# Polymeric and Crystalline Materials for Effective and Sustainable CO\({}_{2}\) Capture
## 3 Petroleum-Based Polymers
### Porous Organic Polymers
reported a mesoporous \(o\)-hydroxyazobenzene polymer for CO\({}_{2}\) capture and conversion [162]. The polymers were prepared via a diazo coupling reaction of aryl tri/diamine with tri/diphenol in an aqueous solution at 0-5 \({}^{\circ}\)C leading to HAzo-POP compounds showing a CO\({}_{2}\) adsorption capacity of 1.68 mmol g\({}^{-1}\) at 273 K and 1 bar (Figure 7). Figure 7: Examples of porous, nanoporous, and microporous organic polymers [154, 159, 165, 164, 165]. [PERSON] and coworkers have reported the preparation of a benzimidazole-based material (BILB-101) as an efficient ultra-microporous organic polymer [161] (Figure 7). In terms of synthesis, the latter was prepared by a simple and efficient polycondensation reaction between the 1,2,4,5-benzenetetramine and 1,3,5-triformylbenzene. A CO\({}_{2}\) uptake of around 1 mmol g\({}^{-1}\) (4 wt %) at 298 K and 0.15 bars was reported for this material as well as an exceptional CO\({}_{2}\)/N\({}_{2}\) selectivity. Benzoxazine-based porous organic polymers were reported recently by [PERSON] et al. [166]. They prepared the benzoxazine (BZ) unit through a sequence of steps by first reacting triphenylamine (TPA) and dihydroxy terephthalaldehyde (DHPT) units, followed by a Sonogashira-Hagihara coupling reaction between BZ monomers functionalized with TPA and DHTP was carried out to give the resulting polymer poly(DHTP-Ea BZ) (Figure 8). The BZ monomers were prepared using a multistep process that involved Schiff base formation, reduction, and Mannich reactions. A CO\({}_{2}\) capture capacity of 3.29 mmol g\({}^{-1}\) at 298 K and 1 bar was recorded. [PERSON] et al. have reported a crown ether benzozazine-linked porous polymer [167]. In particular, they synthesized the CE-BZ monomer by a Schiff-base formation in the presence of 4-bromosalicylaldehyde, followed by a reduction in NaBH\({}_{4}\) and a Mannich condensation with formaldehyde in dioxane/water to furnish the targeted monomer. The polymer (CE-BZ-TPE-POP) was obtained by a Sonogashira-Hagihara Pd cross-coupling reaction in the presence of a copper catalyst and tetrapheylethylene (Figure 8). In terms of CO\({}_{2}\) capture capacity, an uptake of 4.39 mmol g\({}^{-1}\) (298 K, 1 bar) was obtained after thermal polymerization at high temperature (200-300 \({}^{\circ}\)C). \(N\)-heterocyclic carbenes (NHC) have been reported as CO\({}_{2}\) capture materials [168]. The \(N\)-heterocyclic carbenes were prepared in a three-step synthesis. First, a reaction of tetraphenylmethane incorporating 2,6-diisopropyl aniline with glyoxal gave the bis(2,6-diisopropyl phenyl)diazbutadiene. Second, the latter was reacted with paraformaldehyde in the presence of HCl to yield the corresponding imidazolium chloride derivative. Third, the NHC intermediate is obtained upon the neutralization of the imidazolium chloride with potassium _tert_-butoxide furnishing the NP-NHC (Figure 9). It is important to note that the isopropyl moieties were effective for steric confinement, leading to reduced stability of the NP-NHC-CO\({}_{2}\) adduct. This facilitates the efficient release of captured CO\({}_{2}\) at elevated temperatures and concurrently enhances its catalytic activity in the CO\({}_{2}\) conversion process. CO\({}_{2}\) capture capacity was found to be 0.78 mmol g\({}^{-1}\) at 298 K and 1 bar. Finally, the NP-NHC substrate also demonstrated a cycloaddition of CO\({}_{2}\) to epoxide capability for selected substrates only (i.e., 2-methyloxirane, 2-(chloromethyl)oxirane, and 2-butyloxirane). Interestingly, [PERSON] et al. reported an \(N\)-doped porous carbon from a polymer precursor based on triazole moeity [169]. Concerning the synthetic route, the 2,4,6-tris(bromomethyl) mesitylene and 3,5-diamino-1,2,4-triazole were reacted in tetrahydrofuran, at 62 \({}^{\circ}\)C without the use of any catalysts under a N\({}_{2}\) atmosphere according to a nucleophilic substitution reaction affording polymer NUT-21. Then, a carbonization step (KOH, then 500 \({}^{\circ}\)C, 600 \({}^{\circ}\)C,  
Figure 8: Benzoxazine-based polymers [166; 167].