−2. The overpotential in the catalysis of the oxygen evolution reaction (OER) was 1.59 V at the same current density. Bimetallic electrocatalyst: A bimetallic electrochemical catalyst from a covalent organic framework is reported. The catalyst has a hierarchical pore structure and abundant FeCo alloy nanoparticles embedded with standing carbon layers. By integrating these features, the catalyst exhibits excellent multifunctional electrochemical catalytic activity toward the oxygen reduction reaction, oxygen evolution reaction, and hydrogen evolution reaction. [ABSTRACT FROM AUTHOR]

Lithium (Li) metal batteries with remarkable energy densities are restrained by short lifetime and low Coulombic efficiency (CE), resulting from the accumulative Li dendrites and dead Li during cycling. Here, we prepared a new three‐dimensional (3D) covalent organic framework (COF) with dense lithiophilic sites (heteoatom weight contents of 32.32 wt %) as an anodic protective layer of Li metal batteries. The 3D COF was synthesized using a [6+4] synthesis strategy by inducing flexible 6‐connected cyclotriphosphazene derivative aldehyde and 4‐connected porphyrin‐based tetraphenylamines. Both phosphazene and porphyrin rings in the COF served as electron‐rich and lithiophilic sites, enhancing a homogeneous Li+ flux via 3D direction towards highly smooth and compact Li deposition. The Li/Por‐PN‐COF‐Cu cells achieved a record average CE of 99.1 % for 320 cycles with smooth Li deposition. Meanwhile, the abundant lithiophilic sites can promote fast Li+ transport with Li+ transference number of 0.87, enabling LiFePO4 full cell with stable stripping/plating processes even at a harsh rate of 5 C. Theoretical calculations revealed that the strong interaction force between Li+ and the COF facilitated the dissolution of Li+ from the electrolyte, and the low migration barrier of 1.08 eV indicated a favorable interaction between the Li+ ions and the π‐electron system. [ABSTRACT FROM AUTHOR]

Solar‐driven H2O2 production via the oxygen reduction reaction (ORR) and water oxidation reaction (WOR) dual channels is green and sustainable but severely restricted by the sluggish reaction kinetics. Constructing intriguing photocatalysts with effective active centers is a shortcut to breaking the kinetic bottleneck with great significance. Herein, we synthesize two novel neutral phenanthridine‐based covalent organic frameworks (PD‐COF1 and PD‐COF2) for photosynthesizing H2O2. Compared to the no phenanthridine counterpart (AN‐COF), the H2O2 photosynthetic activities of PD‐COF1 and PD‐COF2 are markedly boosted. In air and pure water without sacrificial agents, under Xe lamp and natural sunlight, the H2O2 photogeneration rate of PD‐COF2 is 6103 and 3646 μmol g−1 h−1, respectively. Further experimental and theoretical inspections demonstrate that introducing phenanthridine units into COFs smoothly modulates the charge carrier dynamics and thermodynamically favors the generation of crucial OOH* and OH* intermediates in the ORR and WOR paths, respectively. Additionally, this is the first time the neutral phenanthridine moiety serves as the photooxidation unit for 2e− WOR towards H2O2 photoproduction. The current work sheds light on exploring novel catalytic centers for high‐performance H2O2 evolution. [ABSTRACT FROM AUTHOR]

Metal‐free covalent organic frameworks (COFs) are employed in oxygen reduction reactions (ORR) because of their diverse structural units and controllable catalytic sites, and the edge sites have high catalytic activity than the basal sites. However, it is still challenge to modulate the edge sites in COFs, because the extended frameworks in two‐ or three‐dimensional topologies resulted in limited edge parts. In this study, we have demonstrated the edge site modulation engineering based on one dimensional (1D) COFs to catalyze the ORR, which featured distinct edge groups‐carbonyl, diaminopyrazine, phenylimidazole, and benzaldehyde imidazole units. The synthesized COFs have same ordered frameworks, similar pore structure, but had different electronic states of the carbons along the edge sites, which results in tailored catalytic properties. Notably, the COF functionalized with a phenylimidazole edge group exhibited superior catalytic performance compared to the other synthesized COFs. And the theoretical calculation further revealed the different edge sites had tunable binding ability of the intermediates OOH*, which contributed modulated activity. Our findings introduce a novel way for designing COFs optimized for ORR applications through molecular level control of edge sites. [ABSTRACT FROM AUTHOR]

