A Time-Interval Strategy to Prepare Porous SiO₂ Spheres with Adjustable Core-Shell Ratio for Multiple Guest Loading

Porous microspheres with desired pore size and distribution are in high demand for loading various guest materials, especially various pollutants that are several nanometers in size or stably suspended in liquid. Herein, multilevel porous SiO₂ microspheres with arbitrarily adjustable core-shell ratios are prepared by solely regulating the time interval between the start of the hydrolysis reaction and the addition of organic solvent. The core-shell ratio of the SiO₂ microspheres increases gradually with prolongation of the addition time interval; meanwhile, the specific surface area can be adjusted from 543.2 m² g^-1 to 992.9 m² g^-1, and the average pore diameter varies from 2.3 to 5.7 nm together with a high pore volume reaching 0.91 cm³ g^-1. Moreover, the hierarchical core-shell SiO₂ microspheres with an adjustable core-shell ratio, a large specific surface area, and a multilevel pore size could be obtained on a large scale. These SiO₂ microspheres demonstrate excellent performance in coloading platinum nanoparticles and various dye molecules, suggesting their great potential in treating various pollutants in printing and dyeing wastewater.