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

In this work, we report a new route to improve the CO 2 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 CO 2 adsorbents. Silanol-rich silicas grafted with BPEI exhibited 70% higher amine density and 47% higher CO 2 adsorption capacity than its calcined counterpart. The adsorbent achieved a maximum CO 2 adsorption efficiency up to 13.82 mmol CO 2 /g-BPEI. Adsorbed species found in the infrared spectra suggested that silanols may contribute to the enhanced CO 2 adsorption efficiency on grafted amines. Silanol-rich silica functionalized with BPEI retained more porosity than its calcined counterparts, which may account for its superior CO 2 adsorption capacity. Silanol-rich silica impregnated with amines achieved the highest CO 2 adsorption efficiency ever reported (5.65 mmol/g, 526.7 mg/g-BPEI). Adsorption kinetic modeling confirmed that silanol-rich adsorbent provides better CO 2 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 CO 2 capture.