Producing hydrogen by electrolyzing water has received increased attention. Nevertheless, a major challenge remains in the search for high performance hydrogen evolution reaction (HER) electrocatalysts. In this work, multi-walled carbon nanotubes (MWCNTs) capped by TpPa covalent organic framework (TpPa-COF) react with cobalt nitrate hexahydrate (Co(NO 3) 2 ·6H 2 O) to form a novel ternary one-body complex (MWCNTs@TpPa-COF@Co/CoO). Wherein, TpPa-COF is constructed from 2,4,6-Triformylphloroglucinol (Tp) and p -phenylenediamine (Pa) as structural units. This COF is relatively inexpensive, provides more coordination sites for metal loading, and is particularly stable in acidic and basic media. The results show that the composite material has high electrocatalytic HER activity in a potassium hydroxide (KOH) condition with an overpotential value of 28.8 mV and a Tafel slope of 69.07 mV dec−1 at a current density of 10 mA cm−2. Meanwhile, the MWCNTs@TpPa-COF@Co/CoO showed excellent stability after 2000 cycles in alkaline media. The characterization demonstrated that the material provided low resistance during the charge transfer process, which resulted in improved electrochemical performance. In addition, the COF loaded with cobalt nanoparticles provided more active sites for the reaction. Thus, the synthesized MWCNTs@TpPa-COF@Co/CoO emerges turns out to be a Pt-free, stable and efficient HER electrocatalyst, holding significant promise for practical applications. • MWCNTs@TpPa-COF@Co/CoO electrocatalyst with high HER performance has been prepared. • The accessible active sites on MWCNTs and COF contribute to the electrocatalytic HER performance. • The best electrocatalyst exhibited an ultra-low overpotential of 28.8 mV@10 m A/cm2. • The composite shows remarkable long-term stability after 24 h and 2000 CV cycles. [ABSTRACT FROM AUTHOR]

• The atomic CoN 2 O 2 sites have been first constructed for CO 2 RR via template pyrolysis of COFs. • The catalyst had abundant CoN 2 O 2 sites with a Co content of 4.27 wt%. • The catalyst showed a remarkable catalytic activity and selectivity towards CO 2 RR. Electrocatalytic CO 2 reduction (CO 2 RR) is critical in addressing CO 2 emissions. Single atom catalysts, are attracting considerable attention for CO 2 RR because of their high atom utilization efficiencies and tailored electron states. However, the catalytic sites remain limited and developing novel catalytic centers is a significant and challenge. Herein, for the first time, we fabricated CoN 2 O 2 sites in 2D carbon for use in CO 2 RR via template pyrolysis of covalent organic frameworks (COFs). After forming the COF on the surface of Mg/Al-LDH, the obtained catalyst displayed a layered morphology with a thickness of approximately 36 nm and had abundant CoN 2 O 2 sites (4.27 wt% Co). The catalyst showed a remarkable catalytic activity towards CO 2 RR, with Faradaic efficiencies of 80.2–96.5 % at applied potentials between −0.6 and −1.0 V. Theoretical calculations showed that the CoN 2 O 2 sites favor the stretching and cleavage of COOH* at the Co active centers, accelerating the rate-determining step of COOH* formation. [ABSTRACT FROM AUTHOR]

