Amine-Functionalized Branched Polyamides for Reversible CO ₂ Capture

Rapid industrialization and deforestation are major causes of the increase in carbon dioxide (CO2) levels in the atmosphere. New methods to capture and recover CO2 efficiently from the environment are needed to make chemicals or reduce the atmospheric concentration. A hyperbranched polymer should provide more cavity space and functional groups than a linear polymer, thereby improving CO2 capture efficiency. Here, we report two structurally different hyperbranched polyaramides (PAs) for CO2 capture and recovery. The PA-based adsorbents were surface-modified with polyethylenimine (PEI) and fully characterized to establish the surface area, lattice structure, and adsorption properties. Raman spectroscopy was used to quantify the CO2 adsorption and desorption on the PA surface. PEI-functionalized PAs showed a high CO2 adsorption capacity (7.913 mmol/g) due to the presence of amide and amine functional groups on the surface of a network structure. Multiple factors, such as strong hydrogen bonds between dipolar CO2 molecules and amide (−CONH−) groups, the branching of the polymer chains, and the presence of amine groups from PEI on the surface, influenced the adsorption of CO2 from the environment. It is interesting to observe the highly reversible adsorption and desorption of CO2 molecules on the surfaces of modified solid PAs. Such stable, surface-modified PAs are good candidates for capturing CO2 gas from industrial emission ducts and enriching it for further usage.