Hybrid microporous and mesoporous organosilicate covalent polymers with high porosity

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Authors

KEJÍK Martin MORAVEC Zdeněk BARNES Craig E PINKAS Jiří

Type Article in Periodical
Magazine / Source MICROPOROUS AND MESOPOROUS MATERIALS
MU Faculty or unit

Faculty of Science

Citation
Doi http://dx.doi.org/10.1016/j.micromeso.2016.11.012
Field Inorganic chemistry
Keywords Sol-gel; Non-hydrolytic condensation; Acetic acid elimination; Microporous; Mesoporous; Hybrid; Organosilicates
Description A novel non-hydrolytic sol-gel synthesis of hybrid organosilicates is reported allowing control of micro/mesoporous character of the xerogels by variation of the silicon precursor. The polycondensation reaction of silicon(IV) acetate, Si(OAc)(4), with 1,3,5-trihydroxybenzene (THB) in dry dioxane at 100 degrees C produces acetic acid and highly porous amorphous aromatic organosilicate xerogels. Their apparent BET surface areas are as high as 990 m(2) g(-1) and the total pore volume is 0.843 cm(3) g-1. These materials are mostly microporous with a low abundance of mesopores and an average pore size of 3.5 nm. The reaction of HSi(OAc)(3) with THB produced a novel mesoporous material with properties superior to xerogels obtained from Si(OAc)(4). The BET surface area of 933 m(2) g(-1) is retained upon heating and average pore size reached 6.0 nm. The total pore volume of 1.36 cm(3) g(-1) is the highest value achieved in porous aromatic organosilicates so far and is comparable to values typical for 3D covalent organic networks (COFs). The materials are stable up to 400-500 degrees C but they are sensitive to hydrolysis in moist air. The reactions of other silicon precursors (MeSi(OAc)(3) and (BuSi)-Bu-t(OAc)(3)) and larger polyphenol connectors, 1,3,5-tris(4 '-hydroxyphenyl)benzene (THPB), 2,4,6-tris(4 '-hydroxyphenyl)-1,3,5-triazine (THPTA), and 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP), produced materials with less satisfactory properties. (C) 2016 Elsevier Inc. All rights reserved.
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