Confining and Highly Dispersing Single Polyoxometalate Clusters in Covalent Organic Frameworks by Covalent Linkages for CO 2 Photoreduction.

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 COF-POM 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, CO 2 photoreduction with H 2 O as the electron donor. Among them, TCOF-MnMo 6 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 CO 2 reduction and H 2 O 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 COF-POM functional materials in the field of photocatalysis.