Solvent-free synthesis of amine-grafted adsorbent for direct air capture

Amino-silane-grafted adsorbents were successfully synthesized by a solvent-free method. A silane solution was introduced into the pores of a porous silica support through capillary action and grafted by subsequent heating. Characterization of materials with different synthesis and pre-treatment conditions revealed that the pre-treatment to remove the water in the support and suitable amounts of silane were crucial factors to uniformly graft the amine on the porous support in the solvent-free method. Further, we investigated the CO₂ adsorption performance of amine-grafted materials in dry or humid 400 ppm CO₂ gases, demonstrating that the obtained materials synthesized by the solvent-free method exhibited good adsorption performance, comparable to that of conventional CO₂ adsorbents.