Synthesis of Silica Hollow Nanoreactors with Finely Engineered Inner/Outer Surface Properties

摘要

In an attempt to mimic bio-synthetic systems with unique microenvironment and structure for allowing organic reactions taking place in water phase with high efficiency, here, we report for the synthesis of ultra-small silica hollow nanoreactors (particle size of 18 ± 2 nm) with finely engineered inner and outer hydrophilic/hydrophobic surface properties using phenyltrimethoxysilane (PTMS) and tetramethoxysilane (TMOS) as precursors and F127 (EO106PO70EO106) as single micelle template. Through tuning the mass ratio of PTMS/TMOS, selective growing of organic compositions in the interior or exterior surfaces could be observed. At PTMS/TMOS mass ratio less than 1/3, phenyl group was integrated in the inner surface due to the diffusion and condensation of hydrophobic PTMS into the hydrophobic core of F127 single micelle, inducing unique hydrophobic inner@hydrophilic outer surface properties. At high PTMS/TMOS ratio, phenyl group could be incorporated in both the inner and outer surface, resulting in hydrophobic surfaces. After depositing Pd species, the solid nanoreactor with hydrophobic inner and hydrophilic outer surface properties showed better catalytic performances than nanoreactors with either hydrophilic or hydrophobic surface properties in the aqueous phase hydrogenation of 4-nitrophenol (TOF 552 vs 312, 273 h~(-1)), showing the superiority of former nanoreactors in chemical reactions using water as solvent.