Mesoporous AlPO4 Glass from a Simple Aqueous Sol–Gel Route

Abstract

Transparent and colorless AlPO4 gel and glass are prepared via a simple aqueous sol–gel route using aluminum lactate and phosphoric acid as precursors. The stoichiometric AlPO4 glass derived from this sol–gel route has a mesoporous structure with a surface area of 504 m2/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, 27Al MAS NMR spectra indicate that aluminum is almost completely converted into AlO4 units. 27Al{31P} rotational echo double resonance and 31P{27Al} rotational echo adiabatic passage double resonance NMR experiments as well as 27Al and 31P MAS NMR results further confirm that the prepared AlPO4 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 AlPO4.