Metal phosphates have many applications in
catalysis, separation, and proton conduction, but their small surface areas and/or constrained pore structures limit their
utilization. Here, we report two new methods for the liquid-phase grafting of
titanium phosphate onto mesoporous
silica (SBA-15) surfaces: (1) alternate grafting of Ti(OPr(i))(4) and then POCl(3) and (2) one-pot grafting of
titanium phosphate formed in situ by employing Ti(OPr(i))(4) (a base) and POCl(3) (an acid) as an appropriate "acid-base pair". Both the size of mesopores and the content of
titanium phosphate can be changed by increasing the number of modification cycles in a stepwise (or layer-by-layer) fashion. The obtained products were characterized by
inductively coupled plasma optical
emission spectroscopy,
X-ray diffraction, N(2) adsorption-desorption,
transmission electron microscopy, (31)P and (29)Si magic-angle spinning
NMR, and NH(3) temperature-programmed
desorption, and their performance in
acid catalysis and
metal ion adsorption was investigated. This work provides new methodologies for the general synthesis of supported
metal phosphates with large surface areas, ordered nanoporous structures, and acid properties.
