Bi-Component Breakthrough Experiments For The Efficient Direct Air Capture And Water Harvesting

Achieving the European Union’s 2050 climate neutrality goal requires transformative technologies capable of mitigating atmospheric CO₂ concentrations. Direct air capture (DAC) offers a promising pathway toward net-zero emissions and negative emission solutions, but its implementation faces the intrinsic challenge of capturing CO₂ at ultra-dilute concentrations (~420 ppm). While traditional chemisorbents such as amine-based systems exhibit strong CO2 affinity, their high regeneration energy demands and limited stability constrain large-scale deployment. In contrast, recent progress in physical adsorbents, particularly zeolites and metal-organic frameworks (MOFs) has opened new avenues for energy-efficient DAC. This study investigates the physisorption performance of MOR-type zeolites and the fluorinated MOF KAUST-7 (NbOFFIVE-1-Ni) under DAC-relevant conditions. MOR-type zeolites demonstrate high CO₂ uptake (1.15 mmol g-1 at 400 ppm, 30 °C), fast kinetics, and excellent selectivity driven by Na⁺ cation sites within 8-membered ring side pockets, maintaining robust performance even at low temperatures. KAUST-7 achieves benchmark CO2 uptakes (1.3 mmol g-1, 51.4 cm3 (STP) cm-3) through engineered fluorinated channels that enhance CO2 framework interactions, coupled with hydrolytic stability and mild regeneration requirements. However, both materials exhibit significant sensitivity to humidity. To address this, the study explores coupling these CO2-selective adsorbents with a water-harvesting MOF (MIL-160) capable of pre-capturing atmospheric water (Figure1). This approach may simultaneously enhance DAC efficiency and enable water collection in arid environments. The comparative evaluation of these advanced physisorbents highlights their adsorption mechanisms, trade-offs, and scalability potential. The findings provide critical insights into the rational design of next-generation materials for sustainable, large-scale DAC technologies.