Confining and Highly Dispersing Single Polyoxometalate Clusters in Covalent Organic Frameworks by Covalent Linkages for CO₂ Photoreduction

Abstract

Single clusters have attracted extensive research interest in the field of catalysis. However, achieving a highly uniform dispersion of a single-cluster catalyst is challenging. In this work, for the first time, we present a versatile strategy for uniformly dispersed polyoxometalates (POMs) in covalent organic frameworks (COFs) through confining POM cluster into the regular nanopores of COF by a covalent linkage. These <b>COF-POM</b> composites combine the properties of light absorption, electron transfer, and suitable catalytic active sites; as a result, they exhibit outstanding catalytic activity in artificial photosynthesis: that is, CO₂ photoreduction with H₂O as the electron donor. Among them, <b>TCOF-MnMo</b>_<b>6</b> achieved the highest CO yield (37.25 μmol g^-1 h^-1 with ca. 100% selectivity) in a gas-solid reaction system. Furthermore, a mechanism study based on density functional theory (DFT) calculations demonstrated that the photoinduced electron transfer (PET) process occurs from the COF to the POM, and then CO₂ reduction and H₂O oxidation occur on the POM and COF, respectively. This work developed a method for a uniform dispersion of POM single clusters into a COF, which also shows the potential of using <b>COF-POM</b> functional materials in the field of photocatalysis.