2. Capture of CO₂ from Concentrated Sources and the Atmosphere

As the rapid rise of the atmospheric CO₂ concentration has aroused increasing concern worldwide on the global climate change, the research activities in CO₂ capture both from the concentrated CO₂ sources and the atmosphere have grown significantly. The amine based solid sorbents exhibited great promise in the near-future application for CO₂ capture owing to their advantages including high CO₂ capacity even at extremely low CO₂ concentration (e.g., 400 ppm), excellent CO₂ sorption selectivity, no need for moisture pre-removal (moisture even shows promotion effect), lower energy consumption, less corrosion and easy handling compared to liquid amine. Among them, PEI-based sorbents have been considered as one of most promising candidates and have been extensively studied. Great progress has been made in the past two decades. Hence, in this review, we summarize the recent advances with supported PEI sorbents for CO₂ capture, with an emphasis on (1) sorbent material development including the effects of support and polymer structure; (2) CO₂ sorption mechanism; (3) CO₂ sorption kinetics, (4) sorbent deactivation, and (5) practical implementation of PEI-based sorbent materials. At last, the remaining problems and challenges that need to be addressed to improve the competitiveness of sorbent-based capture technologies are discussed. Through the current review, we expect it will not only offer a summary on the recent progress on the supported PEI sorbents, but also provide possible links between fundamental studies and practical applications.