Epoxide-Functionalized, Poly(ethylenimine)-Confined Silica/Polymer Module Affording Sustainable CO₂ Capture in Rapid Thermal Swing Adsorption

Creating a module that achieves sustainable CO₂ capture while being compatible with the existing industry is paramount in overcoming the current CO₂-driven environmental issues. This paper presents the fabrication of hollow fiber sorbents (HFSs) and their respective modules to capture CO₂ by the rapid thermal swing adsorption process (RTSA). Poly(amide-imide) (PAI)/microspheric SiO₂ composites were fabricated with a so-called "sieve-in-a-cage" microarchitecture which promotes CO₂ diffusion. More importantly, a selected amount of 1,2-epoxybutane (EB)-functionalized poly(ethylenimine) (PEI), denoted as 0.37EB-PEI, was incorporated into our PAI/SiO₂ composites forming PAI/SiO₂/0.37EB-PEI HFSs which enhanced the thermal stability with a moderate CO₂ sorption uptake of 0.88 mmol CO₂ g^-1. The resulting HFSs were assembled into a module using either stainless steel (SS) or poly(tetrafluoroethylene) (PTFE), and their respective CO₂-capturing performances in the RTSA process were compared. The two modules had a comparable breakthrough CO₂ capacity of 0.42 mmol CO₂ g^-1 for a wet feed mixture of CO₂/He/N₂ (14 mol/14 mol/72 mol) (RH 100%) and a comparable CO₂ desorption efficiency (i.e., 95% desorption within 2 min) under 100% CO₂ at 120 °C due to the presence of the 0.37EB-PEI; however, different thermal properties inherent to the modular materials caused the PTFE-based module to outperform the SS-based counterpart in terms of cooling, enabling the execution of an entire RTSA cycle within 8 min. Additionally, the PAI/SiO₂/0.37EB-PEI/PTFE module maintained its breakthrough capacity of 0.42 mmol CO₂ g^-1 over five consecutive RTSA cycles, confirming its good long-term stability as well.