Interfacial Synergy of Ni Single Atom/Clusters and MXene Enabling Semiconductor Quantum Dots Based Superior Photoredox Catalysis

Semiconductor-based photocatalysis has evolved over the past decade into a prevalent approach for alcohol oxidation to afford the corresponding carbonyl compounds or C–C/C–O coupled products. Nonetheless, photocatalytic oxidative lactonization of diols to lactones still significantly lags behind, even though lactones represent a class of ring moieties with excellent biological activities. In this work, we present the high-performance visible-light-mediated lactonization of diols to lactones and H₂ over the Ti₃C₂T_x MXene-supported CdS quantum dots (QDs) with Ni decoration (Ni/CdS/Ti₃C₂T_x). Ti₃C₂T_x acts as a two-dimensional platform for immobilizing CdS to promote the separation and migration of charge carriers, while concomitantly the Cd²⁺ confinement effect of Ti₃C₂T_x significantly retards the hole-induced photocorrosion of CdS. The unique modifications of atomically dispersed Ni species are either incorporated as Ni clusters in CdS to accelerate H₂ evolution, or anchored as a Ni single atom on Ti₃C₂T_x for the efficient adsorption and cyclization of diols. The optimized Ni/CdS/Ti₃C₂T_x exhibits remarkably enhanced activity for lactone synthesis, which is 80.4 times higher than that of blank CdS, along with excellent selectivity and high durability. This work brings a conceptual idea to overcome the well-known intrinsic drawback of photoinduced decomposition in semiconductor-based photocatalysts and offers a generic and robust strategy of utilizing atomically dispersed cocatalyst as active sites for efficient and robust photoredox lactones synthesis and H₂ evolution.