Semiconductor–redox catalysis promoted by metal–organic frameworks for CO2 reduction

Abstract

A noble-metal-free system for photochemical reduction of CO₂ has been developed by integrating graphitic carbon nitride (g-C₃N₄) with a cobalt-containing zeolitic imidazolate framework (Co-ZIF-9). g-C₃N₄ acts as a semiconductor photocatalyst, whereas Co-ZIF-9 is a cocatalyst that facilitates the capture/concentration of CO₂ and promotes light-induced charge separation. The two materials cooperate efficiently to catalyze CO₂-to-CO conversion upon visible light illumination under mild reaction conditions. A ¹³C-labelled isotropic experiment proved that CO₂ is the carbon source of the produced CO. Even without noble metals, the system still achieved an apparent quantum yield of 0.9 percent. The system displayed high photocatalytic stability, without noticeable alterations in the chemical and crystal structures of g-C₃N₄ and Co-ZIF-9 after the reaction.