Post-synthetic hydrothermal treatment in NH₄OH solution containing cetyltrimethylammonium bromide.

Silica sodalite was obtained using topotactic conversion of layered silicate RUB-15 through stepwise processes that consisted of the control of stacking sequence of the layers, interlayer condensation by refluxing, and elimination of intercalated guest species. The interlayer condensation of RUB-15, in which acetic acid was pre-intercalated between the layers to control the stacking sequence, afforded a sodalite framework containing organic guest species by refluxing in N-methylformamide (NMF). The pre-intercalated acetic acid molecules were largely replaced with NMF. This formation process of silica sodalite containing large amounts of intercalated organic guest species is in clear contrast to the previously reported process that used direct calcination of an intercalation compound of layered RUB-15 accommodating acetic acid between the layers. Calcination of the condensed product provided sodalite with fewer defects than the directly calcined product, thus indicating the advantage of the stepwise process. The method reported here is useful for the preparation of pure silica sodalite with relatively low defects and plate-like morphology.

Interlayer silylation of layered sodium octosilicate (Na-Oct) with various organoalkoxysilanes was conducted using hexadecyltrimethylammonium ion-exchanged layered octosilicate (C 16 TMA-Oct) as an intermediate in the presence or absence of tetrabutylammonium fluoride (TBAF). The degree of silylation was increased by adding TBAF. It is suggested that F À ions perform a nucleophilic attack on the alkoxysilanes, which promotes the silylation reaction. C 16 TMA-Oct was silylated with octyltriethoxysilane (C 8 TES) or 3-mercaptopropyltriethoxysilane (MPTES) to compare the reactivity of the two organoalkoxysilanes in the presence or absence of TBAF. A higher degree of silylation of C 16 TMA-Oct was observed with MPTES, suggesting the higher accessibility of this silylating agent into the interlayer polar region of C 16 TMA-Oct. Overall TBAF appears as a relevant catalyst for the covalent interlayer surface modification of layered silicates with organic functional groups.

Silicate nanoscrolls with crystalline walls were prepared by intercalation of layered octosilicate with organoammonium ions and the subsequent solvothermal treatment.