Encapsulating a Ni(II) molecular catalyst in photoactive metal-organic framework for highly efficient photoreduction of CO.

Photocatalytic reduction of CO to CO is a promising strategy for reducing atmospheric CO levels and storing solar radiation as chemical energy. Here, we demonstrate that a molecular catalyst [Ni(bpet)(HO)] successfully encapsulated into a highly robust and visible-light responsive metal-organic framework (Ru-UiO-67) to fabricate composite catalysts for photocatalytic CO reduction. The composite Ni@Ru-UiO-67 photocatalysts show efficient visible-light-driven CO reduction to CO with a TON of 581 and a selectivity of 99% after 20-h illumination, because of the facile electron transfer from Ru-photosensitizer to Ni(II) active sites in Ni@Ru-UiO-67 system. The mechanistic insights into photoreduction of CO have been studied based on thermodynamical, electrochemical, and spectroscopic investigation, together with density functional theory (DFT) calculations. This work shows that encapsulating molecular catalyst into photoactive MOF highlights opportunities for designing efficient, stable and recyclable photocatalysts.