• We have first constructed catalytic COFs for formic acid synthesis via CO 2 RR, and the electronic states of porphyrin-Cu(II) sites were well tuned by using different electronic densities of linkers. • The flowed electrons from electron-rich dithiophene to the Cu2+ promoted the electron transferring along the frameworks, and contributed to high electronic conductivity and reductive ability. • The targeted COF showed higher activity with a turnover of frequency (TOF) value of 486.2 h−1, and selectivity with faradic efficiencies (FE) for HCOOH of 84 %, which were 3.9 and 2.3 times of those from the controlled COF with electron-drawing linkers. Covalent organic frameworks (COFs) have been well developed to construct electrocatalysts for CO 2 reduction (CO 2 RR) towards CO. However, how to synthesize liquid products is still a challenge due to the lack of suitable catalytic centers. Herein, we have first achieved catalytic COF for highly efficient formate synthesis via CO 2 RR by modulating the electronic states of CuN4 sites. The flowed electrons from electron-rich dithiophene linker to the Cu2+ promoted the electron transferring along the frameworks, contributed to high electronic conductivity and reductive ability. The designed catalyst showed higher activity with a turnover of frequency value of 486.2 h−1, and selectivity with faradic efficiencies for HCOOH of 84%. The theoretical calculation and the in-situ synchrotron radiation Fourier transform infrared (SR-FTIR) spectroscopy measurements revealed that dithiophene made catalytic centers easily formed the intermediate OCOH* and suppressing the competing intermediate H*, thus enhancing the activity and selectivity in the carbon dioxide reduction. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) with bioinspired N,S-sites were constructed. Single Co atoms were coordinated with N,S-sites to create Co-THD-COF, which photocatalyzed CO 2 conversion to CO with 95.1 % selectivity in water and natural seawater. The synergistic interaction between THD-COF and the single atomic Co center enhanced CO 2 adsorption, activation, and reduced reaction energy barriers for *COOH intermediates, resulting in good performance. [Display omitted] • Learning from natural carbon monoxide dehydrogenase, we delicately designed a THD-COF with bioinspired N,S-coordination sites and constructed Co-THD-COF by anchoring single Co atoms on the N,S-sites. • Co-THD-COF can photocatalyze CO 2 conversion to CO with 95.1 % selectivity in water and natural seawater with reusability. • Under visible light, Co-THD-COF displayed dramatically enhanced photocatalytic CO 2 RR activity, exhibiting the CO generating rate of 9357 μmol g−1h−1. • The synergistic interaction between THD-COF and the single atomic Co center enhanced CO 2 adsorption, activation, and reduced reaction energy barriers for *COOH intermediates, resulting in good performance. Photocatalytic CO 2 reduction reaction (CO 2 RR) has promising potential to address global energy and environmental challenges but is severely limited by sluggish kinetics and poor selectivity, where the chemical microenvironments and electronic structures of the catalytic center play pivotal roles. Herein, inspired by carbon monoxide dehydrogenase, which can accelerate CO 2 to CO reduction, we delicately design a covalent organic framework (THD-COF) with bioinspired N,S-coordination sites from thiophene and imine modules on the skeleton and construct Co-THD-COF by anchoring single Co atoms on the N,S-sites. Under visible light, employing binary mixed sacrificial agents, with the help of photosensitizer [Ru(bpy) 3 ]Cl 2 ·6H 2 O, Co-THD-COF displays dramatically enhanced photocatalytic CO 2 RR activity, exhibiting an astounding CO generating rate of 9357 μmol g−1h−1 with the selectivity of 95.1 %. Additionally, Co-THD-COF can photocatalyze CO 2 conversion smoothly in real seawater without loss of CO selectivity. Experimental and computational analysis further manifest that the single Co atom is the catalytic active center. Co-THD-COF significantly promotes CO 2 adsorption and activation, charge separation dynamics, and is also beneficial to the formation of the crucial *COOH intermediates. The current study offers deep insights into the effective conversion of CO 2 and enlightens the design of novel bioinspired coordination sites for single-atom photocatalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • The ladder covalent organic frameworks showed high electrocatalytic performance. • The ladder π-conjugation contributed to electronic conductivity. • The natural phenolic molecule improved CO 2 uptakes and reductive capacity. • The theoretical calculation revealed the phenolic molecule enhance the activity. Covalent organic frameworks (COFs) constructed with metallocyclophane units and organic linkers have found application as electrocatalytic systems. Nevertheless, the majority of linkers within COFs necessitate intricate design and synthesis. Conversely, the potential utilization of natural building blocks in COF construction remains largely unexplored. In this study, we constructed a natural COF (CoPc-EA-COF) by employing a natural phenolic molecule (ellagic acid (EA)) as the linker and Co-hexadecafluorophthalocyanine (CoPc) as blocks. This framework serves as an electrocatalyst for both the oxygen reduction reaction (ORR) and carbon dioxide reduction reaction (CO 2 RR). The incorporation of EA units imparts the CoPc-EA-COF with elevated electronic conductivity, enhanced CO 2 binding affinity, and superior reductive capacity compared to the controlled COF lacking EA units. The CoPc-EA-COF demonstrated enhanced performance in the ORR, as evidenced by a half-wave potential of 0.80 V. Moreover, it showcased elevated activity and selectivity in the CO 2 RR, achieving a maximum CO faradic efficiency of 97.32 % at − 0.8 V, along with turnover frequency (TOF) values reaching 2092 h−1. Theoretical calculations revealed that the presence of EA units facilitated the generation of OOH* and COOH* species, which are pivotal in the rate-determining stages of both ORR and CO 2 RR processes. The contribution of EA units significantly bolstered the overall catalytic activity. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) are attractive as metal-free catalysts for the 2e− oxygen reduction reaction (ORR) towing to their tunable skeletons and porosities. However, the specific roles of their properties, such as crystallinity, porosity, dipole moment, and binding ability to reactants, in the catalytic performance are still unknown. In this work, we adopted a linker engineering strategy to reveal the crucial factors in determining the catalytic performance. The properties of the COFs were systematically engineered by altering the substituent groups in the linkers. The optimized Br-COF achieved a maximum selectivity of 86.2%, and a mass activity of 32.0 A g−1, which were 112% and 174% higher than those from unmodified COF, respectively. The experimental and theoretical results revealed that the reductive ability of the COFs exerted the most prominent effect on their catalytic activity and confirmed that the easy formation of an OOH* intermediate contributed to the high activity. [Display omitted] • We have developed seven catalytic COFs with the same topology and porosities, binding ability of O 2 , but possess reductive ability, and thus contributed tailored catalytic activity and selectivity (Br-> Cl-> OH-> OCH 3 -> F-> CH 3 -> H-COF). • The optimized Br-COF exhibited the highest activity and selectivity in the 2e− ORR, which were higher than other reported COFs. • The experimental and theoretical results revealed that the COF with strong reducing ability is easy to form OOH* intermediates, which makes its activity high. [ABSTRACT FROM AUTHOR]

