Decoration of Defective Sites in Metal–Organic Frameworks to Construct Tight Heterojunction Photocatalyst for Hydrogen Production

Zr–metal–organic frameworks (MOFs) have received much interest for their ultrahigh stability and are considered an up-and-coming class of catalysts for photocatalytic water splitting. However, their activity still needs to be improved. In this work, a series of defective UiO-66-NH2-x@CdS nanoparticles (NPs) (x = 0, 50, 100, 150, 200, denotes the molar equivalent of the defect modulator) heterostructure photocatalysts is constructed for water splitting using defect engineering followed by a postmodification strategy. Defective structures are introduced to improve the photocatalytic activity of heterojunctions in the following ways: 1) modulating the energy band structure of UiO-66-NH2-x, 2) providing chelate binding sites for modifying the bridging molecules and thus building strong interactions between UiO-66-NH2-x and CdS NPs, and 3) serving as trapping sites to separate the photogenerated electron–hole pairs. Hence, this constructed series of UiO-66-NH2-xCdS NPs exhibit ultrahigh photocatalytic water splitting for H2 production, especially UiO-66-NH2-150@CdS NPs with moderately defective levels showing catalytic activity up to 2303 μmol g−1 h−1, which is 2.36 times higher than pure CdS NPs. Furthermore, the heterojunction catalysts with different defect levels exhibit a volcano-type trend, demonstrating the feasibility of defect engineering. This work provides novel insights for developing advanced defect-based MOF-constructed composite photocatalysts.