Construction of hollow core-shell ZnO@Co3O4 p-n heterojunction for CO2 cycloaddition under visible light irradiation

In comparison to a single semiconductor, constructing p-n heterojunctions represents an efficient strategy for enhancing photocatalytic activity because of their advantages in accelerating charge separation and promoting photoabsorption. Herein, we propose a novel metal-organic framework (MOF)-assisted and controlled pyrolysis strategy for constructing a hollow core-shell p-n heterojunction photocatalyst ZnO@Co3O4. It is worth noting that the hollow core-shell heterojunction not only provides abundant active sites but also significantly facilitates the separation of photogenerated charge carriers and accelerates electron transfer. Benefiting from the above advantages, the optimized ZnO@Co3O4(400,2), obtained by pyrolysis at 400 degree celsius for 2 h using Zn-MOF@Co-MOF as a precursor, exhibits high activity for the cycloaddition of CO2 and epichlorohydrin, resulting in a 94 % yield of 4-(chloromethyl)-1, 3-dioxolan-2-one under 1 bar CO2 pressure and visible light irradiation for 2 h, which is significantly superior to those of ZnO(400,2) (5 %), Co3O4(400,2) (38 %), and the physically mixed counterparts (55 %). This work provides insightful guidance for designing efficient photocatalysts aimed at CO2 cycloaddition, thereby achieving solar to high-value-added chemical conversion efficiencies.