Structural and chemical studies of zeolite ABW type phases : Syntheses and characterizations of an ammonium zincophosphate and an ammonium beryllophosphate zeolite ABW structure

Hydrothermal syntheses and X-ray crystal structures of two framework phosphates are described. The framework topologies of NH4ZnPO4 and NH4BePO4 are the same as that of the zeolite ABW type. Preparation of these two compounds is a rare example of the direct synthesis of ammonium zeolite analog structures. The framework can be considered as built from the stacking of hexagonal layers. A literature study of ABCX4-type structures reveals more than two dozen compounds with the ABW-type topology in addition to about a dozen structures already tabulated. The newly discovered materials with the ABW topology have diverse chemical compositions and display various lattice symmetries. Other interesting properties of these ABW phases include displacive phase transitions and crystal twinning. The compositional and structural diversities of these ABW phases have important implications for the future design of new zeolite phases. Crystal data for NH4ZnPOa: M = 178.38, space group P21(No. 4), a = 8.7966(5)Å, b = 5.4565(3)A, c = 8.9654(5)Å, β = 90.323(1)°, V= 430.75(1)Å3, Z = 4, Dc = 2.753 g cm-3, MoKα, μ = 5.970 mm-1, 2θmax = 56.00°, R(F) = 3.88% for 129 parameters and 1769 reflections with l > 2σ(l). Crystal data for NH4BePO4: M = 122.02, space group Pna2, (No. 33), a = 8.7196(7)Å, b = 8.5919(7)A, c = 4.9661(4)Å, V = 372.05(5)Å3, Z = 4, Dc = 2.178 g cm-3, MoKα, μ = 0.608 mm-1, 2θmax = 56.46°, R(F) = 2.77% for 81 parameters and 840 reflections with l > 2σ(l).