Insights into the Critical Role of Abundant-Porosity Supports in Polyethylenimine Functionalization as Efficient and Stable CO2 Adsorbents

The emerging polyethylenimine (PEI)-functionalized solid adsorbents have witnessed significant development in the implementation of CO2 capture and separation because of their decent adsorption capacity, recyclability, and scalability. As an indispensable substrate, the importance of selecting porous solid supports in PEI functionalization for CO2 adsorption was commonly overlooked in many previous investigations, which instead emphasized screening amine types or developing complex porous materials. To this end, we scrutinized the critical role of different commercial porous supports (silica, alumina, activated carbon, and polymeric resins) in PEI impregnation in this study, taking into account multiple perspectives. Hereinto, the present results identified that abundant larger pore structures and surface functional groups were conducive to loading a considerable amount of PEI molecules. Various supports after PEI functionalization had great differences in adsorption capacities, amine efficiencies, and the corresponding optimal temperatures. In addition, more attention was paid to the role of porous supports in long-term stability during the consecutive adsorption-regeneration cycles, while N-2 and CO2 purging as regeneration strategies, respectively. Especially, CO2-induced degradation due to urea species formation was specifically recognized in a SiO2-based adsorbent, which would induce serious concerns in CO2 cyclic capture. On the other side, we also confirmed that adopting conventional porous supports, for example, HP20, could achieve superior adsorption performance (above 4 mmol CO2/g) and cyclic stability (around 1% loss after 30 cycles) rather than the ones synthesized through complex approaches, which ensured the availability and scalability of PEI-functionalized CO2 adsorbents.

Automated summary

The critical role of different commercial porous supports in PEI impregnation for CO2 adsorption was examined, revealing that supports with abundant larger pore structures and surface functional groups were advantageous for loading PEI molecules. Various supports showed significant differences in adsorption capacities, amine efficiencies, and optimal temperatures after PEI functionalization. Long-term stability during consecutive adsorption-regeneration cycles, with N-2 and CO2 purging as regeneration strategies, was highlighted, and CO2-induced degradation in a SiO2-based adsorbent was specifically recognized. Adoption of conventional porous supports, such as HP20, was confirmed to achieve superior adsorption performance and cyclic stability compared to complex synthesized supports, ensuring availability and scalability of PEI-functionalized CO2 adsorbents.