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

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. [ABSTRACT FROM AUTHOR]