Photoreduction of carbon dioxide under visible light by ultra-small Ag nanoparticles doped into Co-ZIF-9.

Metal-organic frameworks (MOFs) are well-known porous materials able to adsorb CO, and their performance in CO reduction has attracted much attention from researchers. A classical Co-MOF, Co-ZIF-9, has been proposed as a novel photocatalyst for reducing CO into chemical feedstocks. Herein, Co-ZIF-9 with a rod-like structure was obtained through reflux. Ultra-small silver nanoparticles (Ag NPs, smaller than 5 nm) were doped into Co-ZIF-9 by the photodeposition method. With the assistance of a photosensitizer, the resultant composite Ag@Co-ZIF-9 shows catalytic reactivity in converting CO into CO under visible light irradiation. Compared with bare Co-ZIF-9, the photocatalytic performance of Ag@Co-ZIF-9 increases by more than twofold (around 28.4 μmol CO) and the selectivity is enhanced by about 20% (22.9 μmol H) for 0.5 h of irradiation. This demonstrates that Ag NPs doping may provide a possible way to promote the efficiency and selectivity of MOF materials in CO photoreduction.