Relative Local Electron Density Tuning in Metal‐Covalent Organic Frameworks for Boosting CO₂Photoreduction

Abstract

The high electron density and efficient charge carrier separation are two important factors to affect photocatalytic activity, especially for the CO2 photoreduction reaction. However, the systematic studies on the structure‐functional relationship regarding the above two factors based on precisely structure model are rarely reported. Herein, as a proof‐of‐concept, we developed a new strategy on the evaluation of local electron density by controlling the relative electron‐deficient (ED) and electron‐rich (ER) intensity of monomer at a molecular level based on three rational‐designed vinylene‐linked sp2 carbon‐covalent organic frameworks (COFs). As expected, the as‐prepared vinylene‐linked sp2 carbon‐conjugated metal‐covalent organic framework (MCOFs) (VL‐MCOF‐1) with molecular junction exhibited excellent activities for CO2‐to‐HCOOH conversion (283.41 μmol g–1 h–1) and high selectivity of 97.1%, much higher than the VL‐MCOF‐2 and g‐C34N6‐COF, which is due to the synergistic effect of the multi‐electronic metal clusters (Cu3(PyCA)3) (PyCA = pyrazolate‐4‐carboxaldehyde) as strong ER roles and cyanopyridine units as ED roles and active sites, as well as the boosted photo‐induced charge separation efficiency of vinyl connection and increased light utilization ability. These results not only provide a strategy for regulating the electron‐density distribution of photocatalysts at the molecular level but also offers profound insights for metal clusters‐based COFs to effective CO2 conversion.

Three-Motif Molecular Junction Type Covalent Organic Frameworks for Efficient Photocatalytic Aerobic Oxidation

“…The molecular junction catalyst, which refers to the molecular structure formed by two functional groups such as oxidative and reductive agents, is one of the ideal types of catalyst to fulfill the coupling reaction. The two-motif molecular junction catalysts were first developed in our recent studies, which innovatively realized the coupling of oxidative and reductive reactions in one system, and were successfully used for artificial photosynthesis, photocatalytic hydrogen peroxide synthesis, organic photocatalysis, and so on. − However, further implementation of three or more functional groups to break through the limitations of multifunctionality for two-motif molecular junction catalysts has not been studied. The functional groups such as photosensitizer units, electron transport units, redox catalytic centers, and so on can be simultaneously introduced to the molecular junction materials to couple efficient light absorption, photoelectron conversion, and highly active catalytic sites. − Therefore, the modulation of multifunctional catalysts can be realized on the basis of multiple-motif molecular junction materials.…”

Three-Component Construction of Mesoporous Metal–Organic Frameworks and Their Incorporation into Solid Polymer Electrolytes for Li-Ion Conduction

“…We choose to explore the synthesis of MOFs with linker construction in situ because constructing both coordinative linkages and dynamic covalent linkages allows the formation of new organic linkers with extended length, which would provide mesopores for polymer chains and lithium salts. MOFs based on cyclic trinuclear Cu 3 (PyCA) 3 (HPyCA = 1 H -pyrazole-4-carbaldehyde) are of particular interest to us because they also provide Cu-based interacting sites, and their synthesis based on two kinds of linkages have been successfully demonstrated. − For example, JNM-7 was very recently synthesized from Cu 3 (PyCA) 3 and benzidine (BD), and the newly constructed linker endowed the material with a low band gap for efficient photocatalysis.…”

Tailored Cis–Trans Isomeric Metal–Covalent Organic Frameworks for Coordination Configuration-Dependent Electrochemiluminescence

“…20−22 Considering MCOF construction, building blocks are required to have both a stable coordination structure and a group that can be used to generate covalent bonds. The metal units in the currently reported MCOFs are limited to Cu-pyrazolate, 17,23 octahedral Ti IV , 16,24 and Ru II tris(2,2′-bipyridine) complexes. 19 low cost, are undoubtedly one of the candidate ligands to provide such complex coordination environments.…”

“…The precise location and microenvironment in MCOFs facilitate the comprehension of the relationship between structure and performance in catalysis. − Considering MCOF construction, building blocks are required to have both a stable coordination structure and a group that can be used to generate covalent bonds. The metal units in the currently reported MCOFs are limited to Cu-pyrazolate, , octahedral Ti IV , , and Ru II tris­(2,2′-bipyridine) complexes . Amino acids, which possess multiple coordinating heteroatoms with low cost, are undoubtedly one of the candidate ligands to provide such complex coordination environments.…”