A Comparative Study of a Novel Microporous Indiumphosphate and Other M(III)X(V)O4-Type Microporous Materials

A novel microporous indiumphosphate, InPO4(H2O)2 · 0.1Et3N (InPO4-1) is synthesized from the hydrothermal reaction of H3PO4, In2O3, and H2O in the presence of triethylamine, or n-butylamine, dimethylamine, dipropylamine, ethylenediamine, and tetramethylammonium hydroxide. Single crystal X-ray diffraction studies show that InPO4-1 has orthorhombic symmetry, space group Pbca, with a = 8.842(2) Å, b = 10.1870(10) Å, c = 10.327(2) Å, V = 930.1(3) Å3, and Z = 8. It has a three-dimensional microporous structure with one-dimensional 6- and 4-rings running along the b- and a -axes, respectively. In and P occupy framework positions forming [InO4(H2O)2] octahedral and [PO4] tetrahedral geometry, and they alternate through O bridges. InPO4-1 has poor thermal stability and its microporous structure is comparable to small-pore AlPO4-n. Organic amines that are used in the preparation of InPO4-1 range from primary amine to quaternary ammonia although the mechanism has yet to be understood.