Integrating carbon quantum dots with oxygen vacancy modified nickel-based metal organic frameworks for photocatalytic CO reduction to CH with approximately 100 % selectivity.

Solar-light-driven reduction of CO into renewable fuels has great potential in the production of sustainable energy, addressing the energy crisis and environmental problems simultaneously. However, it is a significant challenge to achieve high selectivity for the conversion of CO into CH, which is a type of fuel with a high calorific value. Herein, carbon quantum dots (CQDs) were integrated with an oxygen vacancy modified nickel-based metal organic frameworks (NiMOFs) to form the CQDs-X/NiMOF series, which exhibited superior performance for CO photoreduction into CH compared with pure NiMOFs in the presence of hole scavengers under visible light irradiation. The highest yielding rate of CH (1 mmol g h) and selectivity (97.58 %) were obtained using a CQDs-25/NiMOF catalyst. Most importantly, in diluted CO atmosphere, the yield of CH was almost unchanged and the selectivity of CH over CQDs-25/NiMOF was higher than that in pure CO. The superior performance of CQDs-25/NiMOF may be attributed to the following two factors: (i) both CQDs and oxygen vacancies facilitate the transmission of electrons to promote the eight-electron reaction producing CH, and (ii) oxygen vacancies can act as the electron trap to capture the photogenerated electrons to react with adsorbed CO on Ni. This study offers a valuable strategy for designing efficient photocatalysts to convert CO into CH with superior selectivity.