A NOVEL MONOCLINIC ALPO4-SODALITE FORMED IN THE PRESENCE OF DIMETHYLFORMAMIDE AS TEMPLATE AND SOLVENT

A new microporous aluminophosphate was obtained in a quasi-non-aqueous system using dimethylformamide (DMF) as solvent and templating agent. The limited amount of water is responsible for the slow hydrolysis of the Al source, yielding sodalite cages stabilized by DMF templates. T he new phase has monoclinic symmetry and space group Cc. The structure of the monoclinic AlPO4-SOD is close to the sodalite structure type, with a framework composed of [4(6)6(8)] cages. The unit cell parameter s are, respectively, a = 12.94 Angstrom, b = 12.47 Angstrom, c = 8.63 Angstrom and beta = 95.77 degrees. All the phosphorus atoms are tetrac oordinated, while aluminum atoms show both tetrahedral and octahedral coordination. Upon heating, the monoclinic AlPO4-SOD is converted into AlPO4-20, which has cubic SOD topology. The bonding scheme involving water and dimethylformamide molecules linked to hexacoordinated Al ato ms of the monoclinic AlPO4-SOD framework is destroyed, yielding a more relaxed cubic network. (C) 1998 Elsevier Science B.V. All rights rese rved.