Remarkably boosting catalytic H2 evolution from ammonia borane through the visible-light-driven synergistic electron effect of non-plasmonic noble-metal-free nanoparticles and photoactive metal-organic frameworks

From the viewpoint of regulating and enriching the electron density of noble-metal-free nanoparticles (NPs) to remarkably enhance their catalytic activities in the reduction-dominated reactions, we synthesized a series of non-plasmonic Co and Ni nanoparticles (NPs) supported by NH2-functionalized photoactive and NH2-free non-photoactive metal-organic frameworks (MOFs) with different compositions and framework structures, which were used to catalyze H2 evolution from ammonia borane (NH3BH3) in aqueous solution under visible light irradiation at 298 K. The systematic investigation showed that the catalysts containing photoactive MOFs had higher activities than those containing non-photoactive MOFs under visible light irradiation though the photocatalytic activities of all the catalysts were enhanced in comparison with the activities in the dark. Specifically, the Co catalysts containing photoactive MOFs had the total turnover frequency (TOF) values in the range of 81.7–117.7 min−1, which were much higher than the values of reported noble-metal-free catalysts and were even comparable to the values of noble metal catalysts. The remarkably enhanced activities of the supported catalysts could be attributed to the visible-light-driven synergistic electron effect of semiconductor-like MOFs and non-plasmonic noble-metal-free NPs, which was verified by the increased photocurrent density of Co/MIL-101(Cr)-NH2. Moreover, the catalysts still had 100% of H2 selectivity and high activities after 25 runs of catalysis.