The structures of as-synthesized AlPO4-53(A), calcined dehydrated AlPO4-53(B), and AlPO4-53(C), a new phase determined by the FOCUS method

AlPO4-53 was synthesized hydrothermally with methylamine as a structure-directing agent. The structure of as-synthesized AlPO-53(A) was solved using AlPO-EN3 as a starting model. The Rietveld refinement converged (R-p = 0.140) in space group P2(1)2(1)2(1) (a = 10.3212(1) Angstrom, b = 13.6308(1) Angstrom and c = 17.4539(1) Angstrom) for unit cell composition: Al24P24O96. 8.5CH(3)NH(2). 14N(2)O. AlPO-53(A) is isotypic with as-synthesized AlPO-EN3, JDF-2, UiO-12-as, and presumably CFSAPO-1(A). The structure of calcined dehydrated AlPO-53(B) was solved by direct methods, and refined to R-P = 0.084 in Pbca (a = 18.0241(1) Angstrom, b = 13.9174(1) Angstrom and c = 9.6554(1) Angstrom), The topology of AlPO-53(B), the tetrahedral equivalent of AlPO-EN3, is iso-structural with MCS-1 and UiO-12-500. This topology (structure type code AEN) has two 8-ring channels that intersect to form a 2D system. Heating AlPO4-53 to 700 degrees C yields a new condensed phase, AlPO-53(C). The structure of AlPO-53(C) was solved with the FOCUS program and refined to R-P = 0.124 in C121 with a = 16.4440(4) Angstrom, b = 5.1075(1) Angstrom, c = 13.4846(4) Angstrom, and beta = 88.259(1)degrees AlPO-53(C) has a new topology described as brw nets in the ne plane, linked by single and double zigzag chains, parallel to b. The elliptical 8-ring pores, parallel to b, produce a 1D channel system. The highly distorted 4-, 6-, and 8-rings in AlPO-53(B) become more regular in AlPO-53(C). The thermal transformation of AlPO-53(B) to AlPO-53(C) is illustrated. (C) 2000 Elsevier Science B.V. All rights reserved.