Comparative characteristics of texture and properties of hybrid organic–inorganic adsorbents functionalized by amine and thiol groups

摘要

The structure and texture characteristics of the hybrid organic–inorganic adsorbents, which were obtained by using of two-component systems of “structure-forming agent/trifunctional silane”, are compared as follows: the first component is Si(OC2H5)4 or (C2H5O)3Si–A–Si(OC2H5)3, where A = –(CH2)2– or –C6H4–; the second one is alkoxysilane with amine (–NH2, NH, –NH(CH2)2NH2) and thiol (–SH) groups. The adsorbents, derived from TEOS, have more accessible functional groups (2.6–4.2 mmol/g) than xerogels, which are based on bis(triethoxysilanes) (1.0–2.6 mmol/g). On another hand xerogels derived from bis(triethoxysilanes) have a more extended porous structure (Ssp =516–968 m2/g, Vs = 0.418–1.490 cm3/g, d = 2.5–15.0 nm) than those that are based on TEOS (Ssp = 4–631 m2/g, Vs = 0.005–1.382 cm3/g, d = 2.3–17.7 nm). The geometric dimensions of functional groups have a more essential effect on the parameters of porous structure in the case of TEOS-derived xerogels. Using solid-state NMR spectroscopy, it has been shown that in synthesis of xerogels with the use of TEOS, the molecular frame of globules is formed by structural units Qn (n = 2,3,4), and the functional groups exist as structural units of Tn (n = 2,3). The xerogels obtained with using bis(triethoxysilanes) consist only of structural units of Tn-type (n = 1,2,3).