Vinylene‐Linked Donor‐π‐Acceptor Metal‐Covalent Organic Framework for Enhanced Photocatalytic CO2 Reduction

Intramolecular charge separation driving force and linkage chemistry between building blocks are critical factors for enhancing the photocatalytic performance of metal-covalent organic framework (MCOF) based photocatalyst. However, robust achieving both simultaneously has yet to be challenging despite ongoing efforts. Here we develop a fully π-conjugated vinylene-linked multivariate donor-π-acceptor MCOF (D-π-A, termed UJN-1) by integrating benzyl cyanides linker with multiple functional building blocks of electron-rich triphenylamine and electron-deficient copper-cyclic trinuclear units (Cu-CTUs) moieties, featuring with strong intramolecular charge separation driving force, extended conjugation degree of skeleton, and abundant active sites. The incorporation of Cu-CTUs acceptor with electron-withdrawing ability and concomitantly giant charge separation driving force can efficiently accelerate the photogenerated electrons transfer from triphenylamine to Cu-CTUs, revealing by experiments and theoretical calculations. Benefiting from the synergistically effect of D-π-A configuration and vinylene linkage, the highly-efficient charge spatial separation is achieved. Consequently, UJN-1 exhibits an excellent CO formation rate of 114.8 μmol g^-1 in 4 h without any co-catalysts or sacrificial reagents under visible light, outperforming those analogous MCOFs with imine-linked (UJN-2, 28.9 μmol g^-1) and vinylene-linked COF without Cu-CTU active sites (UJN-3, 50.0 μmol g^-1), emphasizing the role of charge separation driving force and linkage chemistry in designing novel COFs-based photocatalyst.