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 CO2 uptake capacity of the sorbent but also by the efficiency of adsorption–desorption cycles, which governs the CO2 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 CO2 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 CO2 throughput. This integration of structured sorbent design and process optimization provides a practical framework for realizing highly efficient DAC technologies under realistic operating conditions.