Solvent-free porous liquids for CO2 capture based on silica nanoparticles with different core structures

Abstract

Type I porous liquids (PLs) containing porosity are promising candidates for gas sorption and separation, homogeneous catalysis, and so forth. In this research, large porous silica nanoparticles (PSNs) and hollow wormhole silica nanoparticles (HSNs) are reported to fabricate Type I PLs through a facile synthetic strategy, where polyether amine is linked to nanoparticles by the silane coupling agent for CO2 capture. Experimental results showed that canopies endow PSNs and HSNs with excellent fluidity along with the thermal stability of PLs at high temperature. The CO2 sorption capability and dispersion stability were profoundly influenced by the specific surface area and pore size of PLs cores. At 25 °C and 2 bar, the CO2 sorption capacities of pure M2070, PL_1_M2070, PL_2_M2070, and PL_3_M2070 were 10.9317 cm3/g, 9.1295 cm3/g, 6.2504 cm3/g, and 5.3518 cm3/g, respectively. Results showed that CO2 sorption capability of porous silica nanoparticle assisted PLs with a large specific surface area and small pore sizes was superior. If the pore size was large enough, canopy would enter and fill the pores of silica nanoparticles, preventing part pores and polyether amine from offering active CO2 sorption sites, thereby minimizing the CO2 sorption and affecting the stability of the PLs. Sorption kinetics fitting results showed that the CO2 sorption of PLs was the combination of physical dissolution and chemisorption. Furthermore, the adsorption capacity of PL_1_M2070 was 90.5% of the original CO2 adsorption capacity after 10 adsorption/desorption cycles, indicating excellent recyclability.