Photoredox-promoted co-production of 3,4-dihydroisoquinoline and H2 over Pd-doped leaf-like CdS catalyst

Integrating selective organic transformation and hydrogen (H2) evolution in one photoredox reaction system is one of the most sustainable and promising approaches to efficiently produce solar fuels and chemicals by simultaneously utilizing photogenerated electrons and holes. Herein, through the cation-exchange engineering method, the nanoleaf-like Pd/CdS composites are gingerly fabricated for visible-light-driven receptor-free dehydrogenation of 1,2,3,4-tetrahydroisoquinoline (THIQ) to 3,4-dihydroisoquinoline (DHIQ) and H2 under ambient conditions. The optimized electronic structure endows Pd/CdS with a narrow band gap and suitable energy band positions, thus facilitating the light harvesting as well as the separation and transfer of photoexcited charge carriers. Consequently, the Pd/CdS exhibits significantly improved photoredox activity compared to bare CdS. In-situ Fourier-transform infrared spectroscopy and electron paramagnetic resonance spectroscopy track the progression of reaction intermediates during such a dual-functional photoredox-catalyzed system, revealing that the carbon-centered radical is the key reaction intermediate in this reaction process. It is anticipated that this work would guide the rational utilization of CdS-based materials to enable simultaneous photochemical coupling of organic transformation and H2 evolution.