A two-step synthesis of well-ordered cubic mesoporous silica materials under mildly acidic conditions

Abstract

Well-ordered mesoporous silica materials were synthesized by using poly(ethylene oxide- b-propylene oxide- b-ethylene oxide) triblock copolymer as template through two-step pathway under mildly acidic conditions (pH 2.2–4.1). The highly ordered cage-like mesoporosity of the prepared materials having cubic Fm3 m mesostructure was evidenced by the well-defined small angle X-ray diffraction patterns combined with transmission electron microscopy. Scanning electron microscopy observation exhibits a macron-sized spherical morphological structure for the prepared materials at pH 2.2, and a variation trend to small amount of spheres on the surface of randomly shaped agglomerations with increasing the pH value. The nitrogen adsorption–desorption analysis reveals that the prepared mesoporous silica materials have a uniform moderate-sized pore diameter (5.6–6.5 nm) and a very thick pore wall (4.96–6.10 nm). These features may lead to a much higher thermal, hydrothermal, and mechanical stability. The mesoporous silica materials synthesized in this study will 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 mildly acidic conditions can also be extended to the production in the industrial scale as an environmentally friendly way.