Interfacial Intensification in Aqueous Micelles Enables Highly Efficient Hydrogenation with Ultra-Low Pd Loading

Abstract Despite the wide implementation in laboratory and industrial synthesis, multiphase hydrogenation is often constrained by inherently low gas-liquid (G-L) mass transfer efficiency, stemming from the poor solubility and slow diffusion of hydrogen in aqueous media. Here, we report an interfacial intensification strategy that employs a terminal tertiary amine-modified foaming surfactant (C8-M2070) to construct a microbubble catalytic system. Through an in situ reduction strategy, and by taking advantage of the coordination interaction between C8-M2070 micelles and the metal catalyst, a micelle-stabilized Pd NPs solution was successfully prepared. The hydrophobic chain (C8) of C8-M2070 effectively stabilized the microbubbles through hydrophobic interactions. Using nitrobenzene hydrogenation as a model reaction, the C8-M2070 microbubble-micelle catalytic system achieves 99.8% aniline yield under mild conditions (25 °C, 1.5 MPa H2, 4 h) with an ultra-low Pd loading of only 118 ppm. The experimental investigations reveal that this aqueous micellar system substantially enlarges the G-L interfacial area via microbubbles, thereby effectively enhancing hydrogen mass transfer and dissolution. More importantly, efficient hydrogenation reactions can be driven at the microinterface with only a ppm-level palladium catalyst, highlighting the critical role of interfacial intensification in reducing noble metal consumption. This unique interfacial intensification strategy establishes a general and scalable paradigm for intensifying industrially important mass transfer-limited reactions.