Sub-hour Rapid Cycling of Direct Air Capture Enabled by Engineered Hollow Fiber Sorbents

Solid sorbent direct air capture (DAC) systems are influenced not only by the intrinsic CO 2 uptake capacity of the sorbent but also by the efficiency of adsorption–desorption cycles, which governs the CO 2 capture rate and thus the system productivity. As the system productivity is a key cost driver for DAC, minimizing cycle time through advanced sorbent design and the development of cyclic processes is essential for DAC systems. Here, a rapid temperature swing adsorption (RTSA) process for direct air capture was developed by integrating ethylenediamine-grafted Y zeolite hollow fiber sorbents with a direct contact thermal management strategy. A shell-side water barrier was formed via simple dip coating, enabling direct heat transfer from the fiber surface to the thermal fluid and allowing rapid temperature switching between adsorption at 10 °C and desorption at 90 °C. As a result, temperature transitions were completed within 1 min, and over 97% of the adsorbed CO 2 was recovered in cyclic breakthrough experiments. Through Bayesian optimization (BO), the total cycle time was identified as a key variable affecting DAC productivity, and the present RTSA system experimentally demonstrated that sub-hour cycling maximizes CO 2 throughput. This integration of structured sorbent design and process optimization provides a practical framework for realizing highly efficient DAC technologies under realistic operating conditions.