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

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.