Highly Selective Capture of the Greenhouse Gas CO₂ in Polymers

Owing to their high physicochemical stability and low skeleton density, polymers are highly promising for capturing the greenhouse gas CO₂. However, complicated monomers, expensive catalysts, and/or severe conditions are usually required for their synthesis, which makes the process costly, tedious, and hard to scale up. In this paper, a facile nucleophilic substitution reaction is developed to synthesize polymers from low-cost monomers, namely chloromethylbenzene and various diamines. Due to the appropriate reactivity of monomers, the polymerization takes place at a low temperature of about 60°C in the absence of any catalysts. A series of polymers containing plentiful secondary amines are successfully fabricated; these secondary amines provide a proper adsorbate-adsorbent interaction from the viewpoints of selective capture of CO₂ and energy-efficient regeneration of adsorbents. Moreover, the materials possess well-defined micropores with the dimension close to the size of adsorbate molecules and subsequently, exhibit the molecule sieving effect. As a result, these materials are active in selective adsorption of CO₂ and show high CO₂/N₂ and CO₂/CH₄ selectivities. More importantly, the adsorbents can be completely regenerated under mild conditions, and no loss in activity is detected after eight cycles.