Structure refinement of the as-synthesized and the calcined form of zeolite RUB-3 (RTE)

The structure analysis based on single crystal and powder data revealed that the framework structure of RUB-3 (structure type code RTE) consists of small [4(4)5(4)6(2)] building units and medium-large [4(6)5(4)6(6)8(2)] cages with a free volume of ca. 300 Angstrom(3). Interconnected cages form a one-dimensional channel system with narrow, slightly elliptical pore openings (free diameter 3.6 x 4.3 Angstrom(2)). H-1-C-13 CP MAS NMR spectroscopy proved that the cages are occupied by disordered (+/-)-exo-2-aminobicyclo[2.2.1]heptane molecules which were used as templates during the synthesis. The unit cell composition of as-synthesized RUB-3 is (C7H13N2).[Si24O48]. The lattice parameters, bond lengths, bond angles and unit cell volumes are nearly identical for the as-synthesized [a=14.039(2) Angstrom, b=13.602(2) Angstrom, c=7.428 (1) Angstrom, beta=102.22(3)degrees] and calcined form [a=14.018(1) Angstrom, b=13.612(1) Angstrom, c=7.418(1)Angstrom, beta=102.12(1)degrees] of RUB-3. The RTE structure even keeps its symmetry (C2/m) during the calcination process, indicating that the RTE framework topology is very rigid. All crystals are four-fold twins with twin planes {110}. (C) 1998 Elsevier Science B.V. All rights reserved.