Pseudomorphic transformation and post synthetic modification of amorphous silica for CO2 sorption applications

Abstract

Template directed porous silica has shown significant promise in numerous applications such as gas sorption, catalysis and pharmaceutical drug delivery. Mesoporous silicas such as MCM-41, SBA-15 and KIT-6 have been widely reported; however, thus far these materials require long synthesis processes and expensive starting materials. As an alternative, pseudomorphic transformations can convert low-grade amorphous silica into more useful materials. Herein, we demonstrate the effect of pseudomorphic transformations upon the properties of non-porous silica spheres. Surface area can be increased from < 2 m2 g−1, for non-porous silica spheres, to 724 m2 g−1 for the resulting pseudomorphic species. Silica species were subsequently functionalised with aminopropyltriethoxysilane (APTES) and tetraethylenepentamine (TEPA) via post-synthetic modification. Post-synthetic modification was found to significantly enhance the CO2 sorption performance of the silica species with CO2 sorption capacities of up to ca. 92 mg CO2 g−1 achieved, compared to a maximum uptake of 18 mg CO2 g−1 for the non-porous silica variants.