Interlayer Expansion of the Layered Zeolite Precursor RUB-39: A Universal Method To Synthesize Functionalized Microporous Silicates

摘要

Interlayer expansion reaction leads to a new family of microporous framework silicates using hydrous layer silicates as precursors. Using silylating agents such as dichlor-dimethylsilane (DCDMS), neighboring layers connect. In addition to the topotactic condensation of hydrous silicates, this leads to expanded silicate frameworks, with the number of pore openings increased by two Si-units. The hydrous layer silicate RUB-39 has been subjected to interlayer expansion reaction, using DCDMS at 180 °C, yielding new, crystalline microporous frameworks (COE-1 and COE-2), varying in their methyl function carrying as-made and oxidized calcined forms, respectively. An intersecting two-dimensional (2D) channel system with 10- and 12-membered rings is accessible for probe molecules, leading to a surface area of 540 m /g and a pore volume of 0.169 cm /g. The powder diagram was indexedin space group P2 with α = 15.609(3) A, b = 11.163(1) A, c= 7.30l(l) A,and β = 91.2(l)°forCOE-l anda = 15.594(4) A,b- 11.039(2) A, c = 7.276(1) A, and β = 91.2(1)° for calcined COE-2. Rietveld refinement of the powder X-ray diflractometry (PXRD) diagram confirmed the framework topology for COE-1 and COE-2 (χ~2 = 8.0 and 9.9, respectively) and showed that the silicate framework suffers from stacking disorder after interlayer expansion reaction. DIFFaX simulations allowed for the modeling of the stacking disorder, showing that RRO- and HEU-type stacking occurs.