Molecule-level Design to Form Pocket Structures for Improving Amine Efficiency in CO2 Capture

Solid amine adsorbents represent a promising class of CO 2 sorbents, but their amine efficiency is limited by the inaccessibility of peripheral amines. The surface of mesocellular silica foam (MCF) is functionalized with the mixture of short-chain 3-Glycidyloxypropyl) triethoxysilane (GPTES) and long-chain Octadecyltrimethoxysilane (OTMS), forming pocket structures on the support surface, thereby exposing more amine sites and enhancing the amine efficiency of polyethylenimine (PEI). The resulting adsorbent demonstrates a high CO 2 adsorption capacity (5.02 mmol g −1 at 50 °C, 10 vol.% CO 2 , and 50%RH), high amine efficiency (0.43 at the dry condition), outstanding cyclic stability (0.5% performance decline per cycle under the conditions of dry CO 2 regeneration), and fast adsorption kinetics (15 min for adsorption saturation at 50 °C). First-principles calculations and CO 2 temperature-programmed desorption (TPD) experiments demonstrate that the introduction of GPTES and OTMS is beneficial to decreasing adsorption energy and forming paired carbamic acid states and ammonium carbamate states.