Mesoporous spherical silica encapsulating Pd nanoparticles prepared by CO 2 -induced mircoemulsion and catalytic application in Suzuki coupling reaction

The CO2-in-water (C/W) microemulsion was formed when the pressure of CO2 was above 4.0 MPa and has been investigated in-situ via high-pressure UV/vis spectra. The spherical mesoporous silica was successfully synthesized in CO2-induced microemulsion. Uniform spherical silica with a diameter of 102 ± 15 nm can be obtained by using C/W microemulsion as a template. It was observed that the BET area and pore volume of the spherical silica were enlarged with increasing the pressure of CO2. Moreover, Pd nanoparticles (Pd NPs) were encapsulated inside the spherical mesoporous silica through one-pot approach. Owing to the particular core–shell structure, this catalyst showed excellent recyclability in the Suzuki coupling reaction when compared with conventional Pd/SiO2 and Pd/C catalysts. The new strategy can be extended as a general approach to prepare other metal nanoparticles encapsulated in spherical mesoporous silica.