Surface functionalization of microporous carbon fibers by vapor phase methods for CO2 capture.

The removal of excess CO₂ from the atmosphere is expected to play a major role in the mitigation of global warming. Solid-state adsorbents, consisting of CO₂-binding functionalities on porous supports, can provide high CO₂ capture capacities with low energy requirements. In this contribution, we report on the vapor-phase functionalization of porous carbon fibers with amine functionalities. Functionalization occurs either via direct exposure to cyclic azasilane molecules (2,2-dimethoxy-1,6-diaza-2-silacyclooctane) or by the atomic layer deposition of Al₂O₃ followed by exposure to azasilane. XPS analysis and SEM/energy-dispersive x-ray spectroscopy (EDX) measurements confirmed Al₂O₃ deposition and amine functionalization. Yet, the two different functionalization approaches led to different amine loadings and distinct differences in porosity upon functionalization, which affected CO₂ capture. Combining Al₂O₃ and amine functionalization resulted in fast CO₂ sorption with superior capturing efficiency. In contrast, direct functionalization resulted in strong reduction of the surface area of the porous support and limited gas exchange. We attribute the superior capture efficiency to the porosity level achieved when combining Al₂O₃ and amine functionalization demonstrating that this approach might be valuable for compact high-throughput direct air, CO₂ capture systems. [ABSTRACT FROM AUTHOR]