Monodisperse Aluminosilicate Spheres with Tunable Al/Si Ratio and Hierarchical Macro-Meso-Microporous Structure

While tremendous success has been seen in the development of ordered mesoporous silica by soft-templated methods, synthesis of hierarchical structures with controllable multiscale pore networks has remained a challenging topic. On the other hand, introduction of heteroatoms as an effective method of chemically functionalizing silica leads to difficulties in morphological control of the product, and multistep synthesis has been necessary for functionalized silica particles with hierarchical pore structure and uniform size. The present work demonstrates that the conflict between morphological control and heteroatom incorporation can be resolved in a CTAB-stabilized toluene-water-ethanol microemulsion system. For the first time, monodisperse macro-meso-microporous aluminosilicate spheres (MASS) are synthesized in one step at room temperature. Simultaneous tuning of Al/Si ratio (0-0.35) and the hierarchical pore structure is realized by Hofmeister anion effects of the Al source itself, [Al(OH)4](-), which change the geometry of CTAB micelles and giant vesicles. The Al is incorporated purely in a tetrahedrally coordinated status, and preliminary results from catalytic experiments show improved acidity of MASS as a catalyst support.