(278a) Hierarchically Meso-/Macroporous Resin-Templated Sorbents

Direct air capture is among the negative emissions technologies to slow the increasing atmospheric CO₂ concentration and global temperature rise. Direct air capture can rely on liquid solvents, solid sorbents, or electrochemical approaches. Notably, the strong amine-CO₂ reaction provided by amine-oxide sorbents can allow selective CO₂ capture from ultra-dilute (~420ppm CO₂) ambient air. Amine-oxide sorbents are traditionally made by impregnation of polymeric amines in porous oxide substrates such as ordered mesoporous silica, which are synthesized by soft templating methods using self-assembly of silica species and micelles of cationic surfactants or block copolymers. Development of low-cost porous oxide substrates is crucial to large-scale deployment of amine-oxide sorbents for direct air capture.

In this talk, we will present novel resin-templated sorbents for direct air capture. The resin-templated sorbents were made by impregnating polymeric amines into resin-templated silica, a novel class of low-cost hierarchically porous meso-/macroporous silica. The resin-templated silica was fabricated using inexpensive ion-exchange resin templates through a catalyst/surfactant-free petrification process, which is distinct from the traditional ordered mesoporous silica fabrication process using self-assembly surfactants or copolymers. The petrification process involved three simple steps: silane soaking, moisture exposure, and air calcination. The resin-templated silica retained the spherical shape of the resin templates with reduced diameter. While the resin template had low surface area below 50 m²/g, the resin-templated silica had much higher surface area of 650 m²/g. At amine loading of 0.83g amine/g silica, the resin-templated sorbent showed CO₂ sorption capacity of 2.1 mmol CO₂/g silica for 400ppm CO₂ feed, which was highly competitive with traditional amine-oxide sorbents at comparable amine loading. To our best knowledge, this was the first time that ion-exchange resins were used as templates to fabricate porous oxides and to derive CO₂ capture sorbents. The work not only demonstrates a potential new application of ion-exchange resins, but also opens the door to a new class of hierarchically porous materials for CO₂ capture and beyond.