New insights into the encapsulation and stabilization of heteropolyacids inside the pore walls of mesostructured silica materials

A method of synthesizing stable and reactive modified mesoporous hybrid materials with intact heteropolyacid (HPA) Keggin units is reported. The materials were synthesized by a one-pot method using a mixture of structure directing agents (CTAB and Pluronic 123). The key to obtaining stable HPA containing materials was the sequential calcination and extraction steps, and the authors present a working hypothesis for this phenomenon. Studies of several other key factors concerning synthetic parameters are also reported. All materials were characterized by a wide variety of physical and spectroscopic methods at each step of the synthesis. The kinetics of the esterification of acetic acid by butanol mediated by several of the materials and relevant homogeneous acid catalysts showed that the HPA containing hybrid material was a highly effective catalyst.