Post-Synthesis Stabilization of Germanosilicate Zeolites ITH, IWW, and UTL by Substitution of Ge for Al.

Germanosilicate zeolites often suffer from low hydrothermal stability due to the high content of Ge. Herein, we investigated the post-synthesis introduction of Al accompanied by stabilization of selected germanosilicates by degermanation/alumination treatments. The influence of chemical composition and topology of parent germanosilicate zeolites (ITH, IWW, and UTL) on the post-synthesis incorporation of Al was studied. Alumination of ITH (Si/Ge=2-13) and IWW (Si/Ge=3-7) zeolites resulted in the partial substitution of Ge for Al (up to 80 %), which was enhanced with a decrease of Ge content in the parent zeolite. In contrast, in extra-large pore zeolite UTL (Si/Ge=4-6) the hydrolysis of the interlayer Ge-O bonds dominated over substitution. The stabilization of zeolite UTL was achieved using a novel two-step degermanation/alumination procedure by the partial post-synthesis substitution of Ge for Si followed by alumination. This new method of stabilization and incorporation of strong acid sites may extend the utilization of germanosilicate zeolites, which has been until now been limited.

Fabrication of Hybrid Organic-Inorganic Materials with Tunable Porosity for Catalytic Application.

Novel layered organic-inorganic materials functionalized with amino groups have been synthesized by using a two-dimensional zeolitic precursor, IPC-1P, prepared by a top-down approach from zeolite UTL. The formation of porous materials containing silsesquioxane linkers covalently bonded to zeolite layers in the interlayer space was confirmed by a variety of characterization techniques (N2  sorption, XRD, TEM). The textural properties and catalytic behavior of functionalized hybrid materials synthesized by direct pillaring of IPC-1P or by grafting of (3-aminopropyl)silyl groups to the IPC-1P precursor preliminarily pillared with tetraethoxysilane (TEOS) were compared. The use of a mixture of aminosilsesquioxanes and TEOS for pillaring of IPC-1P led to the formation of functionalized materials, which are characterized by excellent textural properties (SBET =154-435 m2 g-1 , Vtotal =0.336-0.630 cm3 g-1 ) and provide a 100 % yield of target benzylidenemalononitrile in the Knoevenagel condensation of benzaldehyde and malononitrile.