Ultra-high capacity quaternized PET for moisture-swing CO₂ capture from air

Direct air capture (DAC) of CO₂ is pivotal for mitigating climate change, with moisture-swing adsorbents emerging as an energy-efficient approach to this end. Herein, we report ultra-high capacity quaternized polyethylene terephthalate (QPET) adsorbents fabricated via ultraviolet-induced grafting of quaternary ammonium groups onto PET substrates. The resulting QPET fabric exhibits a remarkably high adsorption capacity of 6.08 mmol/g under ambient conditions, which is 1.64 times that the prior record (3.71 mmol/g) for moisture-swing adsorbents, and is over 6 times that of the most-studied resin-based adsorbents. This exceptional performance is attributed to the high density of grafted quaternary ammonium groups and the intrinsic three-dimensional fibrous network of the PET fabric substrate, which provide abundant CO₂ adsorption sites and gas diffusion channels. The adsorbent demonstrates excellent cyclic stability, retaining consistent adsorption/desorption capacities across three full cycles and ten short-term cycles. Furthermore, its moisture-driven regeneration mechanism obviates the need for thermal or pressure inputs, while the utilization of low-cost PET substrates enhances scalability. This work provides a promising strategy for developing high-performance, cost-effective adsorbents tailored for large-scale CO₂ capture from ambient air.