Surface functionalization of mesoporous silica SBA-15 by liquid-phase grafting of zirconium phosphate

The introduction of mesoporous silicas in the 1990s has offered new opportunities for the engineering of ordered catalytic nanoreactors, but the acid properties of mesoporous silicas are rather poor. Herein, mesoporous silica (SBA-15) surfaces were functionalized by zirconium phosphate via two methods recently developed in our group. Zr(OPr)4 and POCl3 were used as appropriate precursors in both methods. The main difference between these methods lies in whether Zr(OPr)4 is grafted onto SBA-15 first and POCl3 second (method 1) or the grafting process takes place in one pot, with SBA-15, Zr(OPr)4, and POCl3 altogether (method 2). More zirconium phosphate could be grafted by repeating the above procedures. The materials were characterized by ICP-OES, XRD, N2 adsorption–desorption, TEM, 31P and 29Si MAS NMR, and NH3-TPD, and their applications in catalytic isopropanol dehydration, cumene cracking, and metal-ion adsorption were demonstrated. Aluminum phosphate-modified SBA-15 samples could be obtained via these two methods as well. This work enriches the family of metal phosphate-functionalized mesoporous silicas as new solid acid catalysts.