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

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