Adjustable Functionalization of Hyper-Cross-Linked Polymers of Intrinsic Microporosity for Enhanced CO₂ Adsorption and Selectivity over N₂ and CH₄

Abstract

In this paper, we report the design, synthesis, and characterization of a series of hyper-cross-linked polymers of intrinsic microporosity (PIMs), with high CO 2 uptake and good CO 2 /N 2 and CO 2 /CH 4 selectivity, which makes them competitive for carbon capture and biogas upgrading. The starting hydrocarbon polymers' backbones were functionalized with groups such as −NO 2 , −NH 2 , and −HSO 3 , with the aim of tuning their adsorption selectivity toward CO 2 over nitrogen and methane. This led to a significant improvement in the performance in the potential separation of these gases. All polymers were characterized via Fourier transform infrared (FTIR) spectroscopy and 13 C solid-state NMR to confirm their molecular structures and isothermal gas adsorption to assess their porosity, pore size distribution, and selectivity. The insertion of the functional groups resulted in an overall decrease in the porosity of the starting polymers, which was compensated with an improvement in the final CO 2 uptake and selectivity over the chosen gases. The best uptakes were achieved with the sulfonated polymers, which reached up to 298 mg g −1 (6.77 mmol g −1 ), whereas the best CO 2 /N 2 selectivities were recorded by the aminated polymers, which reached 26.5. Regarding CH 4 , the most interesting selectivities over CO 2 were also obtained with the aminated PIMs, with values up to 8.6. The reason for the improvements was ascribed to a synergetic contribution of porosity, choice of the functional group, and optimal isosteric heat of adsorption of the materials.

Polymers of Intrinsic Microporosity─Molecular Mobility and Physical Aging Revisited by Dielectric Spectroscopy and X-ray Scattering

“…The addition of nanoparticles will reduce the free interface and therefore retard physical aging. Alternatively, also approaches optimizing the chemical architecture have been pursued (see, for instance, refs – ). However, up to now, an effective long-term suppression of physical aging has not been achieved. , This is probably in part also due to an incomplete understanding of the molecular mobility-related phenomena in such high-free volume polymers compared to conventional ones.…”

CO2 Separation by Imide/Imine Organic Cages

“…Comparison of the curves derived from the isothermal gas adsorption measurements at 298 K for CO 2 , N 2 and CH 4 , provides interesting insight into the potential use of these materials for post‐combustion separation (Figure 6). [53] The amount of CO 2 adsorbed largely exceeds the amount of N 2 . Even just visually, we can expect C2 having a better selectivity than C1 , but the calculation for a possible post‐combustion separation cannot be done simply looking at the final uptake of the two gases at 1 bar.…”

Amine-functionalized porous organic polymers for carbon dioxide capture

“…119 Similar to other sorbents, the amine groups have been incorporated in HCPs by direct amine synthesis, [120][121][122][123] amine grafting 106,124,125 and amine impregnation. 126,127 Fayemiwo et al investigated a series of amine-functionalized HCPs (HCP-MAAMs) for low-pressure CO 2 capture such as from coal-fired power plant flue gas. 94 The synthesis of HCPs is based on the co-polymerization of methacrylamide (MAAM) and ethylene glycol dimethacrylate (EGDMA) using azobisisobutyronitrile (AIBN) as an initiator (Fig.…”

“…119 Similar to other sorbents, the amine groups have been incorporated in HCPs by direct amine synthesis, 120–123 amine grafting 106,124,125 and amine impregnation. 126,127…”