Aminopolymer Confined in Ethane‐Silica Nanotubes for CO₂ Capture from Ambient Air

Abstract Direct air capture as the only way for reducing current CO₂ concentration in air is very challenging, however, due to the low CO₂ concentration (ca. 400 ppm). Herein, we reported an efficient adsorbent for CO₂ capture, which was prepared by the encapsulation of polyethylenimine (PEI) in ethane‐silica nanotubes with diameter less than 10 nm. Compared with bulk mesoporous silicas/ethane‐silicas, the PEI tends to be highly dispersed in the nanotubes due to the co‐existence of both tubular channels and intervoid space. Consequently, the PEI encapsulated in nanotubes showed much higher N efficiency (0.22 mol CO₂/mol N at 30 °C and 0.1 bar) and CO₂ uptake capacity than that encapsulated in the bulk mesoporous silicas. It was also observed that the dispersed PEI not directly interacted with the pore wall, afforded high N efficiency. Results of the breakthrough experiments using simulated air (400 ppm CO₂/N₂) showed that PEI encapsulated in nanotubes with CO₂ uptake capacity of 1.0 mmol/g, fast equilibrium time and high stability are promising for CO₂ capture from air.