Silanol-rich platelet silica modified with branched amine for efficient CO2 capture

Abstract

In this work, we report a new route to improve the CO2 adsorption performance of solid amine adsorbents. Platelet mesoporous silicas with abundant surface silanols were prepared by emulsion synthesis followed by simple solvent extraction. These silanol-rich silica particles were then functionalized with branched polyethyleneimine (BPEI) by grafting or impregnation to prepare CO2 adsorbents. Silanol-rich silicas grafted with BPEI exhibited 70% higher amine density and 47% higher CO2 adsorption capacity than its calcined counterpart. The adsorbent achieved a maximum CO2 adsorption efficiency up to 13.82 mmol CO2/g-BPEI. Adsorbed species found in the infrared spectra suggested that silanols may contribute to the enhanced CO2 adsorption efficiency on grafted amines. Silanol-rich silica functionalized with BPEI retained more porosity than its calcined counterparts, which may account for its superior CO2 adsorption capacity. Silanol-rich silica impregnated with amines achieved the highest CO2 adsorption efficiency ever reported (5.65 mmol/g, 526.7 mg/g-BPEI). Adsorption kinetic modeling confirmed that silanol-rich adsorbent provides better CO2 diffusion pathways. These potential benefits of silanol-amine interaction, coupled with platelet mesoporous structure and branched polyamine chains, opens a new pathway to high-performance adsorbents for CO2 capture.