Covalent organic frameworks (COFs) are promising candidates for electrocatalytic reduction of carbon dioxide into valuable chemicals due to their porous crystalline structures and tunable single active sites, but the low conductivity leads to unmet current densities for commercial application. The challenge is to create conductive COFs for highly efficient electrocatalysis of carbon dioxide reduction reaction (CO2RR). Herein, a porphyrin‐based COF containing donor–acceptor (D–A) heterojunctions, termed TT‐Por(Co)‐COF, is constructed from thieno[3,2‐b]thiophene‐2,5‐dicarbaldehyde (TT) and 5,10,15,20‐tetrakis(4‐aminophenyl)‐porphinatocobalt (Co‐TAPP) via imine condensation reaction. Compared with COF‐366‐Co without TT, TT‐Por(Co)‐COF displays enhanced CO2RR performance to produce CO due to its favorable charge transfer capability from the electron donor TT moieties to the acceptor Co‐porphyrin ring active center. The combination of strong charge transfer properties and enormous amount of accessible active sites in the 2D TT‐Por(Co)‐COF nanosheets results in good catalytic performance with a high Faradaic efficiency of CO (91.4%, −0.6 V vs reversible hydrogen electrode (RHE) and larger partial current density of 7.28 mA cm−2 at −0.7 V versus RHE in aqueous solution. The results demonstrate that integration of D–A heterojunctions in COF can facilitate the intramolecular electron transfer, and generate high current densities for CO2RR.

The unique applications of porous metal–organic framework (MOF) liquids with permanent porosity and fluidity have attracted significant attention. However, fabrication of porous MOF liquids remains challenging because of the easy intermolecular self‐filling of the cavity or the rapid settlement of porous hosts in hindered solvents that cannot enter their pores. Herein, we report a facile strategy for the fabrication of a MOF liquid (Im‐UiO‐PL) by surface ionization of an imidazolium‐functionalized framework with a sterically hindered poly(ethylene glycol) sulfonate (PEGS) canopy. The Im‐UiO‐PL obtained in this way has a CO2 adsorption approximately 14 times larger than that of pure PEGS. Distinct from a porous MOF solid counterpart, the stored CO2 in Im‐UiO‐PL can be slowly released and efficiently utilized to synthesize cyclic carbonates in the atmosphere. This is the first example of the use of a porous MOF liquid as a CO2 storage material for catalysis. It offers a new method for the fabrication of unique porous liquid MOFs with functional behaviors in various fields of gas adsorption and catalysis.

Metrics & MoreArticle Recommendations * sı Supporting Information CONSPECTUS:The continuing increase of the concentration of atmospheric CO 2 has caused many environmental issues including climate change. Catalytic conversion of CO 2 using thermochemical, electrochemical, and photochemical methods is a potential technique to decrease the CO 2 concentration and simultaneously obtain value-added chemicals. Due to the high energy barrier of CO 2 however, this method is still far from large-scale applications which requires high activity, selectivity, and stability. Therefore, development of efficient catalysts to convert CO 2 to different products is urgent. With their well-engineered pores and chemical compositions, high surface area, elevated CO 2 adsorption capability, and adjustable active sites, porous crystalline frameworks including metal−organic frameworks (MOFs) and covalent organic frameworks (COFs) are potential materials for catalytic CO 2 conversion.Here, we summarize our recent work on MOFs and COFs for thermocatalytic, electrocatalytic, and photocatalytic CO 2 conversion and describe the structure−activity relationships that could guide the design of effective catalysts.The first section of this paper describes imidazolium-functionalized porous MOFs, including porous liquid and cationic MOFs with nucleophilic halogen ions, which can promote thermocatalytically CO 2 cycloaddition reaction with epoxides toward cyclic carbonates at one bar pressure. A porous liquid MOF takes on the role of a CO 2 reservoir to tackle the low local CO 2 concentrations in gas−liquid−solid heterogeneous reactions. Imidazolium-functionalized MOFs with halogen ions for CO 2 cycloaddition could avoid the use of cocatalysts, and this leads to milder and more facile experimental conditions and separation processes.In a section dealing with the electrocatalytic CO 2 reduction reaction (CO 2 RR), we developed a series of conductive porous framework materials with fast electron transmission capabilities, which afford high current densities and outperform the traditional MOF and COF catalysts that have been reported. The intrinsically conductive two-dimensional 2D MOFs and COFs nanosheets based on the fully π-conjugated phthalocyanine motif with excellent electron transport capability were prepared, and strong electron transporters were also integrated into metalloporphyrin-based COFs for CO 2 RR. Cu 2 O quantum dots and Cu nanoparticles (NPs) can be uniformly dispersed on porous conductive MOFs/COFs to afford synergistic and/or tandem electrocatalysts, which can achieve highly selective production of CH 4 or C 2 H 4 in CO 2 RR. A third section describes our efforts to facilitate electron−hole separation in CO 2 photocatalysis. Our focus is on regulation of coordination spheres in MOFs, fabrication of the architecture of MOF heterojunctions, and engineering MOF films to facilitate photocatalytic CO 2 reduction. Finally, we discuss several problems associated with the studies of MOFs and COFs for CO 2 conversion and consider some pros...