Synergistic Metal-Nonmetal Active Sites in a Metal-Organic Cage for Efficient Photocatalytic Synthesis of Hydrogen Peroxide in Pure Water.

Abstract

Photocatalytic synthesis of hydrogen peroxide (H2O2) is a potential clean method, but the long distance between the oxidation and reduction sites in photocatalysts hinders the rapid transfer of photogenerated charges. Here, a metal-organic cage photocatalyst, Co14(L-CH3)24, is constructed by directly coordinating metal sites (Co sites) used for O2 reduction reaction (ORR) with non-metallic sites (imidazole sites of ligands) used for H2O oxidation reaction (WOR), which shortens the transport path of photogenerated electrons and holes, and improves the transport efficiency of charges and activity of photocatalyst. Therefore, it can be used as an efficient photocatalyst with a rate of as high as 146.6 μmol g-1 h-1 for H2O2 production under O2-saturated pure water without sacrificial agents. Significantly, the combination of photocatalytic experiments and theoretical calculations proves that the functionalized modification of ligands is more conducive to adsorbing key intermediates (*OH for WOR and *HOOH for ORR), resulting in better performance. This work proposed a new catalytic strategy for the first time, that is, to build a synergistic metal-nonmetal active site in the crystalline catalyst and use the host-guest chemistry inherent in MOC to increase the contact between the substrate and the catalytic active site, and finally achieve efficient photocatalytic H2O2 synthesis.