Amine-functionalized CNTs@mSiO2 with short radical mesochannels for fast and efficient CO2 capture

Abstract

Amine functionalized adsorbents exhibit significant potential for CO2 capture due to their high efficiency and selectivity. However, their practical application remains constrained by the limited adsorption capacity and slow adsorption kinetics. Herein, we demonstrated an ethylenediamine (ED) functionalized mesoporous silica coated carbon nanotubes (CNTs@mSiO2-ED) composites for fast and efficient CO2 capture. The novel adsorbent was synthesized through a two-step process, consisting of the synthesis of mesoporous silica coated carbon nanotubes (CNTs@mSiO2) as amine carriers via an interfacial self-assembly strategy, followed by amine functionalization using a vapor deposition method. Both the carriers and final adsorbents possess abundant short radical mesochannels, offering direct and ultra-short diffusion paths for amine during functionalism and CO2 for adsorption. As a result, the CNTs@mSiO2-ED adsorbent achieved a maximum CO2 adsorption capacity of 68 mL g-1 (~ 3 mmol g-1, at 298 K, 1 bar) and facile uptake of CO2 reaching a t50 (being the time to achieve 50% of the maximum adsorption capacity) of 1.93 min, 1.70 times higher and 1.32 times faster than for ED-functionalized SBA-15, respectively. This work opens up a new avenue for the design of CO2 adsorption materials to overcome the adsorption and reaction kinetics limitations of other solid porous materials envisaged.