UiO-66 framework equipped with cadmium-thiocatecholato moieties as photocatalyst bearing stable active sites and intrinsic photosensitizing units for hydrogen evolution reaction

Photocatalytic hydrogen evolution reaction (HER) represents one of the most promising technologies for sustainable development. Even though metal-organic framework (MOF), comprising rich topologies and tunable functionalities, is getting attention as a new generation of photocatalyst, a majority of them only provide unclear active sites along with the use of external noble-metal based photosensitizers and environmentally unfriendly scavengers. Therefore, it is urged to develop MOFs possessing structurally unambiguous active sites along with inherent photosensitizing units and execute photocatalytic HER with greener sacrificial reagents. Herein, we report a UiO-66-type framework, namely UiO-66-dcbdt-Cd (dcbdt2- = 1,4-dicarboxylatebenzene-2,3-dithiol), bearing Cd-thiocatecholato moieties as intrinsic photosensitizing units and structurally well-defined active sites for photocatalytic HER in H2O. UiO-66-dcbdt-Cd gave the best HER yield of 5.29 mmol g-1 and rate of 1.32 mmol g-1 h-1, outperforming the negligible HER performance of pristine metal-free UiO-66-dcbdt. This work provides insight to manipulation of thiocatecholate functionalities inside MOFs to construct inherent photosensitizing units as well as stable structurally unambiguous active sites for sustainable photocatalytic applications.