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Abstract

Direct hydrogenation of C=C double bonds is a basic transformation in organic chemistry which is vanishing from simple practice due to the need for pressurized hydrogen. Ammonia borane (AB) has emerged as a unique hydrogen source due to its safety and high hydrogen content. However, in conventional systems the hydrogen liberated from the high-cost AB cannot be fully utilized. Herein, we develop a novel Pd/g-C₃N₄ stabilized Pickering emulsion microreactor, in which alkenes are hydrogenated in the oil phase with hydrogen originating from AB in the water phase, catalysed by the Pd nanoparticles at the interfaces. Notably, unit efficiency of hydrogen utilization is achieved within this microreactor, benefiting from the hydrogen storage capability of the emulsion via hydrogen concentrating at the Pd sites and in the liquid phases, whilst availabe for further hydrogenation until depletion. This buffer effect proves advantageous for more economical hydrogen utilization over conventional systems. The emulsion microreactor can be applied to a range of alkene substrates, with the conversion rates achieving > 95% by a simple modification.