Efficient acceptorless dehydrogenation of hydrogen-rich N-heterocycles photocatalyzed by Ni(OH)2@CdSe/CdS quantum dots

Hydrogen storage using liquid organic hydrogen carriers (LOHCs) is a promising hydrogen storage technology; however, the hydrogen release process typically requires a high temperature. Developing dehydrogenation technology under mild conditions is highly desirable. Herein, a new approach for photocatalytic acceptorless dehydrogenation of hydrogen-rich LOHCs using Ni(OH)2@CdSe/CdS QDs as the photocatalyst was demonstrated. 1,2,3,4-Tetrahydroquinoline (THQ), iso-THQ, indoline, and their derivatives were selected as hydrogen-rich substrates, which exhibit excellent dehydrogenation efficiency with the release of hydrogen photocatalyzed by Ni(OH)2@CdSe/CdS QDs. Up to 100% yields of hydrogen and over 90% yields of complete dehydrogenation products were obtained at ambient temperature. Isotope tracer studies indicate a stepwise pathway, beginning with the photocatalytic oxidation of the substrate to release a proton and followed by proton exchange with heavy water. This work provides a promising alternative strategy to develop highly efficient, low cost and earth-abundant photocatalysts for acceptorless dehydrogenation of hydrogen-rich LOHCs.