A two-step route to synthesis of small-pored and thick-walled SBA-16-type mesoporous silica under mildly acidic conditions

Highly ordered SBA-16-type mesoporous silica materials were synthesized by using poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) triblock copolymer (EO(132)-PO(50)-EO(132), Pluronic F108) as template through a two-step pathway under mildly acidic conditions (pH 2.15-4.50). The highly ordered cage-like mesoporosity of the prepared SBA-16-type mesoporous silica materials having Im3m cubic mesostructure was proved by the well-defined X-ray diffraction patterns combined with transmission electron microscopy. Scanning electron microscopy shows a variation from the spherical agglomerations to the randomly shaped ones with an increase of pH value. The nitrogen adsorption-desorption analysis reveals that the prepared SBA-16-type mesoporous silica materials have a uniform small-sized pore diameter (3.37-4.24 nm) and very thick pore wall (8.84-10.2 nm). These features may make the SBA-16-type mesoporous silica materials synthesized in this study favor the incorporation of catalytically active heteroatoms in silica frameworks, and the functionalization of organic groups for applications in catalysis, sensor and separation. The two-step synthetic method under the mildly acidic conditions can also be extended to the production in the industrial scale as an environmentally friendly way.