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 4⁴5⁴6²] building units and medium–large 4⁶5⁴6⁶8²] cages with a free volume of ca. 300 ų. Interconnected cages form a one-dimensional channel system with narrow, slightly elliptical pore openings (free diameter 3.6×4.3 Ų). ¹H–¹³C CP MAS NMR spectroscopy proved that the cages are occupied by disordered (±)-exo-2-aminobicyclo2.2.1]heptane molecules which were used as templates during the synthesis. The unit cell composition of as-synthesized RUB-3 is (C₇H₁₃N)₂·Si₂₄O₄₈]. The lattice parameters, bond lengths, bond angles and unit cell volumes are nearly identical for the as-synthesized a=14.039(2) Å, b=13.602(2) Å, c=7.428(1) Å, β=102.22(3)°] and calcined form a=14.018(1) Å, b=13.612(1) Å, c=7.418(1) Å, β=102.12(1)°] 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}.