Selective photosynthesis of imines from biomass-derived aldehydes over Ni/TiO 2

Photocatalytic reductive amination of biomass-derived aldehydes is a desirable way to selectively upgrade biomass into value-added nitrogen-containing chemicals under mild conditions. However, it is challenging to produce imines in high selectivity because of the undesirable side reactions caused by the activity of functional groups. Here, we demonstrate the highly reactive and selective production of imines from biomass derived aldehydes via the photocatalytic reductive amination, using a defective TiO 2 supported nickel catalyst. The employment of methanol as the hydrogen donor and ammonia solution as the nitrogen source avoids the use of high-pressure H 2 and expensive amines, rendering the current catalytic process safe, economical, and environmentally friendly. In depth investigations attribute the improved separation and transfer of photogenerated charge carriers to the presence of oxygen vacancies and decorated Ni nanoparticles, thereby accelerating the production of imines from benzaldehyde amination (conversion, 95.8%; selectivity, 95.2%). Furthermore, the developed system could be easily translated to the photocatalytic conversions of various biomass derived aldehydes, which provided an example of a cost-effective and sustainable approach for the valorization of biomass derived feedstocks. Graphic abstract