Fabrication of core–shell-like structured polymeric ionic liquid hybrid catalysts for aqueous reactions

Abstract

Core–shell-like structured polymeric ionic liquid hybrid nanoreactors with “internal hydrophobic–external hydrophilic” characteristics were successfully synthesized through the Stöber method and reversible addition–fragmentation chain transfer (RAFT) polymerization. Firstly, we introduced hydrophobic organosilicon as an inner core and fixed Pd nanoparticles (∼0.69 mmol g⁻¹) in the pore and finally constructed a hydrophilic shell, which not only ensured the dispersity of the catalyst in water but also effectively prevented the leaching of Pd species. The structure and properties of nMIE@Pd/SiNP-CPDB were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N₂ adsorption–desorption, ICP-OES, thermogravimetric analysis (TGA) and ultraviolet and visible spectrophotometry (UV-vis) characterization methods. The adsorption enthalpy of the best catalyst for styrene was calculated using the Clausius–Clapeyron equation and the value was −12.765 kJ mol⁻¹, which strongly verified that the prepared catalyst could effectively promote mass transfer and the adsorption of reactants or products. Furthermore, the as-prepared nanoreactors exhibit distinguished catalytic activity for aqueous hydrogenation reactions and even after 7 cycles, the catalysts still maintain their superior catalytic activity, showing almost no leaching of palladium species.