Billions of people are suffering from a shortage of clean water. Covalent organic frameworks (COFs) based membranes show promise in supplying clean water from saline waters due to their designable and controllable porous structures. However, the challenge lies in the rejection of salt ions during the pervaporation process, which is attributed to the relatively large pore size of COFs. Herein, we report the 2D BTCA-TAPB- COF membranes supported on porous ceramics for efficient desalination. The resulting BTCA-TAPB-COF composite membrane consists of nanometer-thick BTCA-TAPB-COF lamellas, which are grown in an oriented manner by suppressing the surface energy. Through pervaporation, the membrane exhibits nearly complete NaCl rejections and high fluxes when processing NaCl solutions at seawater levels, surpassing the reported polymeric membranes. Moreover, the BTCA-TAPB-COF composite membrane exhibits reliable stability for desalination. Effects of desalination methods and charge states of solutes on the exclusion performance are comparatively investigated using BTCA-TAPB-COF composite membrane, which suggest that the surface charge of BTCA-TAPB-COF contributes to high ion rejection via the Donnan exclusion effect. [Display omitted] • Nanometer thick BTCA-TAPB-COF lamellas are obtained by surface energy suppression method. • 2D BTCA-TAPB-COF composite membranes are synthesized by layer-by-layer assembling. • BTCA-TAPB-COF membrane exhibits NaCl rejections >99.9% and high fluxes of ∼40 L m−2 h−1. • The COF composite membrane exhibits reliable stability for desalination. • Surface charge of membrane contributes to high ion rejection via Donnan exclusion. [ABSTRACT FROM AUTHOR]

[Display omitted] • The 1D COFs with alkynal units were constructed for improving OER activity. • The electronic conductivity and charge transfer ability can be modulated in 1D COFs. • The weaker stacking interaction between chains allowed expansion of the interlayer. • The DFT calculation revealed alkynal unites promoted OOH* desorption on Fe sites. Covalent organic frameworks (COFs) have been employed to catalyze the oxygen evolution reaction (OER). However, their catalytic activities have been limited, because their narrow interlayer space hindered the mass transport to the catalytic sites. Herein, we have demonstrated dimensional-controlled interlayer space of COFs for OER. The one dimensional (1D) catalytic COF had weaker stacking interaction between the 1D chains than that from two-dimensional COFs, which allowed for easier expansion of the interlayer distance in catalytic process, leading to enhanced catalytic activity. Moreover, the electronic states were well modulated with extending the length of conjugating units by integrating the alkynal units. The optimized catalyst achieved an overpotential of 225 mV and Tafel slope of 76 mV dec–1 in 1.0 M KOH, outperforming other 2D or 3D COFs. Theoretical calculations demonstrated that the alkynal units facilitated the OOH* desorption on the Fe sites, which further improved the activity. [ABSTRACT FROM AUTHOR]

A systematic computational study was performed in this work to investigate the dispersion behaviors of ionic liquids (ILs) in metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) as well as the separation performance of the resulting composites for CO 2 /CH 4 and CO 2 /N 2 mixtures. Five MOFs and eight COFs with diverse pore structures and chemical properties were selected as the supporters for 1-n-butyl-3-methy limidazolium thiocyanate [BMIM][SCN]. The results show that stronger Coulombic interactions contributed from the frameworks of MOFs can lead to better dispersion of the IL molecules in their pores compared with COFs. The gas separation performance can be significantly enhanced by introducing [BMIM][SCN] into MOFs and COFs, and MOFs can be considered as better support materials for ILs. Better dispersion of the IL in a given support material will induce greater enhancement on the separation performance of the composite, and such phenomenon is more evident for CO 2 /CH 4 mixture compared with the CO 2 /N 2 system. The IL molecules are more inclined to aggregate in the 2D-COFs and MOFs with 1D pore structures. However, they are more dispersive in the materials with 3D pore structures as the supporters, leading to a more evident improvement on the separation performance. This work also shows that using the materials containing strong adsorption sites like coordinatively unsaturated metal sites as the supporters for ILs cannot achieve significant enhancement on the gas separation performance of the composites. [ABSTRACT FROM AUTHOR]