Noble-metal-free cobaloxime coupled with metal-organic frameworks NH2-MIL-125: A novel bifunctional photocatalyst for photocatalytic NO removal and H2 evolution under visible light irradiation.

The novel bifunctional NH2-MIL-125/Co(dmgH)2 composite catalysts with several different Co(dmgH)2 contents that can simultaneously achieve photocatalytic NO removal and hydrogen production were first prepared by a simple and convenient method. The corresponding physical and chemical properties of the composite catalysts were characterized by SEM, XRD, ESR, in situ DRIFTS, etc. The characterization results indicated that the noble-metal-free Co(dmgH)2, which was much cheaper and more available than most noble-metals such as Pt, could be an effective co-catalyst to accelerate the separation of photogenerated electron-hole pairs, further eventually enhancing the photocatalytic efficiency. Under visible-light irradiation for half an hour, the NO removal ratio of NH2-MIL-125/Co(dmgH)2 (3 wt%) increased by 22.7 % compared with the pristine NH2-MIL-125 without Co(dmgH)2 loading. In addition, it was found that Eosin Y dye-sensitized NH2-MIL-125/Co(dmgH)2 (3 wt%) was capable of promoting a hydrogen generation rate of 2195 µmol g-1 h-1 under visible light, which was 12.6 times greater than the original NH2-MIL-125. This strategy was expected as an available way to fabricate noble-metal-free molecular complexes with metal-organic frameworks (MOFs) to enhance the photocatalytic NO removal and hydrogen production performance simultaneously.