Direct CO₂ Capture from Air using Poly(ethylenimine)-Loaded Polymer/Silica Fiber Sorbents

Direct CO 2 capture from atmospheric air is gaining increased attention as one of the most scalable negative carbon approaches available to tackle climate change if coupled with the sequestration of CO 2 geologically. Furthermore, it can also provide CO 2 for further utilization from a globally uniform source, which is especially advantageous for economies without natural sources of carbon-based feedstocks. Solid-supported amine-based materials are effective for direct air capture (DAC) due to their high CO 2 uptakes and acceptable sorption kinetics at ambient temperature. In this work, we describe the application of polymer/silica fiber sorbents functionalized with a primary amine-rich polymer, poly(ethylenimine) (PEI), for DAC. Monolithic fiber sorbents composed of cellulose acetate and SiO 2 are synthesized via the dry-jet, wet quench spinning technique. These fibers are then functionalized with PEI ( M w 800 Da) in a simple and scalable postspinning infusion step and tested for CO 2 capture under pseudoequilibrium conditions as well as under breakthrough conditions. An investigation to study the effect of feed flow rate, adsorption temperature, and presence of moisture in the feed on the CO 2 breakthrough performance of a densely packed fiber sorbent module is conducted to highlight the potential application of this class of structured contactors in direct air capture. The pressure drop of these contactors at high gas velocities is also evaluated. Finally, a vacuum-assisted desorption step is demonstrated for production of high-purity CO 2 from both dry and humid ambient air mixtures.