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Polybenzimidazole (PBI) with a strong size-sieving ability exhibits attractive H2/CO2 separation properties for blue H2 production and CO2 capture. Herein, we report that PBI can be facilely cross-linked with polycarboxylic acids, oxalic acid (OA), and trans-aconitic acid (TaA) to improve its separation performance. The acids react with the amines on the PBI chains, decreasing free volume and increasing size-sieving ability. The acid doping increases H2/CO2 selectivity from 12 to as high as 45 at 35 °C. The acid-doped samples demonstrate stable H2/CO2 separation performance when challenged with simulated syngas containing water vapor at 150 °C, which surpasses state-of-the-art polymers and Robeson's upper bound for H2/CO2 separation.

Controlling the microstructure of heterogeneous, polymer membranes used in gas barrier and gas separation technologies is challenging. Being able to control composite structures is beneficial to achieve an optimum combination of gas permeation and mechanical performance. In addition, unique properties such as anisotropy and confined transport can be controlled by tailoring the size and position of constituent materials. Two-stage reactive polymer (TSRP) networks are an emerging dual-cure polymer material for spatially varying cross-linking density via photopatterning. In this work a thiol–acrylate-based TSRP was used to investigate the effects of pattern geometry on CO₂ permeability and mechanical properties. Line and square patterns of alternating high and low cross-linking density, with characteristic dimension between 1 mm and 10 μm, were generated in TSRP membranes. Notably, synergistic enhanced barrier properties were observed for 10 μm square patterns of lower cross-linking density (or higher permeability) material exhibiting two confined dimensions compared to line gratings with only one confined dimension.

An ionic liquid (IL) [P66614][Triz] with a low regeneration temperature was loaded on a graphene nanoplatelet (GNP) and reduced graphene oxide (RGO) to accelerate the CO2 absorption rate. High-resolution transmission electron microscopy (HRTEM) patterns showed that GNP was composed of a regular “honeycomb” lattice, but a regular lattice structure was not observed for RGO as a result of the functional group on it. The CO2 absorption capacity (63.6 mg of CO2/g of IL) and absorption peak rate (22.4 mg of CO2 g–1 of IL min–1) of IL loaded on GNP were increased by 8.2 and 72.3%, respectively, compared to those of neat IL. The supported IL performed better because [P66614][Triz] was oriented in a favorable dispersion as a result of the negative ζ potential of the GNP surface. In contrast, the CO2 absorption rate of RGO–20% IL (mass ratio of RGO/IL = 4:1) was lower than that of IL, which could be attributed to the hydrogen bond between surface oxygen functional groups and IL. 13C nuclear magnetic resonance and M...

A phase-change solvent for CO2 absorption was prepared by mixing N-methyl-1,3-diaminopropane (MAPA) and N,N-dimethylformamide (DMF). In this MAPA/DMF solvent, MAPA-carbamate precipitate was formed after CO2 absorption to facilitate reducing energy consumption of amine regeneration. The CO2 uptake of MAPA/DMF solvent (14.8 mg/g solvent) was increased by 22% compared with that of MAPA/water solvent (12.1 mg/g solvent). For MAPA/DMF solvent, time was reduced by 22% to reach the CO2 absorption equilibrium. The maximum CO2 uptake rate of MAPA/DMF solvent was 30% higher than that of MAPA/water solvent because DMF displayed higher CO2 solubility and lower MAPA-carbamate solubility than water. Differential scanning calorimetry and thermogravimetry experiments revealed that MAPA(H+)2 and MAPA(CO2–)2 compositions in MAPA-carbamate precipitate first decomposed (peak temperature = 59.9 °C). Subsequently, the MAPACO2 compositions in precipitate also decomposed (peak temperature = 124.2 °C).

With the upgrading of fermentative biogas to produce gaseous transport fuel, ionic liquid (IL) [P66614][2-Op], which adsorbed CO2 through multiple-site cooperative interactions, was loaded onto molecular sieve MCM-41 to adsorb CO2 in a biohythane atmosphere (CH4 + H2 + CO2). [P66614][2-Op] loaded onto MCM-41 exhibited a higher CO2 adsorption rate than pure IL during the initial stage because of its larger reaction surface area. However, the CO2 adsorption rate of [P66614][2-Op] loaded onto MCM-41 became lower than that of pure IL as the reaction continued because CO2 was inaccessible to the IL blocked within the inner pores of MCM-41. The CO2 adsorption rate of IL loaded onto the molecular sieve (MCM-41–50% IL) was (51.5 mg of CO2 g–1 of IL min–1) 2.1 times higher than that of pure IL during the initial 1 min in a pure CO2 atmosphere and was (24.6 mg of CO2 g–1 of IL min–1) 2.2 times higher than that of pure IL during the initial 2 min in a biohythane atmosphere.