Multifunctional periodic mesoporous benzene-silicas for evaluation of CO₂ adsorption at standard temperature and pressure

Bi-functional periodic mesoporous organosilicas (PMOs) embedded with phenylene- and isocyanurate-bridging groups have been synthesized by a one-pot co-condensation method using 1,4-bis(triethoxysilyl)benzene and tris[3-(trimethoxysilyl)propyl]isocyanurate precursors in the presence of a poly(ethylene oxide)-poly(DL-lactic acid-co-glycolic acid)-poly(ethylene oxide) (PEO-PLGA-PEO) triblock copolymer named LGE54 under acidic conditions. Block copolymer template has been removed by solvent-extraction to get the template-free PMO whereas PLGA block chains from the copolymer template were also removed selectively by thermal treatment at 250 °C retaining PEO chains inside the silica framework. Furthermore, the bi-functional PMO and tri-functional PEO containing PMOs were modified with N-[3-(trimethoxysilyl)propyl]ethylenediamine to prepare amine-coated PMOs on the pore surface. The bi-, tri-, and tetra-functional PMO samples have been thoroughly characterized using small angle X-ray scattering (SAXS) and nitrogen adsorption isotherms to resolve the presence of ordered mesostructure and surface area of the PMOs. Also, solid-state ¹³C- and ²⁹Si CP-MAS NMR studies have been performed to investigate significant chemical linkages from amine-containing modifiers and poly(ethylene oxide) group inside and on the surface of PMO samples. Scanning electron microscopic (SEM), elemental analysis, and thermogravimetric analysis (TGA) have been carried out to obtain the morphology, elemental percentage and thermal stability of the multi-functional PMO samples, respectively. CO₂ capture has been investigated on multi-functional PMO samples at 25 °C and 1 atm using a mixed flow by 3:2 vol ratio of CO₂ and N₂ gas. Amine-functionalized PMO has shown significantly higher amount of CO₂ uptake than those obtained using PMO itself and the respective PMOs modified with different functionalities.