Highly Selective Catalysis at the Liquid-Liquid Interface Microregion

Liquid-liquid interfaces in principle have the potential to regulate the selectivity of chemical reactions because of highly anisotropic microenvironments but have not yet been well exploited. Here, we present a liquid-liquid interface-based strategy to boost catalytic selectivity, exemplified by selective hydrogenation of alpha,beta-unsaturated aldehydes. The key to this success is the spatially controlled assembly of tubular catalyst particles, just at the narrow inner interfacial layer of Pickering emulsion water droplets. The catalyst particles that are assembled at the inner interfacial layer of water droplets exhibit much higher selectivity to C=O hydrogenation than ones located either at the outer interfacial layer, in the interior of droplets, or at the conventionally called Pickering emulsion interface. A selectivity of 92.0-98.0% to the thermodynamically and kinetically unfavorable C=O hydrogenation over the C=-C hydrogenation was achieved unexpectedly. Our strategy and the phenomena of interfacial catalysis reported here constitute an important supplement to the existing methods for tuning catalytic selectivity, providing tremendous opportunities to construct highly selective catalytic systems.