Fluorine-modified cobalt electrocatalyst for quinoline hydrogenation with water at room temperature

Abstract

The room temperature selective hydrogenation of quinolines to 1,2,3,4-tetrahydroquinolines (THQs) using a safe and clean hydrogen donor catalyzed by cost-effective catalysts is significant but challenging because of the difficult activation of quinolines and H2. Here, a fluorine-modified cobalt catalyst is synthesized via electroreduction of Co(OH)F precursor that exhibits high activity for electrocatalytic hydrogenation of quinolines by using H2O as the hydrogen source to produce THQs with up to 99% selectivity and 94% isolated yield under ambient conditions. F is revealed to enhance the adsorption of quinolines, and promote water activation to produce active atomic hydrogen (H*) by forming F−-K+(H2O)7 networks. A unique 1,4/2,3-addition pathway involving H* is proposed by combining experimental and theoretical results. Wide substrate scopes, scalable synthesis of bioactive precursors, expedient fabrication of deuterated analogues, and paired synthesis of tetrahydroquinoline and industrially important adiponitrile at a low voltage highlight the promising application of this methodology.