Dual-functional photocatalysis boosted by electrostatic assembly of porphyrinic metal-organic framework heterojunction composites with CdS quantum dots

Abstract

Photocatalytic dual-functional reaction under visible light irradiation represents a sustainable development strategy. In detail, H2 production coupled with benzylamine oxidation can remarkably lower the cost by replacing sacrificial agents. In this work, CdS quantum dots (CdS QDs) were successfully loaded onto the surface of a porphyrinic metal-organic framework (Pd-PCN-222) by the electrostatic self-assembly at room temperature. The consequent Pd-PCN-222/CdS heterojunction composites displayed superb photocatalytic activity under visible light irradiation, achieving a H2 production and benzylamine oxidation rate of 5069 and 3717 µmol g−1 h−1 with >99% selectivity in 3 h. There is no noticeable loss of catalytic capability during three successive runs. Mechanistic studies by in situ electron spin resonance and X-ray photoelectron spectroscopy disclosed that CdS QDs injected photoexcited electrons to Pd-PCN-222 and then Zr6 clusters under visible-light irradiation, and thus CdS QDs and Zr6 clusters behave as the photocatalytic oxidation and reduction centers, respectively.