Mesoporous AlPO4 Glass from a Simple Aqueous Sol–Gel Route

Transparent and colorless AlPO 4 gel and glass are prepared via a simple aqueous sol-gel route using aluminum lactate and phosphoric acid as precursors. The stoichiometric AlPO 4 glass derived from this sol-gel route has a mesoporous structure with a surface area of 504 m 2 /g after calcination to 600°C. With increasing gel-to-glass processing temperature, the average degree of P/Al connectivity increases. After sample calcination at 600°C for 4 h, 27 Al MAS NMR spectra indicate that aluminum is almost completely converted into AlO 4 units. 27 Al{ 31 P} rotational echo double resonance and 31 P{ 27 Al} rotational echo adiabatic passage double resonance NMR experiments as well as 27 Al and 31 P MAS NMR results further confirm that the prepared AlPO 4 glass has a three-dimensional network based on alternating Al(OP) 4 and P(OAl) 4 tetrahedral units in analogy to the local structure of crystalline AlPO 4 .