Long chain ionic liquid-assisted synthesis of PS/Pd beads and hierarchical porous Pd-SiO₂

Long-chain ionic liquid, 1-hexadecyl-3-methylimidazolium chloride (C₁₆mimCl), was firstly used as a linking agent to construct polystyrene (PS)/C₁₆mimCl/palladium (Pd) beads. Subsequently, the PS/C₁₆mimCl/Pd beads were used as a macroporous templating agent and C₁₆mimCl was used as a mesoporous templating agent to prepare Pd-loaded hierarchical porous silica. A systematic study was carried out addressing the influence of the amount of C₁₆mimCl and the mass ratios of m(Pd)/m(PS) on the PS/C₁₆mimCl/Pd beads and the Pd-loaded hierarchical porous structures. The samples were characterized by electrophoresis experiments, SEM, TEM, small-angle XRD, and N₂ adsorption-desorption experiments. It was found that the coverage of citrate-coated Pd nanoparticles (Pd NPs) onto the PS beads can be simply tailored by changing the amount of C₁₆mimCl and the mass ratios of m(Pd)/m(PS). The resultant Pd-loaded hierarchical porous silica possessed a 3D ordered macroporous skeleton with a specific surface area of up to 967 m² g^-1, ordered mesoporous silica walls (SBA-3 type) and well-dispersed Pd NPs anchored on the inner walls of the spherical macroporous hollow. Importantly, the obtained Pd-loaded hierarchical porous silica exhibited an enhanced catalytic activity for the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H₂O₂.