Pore-expansion of organically functionalized monodispersed mesoporous silica spheres and pore-size effects on adsorption and catalytic properties

In this paper, we report on the pore-expansion of organically functionalized monodispersed mesoporous silica spheres (MMSS) and their use as adsorbents for bulky dyes as well as proteins. Solvothermal treatment under a water/ethanol mixture led to pore-expansion of the organically functionalized MMSS while retaining their organic functionality and high monodispersity. Mesopores were expanded to 3.5 nm from 2.5 nm for amino-functionalized MMSS, and to 3.3 nm from 2.4 nm for carboxyl-functionalized MMSS. TEM observations revealed that the mesopores were aligned radially from the center towards the outside of the spheres, as observed in the previously reported MMSS without organic groups. It was confirmed that pore-expanded organically functionalized MMSS showed excellent adsorption properties for bulky dye molecules and proteins. In addition, trypsin-immobilized carboxyl-functionalized MMSS with large mesopores showed high catalytic activity. The turnover frequency in hydrolysis was enhanced by 1.5 times compared to the original particles.