Amine-bridged periodic mesoporous organosilica adsorbents for CO2 capture

Abstract

Novel periodic mesoporous organosilica (PMOs) were synthesized using different commercial non-aminated and aminated bisilanes in order to incorporate aminated sites within the silica walls. Three different commercial bisilanes were employed: i)without amine groups, ii)with one amine group, and iii)with two amine groups. Moreover, materials were prepared with different molar ratios of non-aminated and aminated bisilanes. P123 was used as structure directing agent for the mesoporosity. The amino functional groups of the PMOs so prepared were incorporated within the silica walls of the obtained solid particles. Moreover, for comparative purposes, BEBA-0, that is a non-aminated PMO, was functionalized via grafting with N1-(3-trimethoxysilylpropyl)diethylenetriamine (DT) and impregnation with polyethyleneimine (PEI) to produce amino functionalized materials. All these materials were tested for CO2 capture through CO2 adsorption/desorption isotherms and TGA studies. It was observed that increasing the concentration of amine containing bisilane increased the CO2 capture capacity significantly from 21.4 mg/g to 47.3 mg/g. The PMO synthesized with the bisilane containing two amine groups had higher CO2 uptake than the one containing one amine group from 47.3 to 62.6 mg/g due to the presence of more functional groups in the final material (6.0 versus 9.4% wt N, respectively). The cyclic capacity of the adsorbents via a series of adsorption/desorption tests has also been determined, the results showing the low reactivity decay (less than 3%) of the novel PMOs and materials prepared by grafting during the first 10 cycles, when compared with the 13% of PEI-impregnated material.