Interlayer Expansion of the Hydrous Layer Silicate RUB-36 to a Functionalized, Microporous Framework Silicate: Crystal Structure Analysis and Physical and Chemical Characterization

The hydrous layer silicate RUB-36, (C₆H₁₆N)₄ [H₄Si₃₆O₇₆], has been used for an interlayer expansion reaction with dichlorodimethylsilane to interconnect neighboring ferrierite-type layers to a three-dimensional framework silicate. The linker group (−O–Si­(CH₃)₂–O−) still has the two methyl groups in the as-synthesized form (material name COE-3 [Si₂₀O₃₈(CH₃)₄] for the silicate framework) rendering hydrophobic properties. The interlayer expanded zeolite, IEZ, is thermally stable and can be calcined at 550 °C to yield a hydrophilic material COE-4 [Si₂₀O₃₈(OH)₄]. ²⁹Si solid state MAS NMR experiments confirm the insertion of the linker group and the methyl and hydroxyl substitution in the as-made and calcined form, respectively. The BET surface area is 238 m²/g for COE-3 and 350 m²/g for COE-4. COE-3 and COE-4 crystallize in space group Pm with a = 12.2503(3) Å, b = 13.9752(2) Å, c = 7.3850(1) Å, and β = 107.33(1)° and a = 12.16985(4) Å, b = 13.95066(3) Å, c = 7.37058(2) Å, and β = 107.30(1)°, respectively. Rietveld crystal structure refinement of the PXRD pattern of COE-3 and COE-4 reveal the expanded, two-dimensional 10-ring pore system including the linker group as homogeneous structural property of the materials.