ZIF-8 derived Ag/ZnO photocatalyst with enriched Ag-ZnO interface for effective oxidation of methane to liquid oxygenates with simultaneous mmol-scale productivity and ∼100 % selectivity

Abstract

Achieving a high yield of oxygenates and inhibiting overoxidation remain challenging for CH4 photooxidation. Here, we report a catalyst with enriched Ag-ZnO interfaces by using ZIF-8 as the precursor. The resulting Ag/Z-450 photocatalysts show extraordinary efficiency in the photocatalytic oxidation of CH4, a high liquid oxygenate yield of 57.88 mmol·gcat−1 (28.94 mmol·gcat−1·h−1) and a selectivity of ∼100 % were obtained over 3.0Ag/Z-450, with HCHO as the major product (41.04 mmol·gcat−1, ∼71 % selectivity). Mechanistic studies revealed that ZnO and Ag species acted as electron donors and acceptors, respectively, which enhanced charge carriers transfer and separation. CH4 and O2 can be effectively activated to generate •CH3 and reactive oxygen species (ROS), their following reaction led to formation of CH3OOH, which can be further converted to CH3OH and HCHO. This work contributes to the development of a “two-in-one” CH4 photooxidation catalyst system that simultaneously achieves unparallel productivity and selectivity.