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

Abstract

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.