In situ azetidine polymerization elevates the performance of commercial polymer resin sorbents in carbon dioxide...

Commercial, amine-containing porous polymer resins are popular sorbents for CO₂ removal from air, otherwise known as direct air capture (DAC). However, their limited amine density and poor oxidative stability constrain performance. Herein, we introduce a simple one-step method to add additional amine groups onto a commercial resin, such as Lewatit VP OC 1065, by grafting branched poly(propyleneimine) oligomers via in situ acid-catalyzed ring-opening polymerization of azetidine. This "grafting-from" modification strategy enhances the CO₂ capacity by >1.4-fold compared to pristine resin, reaching 1.54 and 3.34 mmol⋅g^-1 under dry DAC (400 ppm CO₂, 30°C) and flue-gas (15% CO₂, 40°C) conditions, respectively. Under humid DAC conditions, the capacity reaches ∼2.5 mmol⋅g^-1 at 25°C and further increases to ∼3.0 mmol⋅g^-1 at -5°C. The optimal sample shows enhanced oxidation resistance under air and maintains improved cycling stability over 150 adsorption-desorption cycles under simulated flue-gas conditions. Overall, this work demonstrates a scalable, versatile strategy to upgrade commercial materials into more efficient and durable sorbents for carbon capture.