Facile synthesis of ZnCdS quantum dots via a novel photoetching MOF strategy for boosting photocatalytic hydrogen evolution

MOF self-sulfurizing is regarded as a promising approach for preparing quantum dots (QDs). Herein, ZnCdS QDs were constructed by photoetching self-sulfurization of a novel 3D metal-organic framework (namely PZH) for the first time. The results of the morphology and X-ray diffraction (XRD) characterizations show that the ZnCdS QDs do not self-aggregate, and the frame structure of PZH remain intact. Under visible-light irradiation, ZnCdS QDs/PZH with the photoetching time of 60 min (ZnCdS_3/PZH) exhibits a remarkably enhanced photocatalytic hydrogen production rate with an apparent quantum efficiency (AQE) of 18.51 % at 420 nm. The improvement of photocatalytic activity can be predominantly attributed to an outstanding four synergism of promoting separation and transfer of carriers owing to ZnCdS QDs shortening the charge transmission distance, inhibiting the recombination of photogenerated electron-holes of uniform dispersed quantum dots without aggregating, optimizing the adsorption behavior of the active intermediates (H*) owing to the synergistic action between ZnCdS QDs and PZH, offering more holes for reactant molecules transmission due to presence of PZH. The density functional theory (DFT) calculation reveals that ZnCdS quantum dots relative to large size S-ZnCdS is going to help reduce the Gibbs free energy of photocatalytic hydrogen evolution reaction. More importantly, this rare strategy not only flourish the design idea of quantum dots, but also promote the applications of MOF in photocatalytic H2 production.