Ion-Exchange Resin-Templated Carbon Capture Sorbents with Hierarchical Pores

Abstract

The pore structure of mesoporous silica is crucial to its application as a substrate for CO₂ capture sorbents. In this work, the synthesis of resin-templated silica, a new class of hierarchically meso-/macroporous silica for fabrication of CO₂ capture sorbents, was reported. Unlike the conventional acid-catalyzed synthesis of mesoporous silica using self-assembled surfactant or block copolymer templates, the resin-templated silica is derived from porous ion-exchange resin templates using a catalyst-free method that involves three simple steps of silane soaking, moisture exposure, and air calcination. The resin-templated silica reproduced the spherical shape of the porous ion-exchange resin template. It was also found that pores in resin templates were crucial to creating mesoporosity in resin-templated silica. The resin-templated silica has simultaneous attractive surface area and pore volume, which were both substantially higher than those of the ion-exchange resin template. Impregnation of the mesopores and macropores by polymeric amine provided novel amine-oxide sorbents for CO₂ capture, that is, resin-templated sorbents. The resin-templated sorbents impregnated using a 15 wt % polyethylenimine (PEI)/methanol solution showed competitive direct air capture (at 400 ppm) performance with a CO₂ sorption capacity of 2.1 mmol of CO₂/g of SiO₂ and amine efficiency of 0.11 mol of CO₂/mol of N at an amine loading of 0.83 g of PEI/g of SiO₂.