Scalable metal-organic frameworks for efficient low concentration CO₂ capture under humid flue gas conditions

The global energy supply still largely relies on fossil fuels, whose combustion releases significant amounts of carbon dioxide (CO₂), the primary anthropogenic greenhouse gas linked to climate change. Adsorption on solid porous materials offers a promising alternative to conventional amine-based systems for CO₂ capture from industrial flue gases. While various materials, including zeolites and metal-organic frameworks (MOFs), have been extensively studied for high-concentration CO₂ streams, post-combustion capture at low concentrations (below 5% CO₂) under realistic conditions with water vapor remains poorly explored. Material selection requires balancing CO₂ adsorption capacity against water affinity, as strong hydrophilicity deteriorates regeneration efficiency. The challenge is to identify scalable, environmentally friendly materials that maintain high CO₂ selectivity under realistic flue gas conditions containing both low CO₂ concentrations and significant water vapor. Here, we show that CALF-20, a scalable MOF, exhibits superior CO₂ adsorption selectivity and regenerability compared to other tested materials, both in dry and humid conditions. Under dynamic breakthrough conditions using 2.5% CO₂ and 50% relative humidity, CALF-20 maintained a high CO₂ uptake (1.49 mmol g^-1) consistent with static isotherm data, and demonstrated complete regenerability at 80 °C without loss of performance over multiple cycles. These results directly contrast with hydrophilic zeolites, which, despite high raw CO₂ capacities, are unsuitable under realistic, humid flue gas. Our results under industrially relevant post-combustion conditions demonstrate that low water affinity combined with moderate CO₂ capacity outperforms high-capacity hydrophilic materials. This approach represents an effective pathway for CO₂ capture under realistic conditions and provides valuable insights for the development of selective, robust, and scalable CO₂ adsorbents. Such developments are expected to contribute significantly to reducing atmospheric CO₂ emissions and addressing climate change mitigation targets in the coming years.