Porous aromatic organosilicates: surface chemistry


  Martin Kejik,^1 Julius Gabelis,^2 Zdenek Moravec,^1 Craig E. Barnes,^3 Aivaras Kareiva,^2 Jiri
                                             Pinkas^1

^1Masaryk University, Czech Republic, ^2 Vilnius University, Lithuania,^ 3 University of Tennessee,
                                                USA

                                       jpinkas@chemi.muni.cz


Recently we have developed highly porous hybrid organosilicate materials via non-hydrolytic sol-gel
methods. Silicon(IV) acetate and tris(acetoxy)silane are readily attacked by multifunctional
nucleophilic building blocks such as 1,3,5-trihydroxybenzene resulting in formation of amorphous
micro/mesoporous gels. As acetic acid is the only byproduct, removal of all volatiles in vacuo
affords pure xerogels and the degree of condensation can thus be monitored by gravimetry. Both
products have thermal stability up to 400–500 °C with BET surface areas of 990 and 933 m^2 g^-1 for
silicon(IV) acetate and tris(acetoxy)silane, respectively. The product of tris(acetoxy)silane also
possesses exceptionally high total pore volume of 1.36 cm^3 g^-1. As both materials are amorphous
imperfect alignment of building units limits the degree of condensation to 85–90 % and the surface
therefore contains residual acetate and phenolic hydroxyl functional groups.


Herein we report a study on the chemistry of the surface groups and their reactions with alcohols,
phenol and silylating reagents (Me[3]SiCl, (Me[3]Si)[2]NH) in post-synthetic treatments. The
investigation focuses on the control of surface hydrophobicity, acidity and coordination
properties. Products were characterized by elemental analyses, solid-state ^13C and ^29Si NMR, IR
spectroscopy, nitrogen adsorption analysis, thermal analysis TG/DSC, and XRD measurements.


This research has been financially supported by the Ministry of Education, Youth and Sports of the
Czech Republic under the project CEITEC 2020 (LQ1601).