# Polymeric and Crystalline Materials for Effective and Sustainable CO\({}_{2}\) Capture
## 3 Petroleum-Based Polymers
### Amine-Based Polymers  
Amine-functionalized adsorbents typically consist of porous support to which amines are introduced, either by weak physical adsorption (impregnation) or through strong chemical bonding (grafting/covalent attachment). Impregnated systems involve the direct deposition of amines onto the support, whereas grafted/ covalently bonded systems refer to the chemical incorporation of amines, either during the material's synthesis (in situ) or via post-synthesis modification [116]. Although impregnated CO2 sorbent systems often exhibit high capture capacity, they encounter stability issues such as amine leaching and degradation, as well as limited CO2 transport to active sites due to diffusion hindrance. To overcome these challenges and enhance long-term performance, a grafted/covalently bonded CO2 sorbent systems approach offers improved stability over multiple regeneration cycles. More specifically, polymeric amines, a group of porous materials containing multiple amino groups, are gaining significant attention for improving CO2 capture capacity of supported amine-based sorbent systems due to their higher amine content [116; 117; 118]. It is worth noting that polymeric amines with primary and secondary amine groups are preferred for such applications due to their effectiveness in capturing CO2 in various environmental conditions [119]. For instance, primary amine can efficiently capture CO2 by the formation of stable carbonate species. Secondary amines are considered the ideal functional group (in a polymer porous network) as they give a balance between the adsorption and the regeneration [120]. At last, the tertiary amine can regenerate more easily under mild conditions while being detrimental to the adsorption capacity and selectivity. Polyethylenimine (PEI) is among one of the most utilized and researched polyamines for CO2 capture. Its widespread adoption is due to factors such as its easy availability, high CO2 capture efficiency, elevated amine density, presence of primary amine chain ends, and stability, which enable it to retain CO2 adsorption capability even under elevated temperatures [121]. Figure 2 depicts the main and most reported polymeric amines for CO2 capture. In the same vein, [PERSON] and coworkers recently reported a complete summary encompassing the CO2 uptake performance of several PEI derivatives [117]. In this regard, [PERSON] and coworkers have shown the preparation of a polyvinyl amine (PVAm)/piperazine glycinate membrane for efficient CO2 capture from flue gas [122; 123]. The PVAm polymer was prepared by polymerizing \(N\)-vinyl formamide using AIBA. The obtained polymer was then subjected to acid hydrolysis followed by an ion exchange to generate the PVAm (Figure 3). Optimizing the amine layer thickness, the molecular weight and the piperazine glycinate ratio of the PVAm led to a CO2 permeance up to 1100 GPU. Polymer permeance refers to the ability of a polymeric material to allow substances, typically gases or liquids, to pass through. It is a measure of how easily a specific substance can permeate or diffuse through a polymer film or membrane. Figure 2: Most studied polymeric amines for CO\({}_{2}\) capture. [PERSON] et al. reported the preparation of an impregnated poly(ethyleneimine) (PEI) on a poly(divinylbenzene (PDVB) scaffold [126]. The PDVB support was first prepared by a solvothermal and template-free method using AIBN and DVB in a mixture of THF/H2O. Heating the solution mixture to 120 \({}^{\circ}\)C afforded a PDVB solid scaffold, which was then physically impregnated with PEI at different weight loadings. In terms of CO2 capture, the PEI-PDVB scaffold was able to reach a CO2 capacity of 3.70 mmol g\({}^{-1}\) at 298 K. The authors attributed its performance to its abundant meso-macroropes and large volume pores. [PERSON] and coworkers have reported the direct capture of CO2 from air using a PEI-loaded silica sorbent [127].