Cooperative Photocarrier Utilization Enables Dual-Channel Alcohol Dehydrogenation for Benzimidazole Synthesis

Abstract

Photocatalytic oxidative dehydrogenative coupling of alcohols and o-phenylenediamines offers a sustainable route to benzimidazole, yet conventional systems suffer from severe charge recombination and largely underutilized photogenerated electrons, limited to single-channel hole activation. Herein, we report gold-nanoparticle-decorated hafnium metal–organic layers (Au/Hf-MOL), which achieve efficient utilization of photogenerated charge carriers via an aerobic dual-channel mechanism. Upon light irradiation, effective separation of photogenerated electrons and holes takes place over Au/Hf-MOL. The photogenerated electrons migrate onto the surface of Au nanoparticles (Au NPs) and activate molecular oxygen (O2) into superoxide radicals. These two reactive species, namely superoxide radicals and photogenerated holes, work cooperatively to realize dual activation of the α-C–H bonds in alcohol molecules. Combined experimental and theoretical analyses reveal that the anchored Au NPs not only boost spatial charge-carrier separation, but also facilitate the coadsorption of O2 and alcohol substrates. Consequently, the reaction energy barriers for oxygen activation and ethanol dehydrogenation are reduced. The optimized catalyst delivers an unprecedented benzimidazole (MBZ) formation rate of 10 mmol g–1 h–1 with 100% selectivity, outperforming state-of-the-art photocatalysts. In situ spectroscopy, radical tests and Density functional theory (DFT) calculations verify the synergistic dual-redox pathway. Furthermore, the catalyst exhibits robust cycling stability and broad substrate tolerance. This work establishes an O2-mediated dual-channel strategy to maximize photocarrier efficiency, offering a promising paradigm for high-value alcohol upgrading.