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 their limited adsorption capacity and slow adsorption kinetics. Herein, we demonstrated an ethylenediamine (ED)-functionalized mesoporous silica-coated carbon nanotube (CNTs@mSiO₂-ED) composite for fast and efficient CO₂ capture. The novel adsorbent was synthesized through a two-step process involving 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 amines during functionalization 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, 298 K, 1 bar) and the facile uptake of CO₂, reaching a t₅₀ (the time to achieve 50% of the maximum adsorption capacity) of 1.93 min, 1.70 times higher and 1.32 times shorter than those of 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.