Synthesis and characterization of two galliophosphates with occluded methylamine

Abstract

Two novel framework galliophosphates have been synthesized from ethylene glycol solvent in the presence of a template, methylamine, by varying the content of the amine in reaction mixtures. The X-ray powder diffraction pattern of one crystalline phase is indexable on the basis of an orthorhombic cell having a= 16.2818 ± 0.0018 Å, b= 9.7343 ± 0.0013 Å and c= 8.8040 ± 0.0013 Å; the other has an orthorhombic cell with a= 10.2500 ± 0.0019 Å, b= 14.1107 ± 0.0014 Å and c= 16.9308 ± 0.0027 Å. Chemical analysis, combined with experimental density and indexed X-ray powder diffraction data, discloses their idealized formulae to be Ga₃P₃O₁₂(CH₃NH₂)₂(H₂O) with Z= 4 and D= 2.73 g cm^–3, and Ga₃P₃O₁₂(CH₃NH₂)(H₂O) with Z= 8 and D= 2.94 g cm^–3, respectively. Ga₃P₃O₁₂(CH₃NH₂)(H₂O) has poor thermal stability; loss of methylamine and water destroys its framework structure. However, the Ga₃P₃O₁₂(CH₃NH₂)₂(H₂O) precursor is converted into the molecular sieve GaPO₄–25 upon calcination above 280 °C.