Interfacial Effect-Induced Electron Localization toward Pd Sites for Efficient Acetylene Semihydrogenation

Achieving high activity and ethylene selectivity under mild conditions is essential for the selective hydrogenation of acetylene but remains a formidable challenge. We report here a general yet powerful strategy to fabricate an excellent core–shell structured palladium-based catalyst (IL@Pd@NMC) with highly dispersed Pd nanoparticles embedded in an N-doped mesoporous carbon framework and then coated with a "soft" ionic liquid shell. The solid catalyst demonstrates outstanding selectivity (>93%) at full acetylene conversion over a wide temperature window (100–200 °C), which is of great significance for practical operations. Importantly, the catalyst exhibits remarkable stability without an obvious decay in performance during the long-term testing period (100 h). Detailed characterization has shown that the interfacial effect generated by the surrounding ionic liquid layer modulates the electronic structures of the Pd sites. The electron transfer toward Pd sites across the ionic liquid layer/metal interface considerably weakens ethylene adsorption, ensuring the easy desorption of ethylene. Meanwhile, the excellent heat transfer nature of the ionic liquid layer suppresses the formation of "hot spots" and thus greatly inhibits the formation of C4 byproducts, which is the key to the excellent stability of the catalyst. This work provides a promising strategy for designing new and efficient Pd-based catalysts for selective hydrogenation reactions.