Quaternized Graphene for High-Performance Moisture Swing Direct Air Capture of CO₂

Nowadays, moisture-swing adsorption technology still relies on quaternary ammonium resins with limited CO₂ capacity under ambient air conditions. In this work, a groundbreaking moisture-driven sorbent is developed starting from commercial graphene flakes and using glycidyltrimethylammonium chloride for incorporation of CO₂-sensitive quaternary ammonium functional groups. Boasting an outstanding CO₂ capture performance under ultra-diluted conditions (namely, 3.24 mmol g^-1 at CO₂ 400 ppm and 20% RH), the functionalized sorbent (fGO) features clear competitive advantages over current technologies for direct air capture. Notably, fGO demonstrated unprecedented moisture-swing capacity, ease of regenerability, versatility, selectivity, and longevity. These distinctive features position the fGO as an advanced and promising solution, showcasing its potential to outperform existing methods for moisture-swing direct air capture of CO₂.