A new facile method for synthesis of porous azo-linked polymers (ALPs) is reported. The synthesis of ALPs was accomplished by homocoupling of aniline-like building units in the presence of copper(I) bromide and pyridine. The resulting ALPs exhibit high surface areas (SABET = 862–1235 m2 g–1), high physiochemical stability, and considerable gas storage capacity especially at high-pressure settings. Under low pressure conditions, ALPs have remarkable CO2 uptake (up to 5.37 mmol g–1 at 273 K and 1 bar), as well as moderate CO2/N2 (29–43) and CO2/CH4 (6–8) selectivity. Low pressure gas uptake experiments were used to calculate the binding affinities of small gas molecules and revealed that ALPs have high heats of adsorption for hydrogen (7.5–8 kJ mol–1), methane (18–21 kJ mol–1), and carbon dioxide (28–30 kJ mol–1). Under high pressure conditions, the best performing polymer, ALP-1, stores significant amounts of H2 (24 g L–1, 77 K/70 bar), CH4 (67 g L–1, 298 K/70 bar), and CO2 (304 g L–1, 298 K/40 bar).

Hole-some mixture: A 2D mesoporous covalent organic framework (see figure) featuring expanded pyrene cores and linked by imine linkages has a high surface area (SA(BET) = 2723 m(2)  g(-1)) and exhibits significant gas storage capacities under high pressure, which make this class of material very promising for gas storage applications.

Heteroatom-doped porous carbons are emerging as platforms for use in a wide range of applications including catalysis, energy storage, and gas separation or storage, among others. The use of high activation temperatures and heteroatom multiple-source precursors remain great challenges, and this study aims to addresses both issues. A series of highly porous N-doped carbon (CPC) materials was successfully synthesized by chemical activation of benzimidazole-linked polymers (BILPs) followed by thermolysis under argon. The high temperature synthesized CPC-700 reaches surface area and pore volume as high as 3240 m2 g–1 and 1.51 cm3 g–1, respectively, while low temperature activated CPC-550 exhibits the highest ultramicropore volume of 0.35 cm3 g–1. The controlled activation process endows CPCs with diverse textural properties, adjustable nitrogen content (1–8 wt %), and remarkable gas sorption properties. In particular, exceptionally high CO2 uptake capacities of 5.8 mmol g–1 (1.0 bar) and 2.1 mmol g–1 (0.15 bar) at ambient temperature were obtained for materials prepared at 550 °C due to a combination of a high level of N-doping and ultramicroporosity. Furthermore, CPCs prepared at higher temperatures exhibit remarkable total uptake for CO2 (25.7 mmol g–1 at 298 K and 30 bar) and CH4 (20.5 mmol g–1 at 298 K and 65 bar) as a result of higher total micropores and small mesopores volume. Interestingly, the N sites within the imidazole rings of BILPs are intrinsically located in pyrrolic/pyridinic positions typically found in N-doped carbons. Therefore, the chemical and physical transformation of BILPs into CPCs is thermodynamically favored and saves significant amounts of energy that would otherwise be consumed during carbonization processes.

Triazine-based benzimidazole-linked polymers (TBILPs), TBILP-1 and TBILP-2, were synthesized by condensation reaction of 2,4,6-tris(4-formylphenyl)-1,3,5-triazine (TFPT) with 1,2,4,5-benzenetetraamine tetrachloride (BTA) and 2,3,6,7,14,15-hexaaminotriptycene (HATT), respectively. The Ar sorption isotherms at 87 K revealed high surface areas for TBILP-1 (330 m 2 g −1 ) and TBILP-2 (1080 m 2 g −1 ). TBILP-2 adsorbed significantly high CO 2 (5.19 mmol g −1 /228 mg g −1 ) at 1 bar and 273 K. Initial slope selectivity calculations demonstrated that TBILP-1 has very high selectivity for CO 2 over N 2 (63) at 298 K, outperforming all triazine-based porous organic polymers reported to date. On the other hand, the larger surface area of TBILP-2 leads to relatively lower selectivity for CO 2 /N 2 (40) and CO 2 /CH 4 (7) at 298 K. TBILPs showed moderate isosteric heats of adsorption for CO 2 : TBILP-1 (35 kJ mol −1 ) and TBILP-2 (29 kJ mol −1 ) enabling high and reversible CO 2 uptake at ambient temperature. In addition, TBILPs displayed promising working capacity, regenerability, and sorbent selection parameter values for CO 2 capture from gas mixtures under vacuum swing adsorption (VSA) and pressure swing adsorption (PSA) conditions.

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