Porous organic polymers containing nitrogen-rich building units are among the most promising materials for selective CO2 capture and separation which can have a tangible impact on the environment and clean energy applications. Herein we report on the synthesis and characterization of four new porous benzimidazole-linked polymers (BILPs) and evaluate their performance in small gas storage (H2, CH4, CO2) and selective CO2 binding over N2 and CH4. BILPs were synthesized in good yields by the condensation reaction between aryl-o-diamine and aryl-aldehyde building blocks. The resulting BILPs exhibit moderate surface area (SABET = 599–1306 m2 g–1), high chemical and thermal stability, and remarkable gas uptake and selectivity. The highest selectivity based on initial slope calculations at 273 K was observed for BILP-2: CO2/N2 (113) and CO2/CH4 (17), while the highest storage capacity was recorded for BILP-4: CO2 (24 wt % at 273 K and 1 bar) and H2 (2.3 wt % at 77 K and 1 bar). These selectivities and gas uptakes are among the highest by porous organic polymers known to date which in addition to the remarkable chemical and physical stability of BILPs make this class of material very promising for future use in gas storage and separation applications.

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).

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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.

Successful incorporation of triptycene into benzimidazole-linked polymers leads to the highest CO(2) uptake (5.12 mmol g(-1), 273 K and 1 bar) by porous organic polymers and results in high CO(2)/N(2) (63) and CO(2)/CH(4) (8.4) selectivities.

Porous organic polymers containing nitrogen-rich building units are among the most promising materials for selective CO 2 capture and separation applications that impact the environment and the quality of methane and hydrogen fuels. In this study, we report on post-synthesis modification of nanoporous organic frameworks (NPOFs) and its impact on gas storage (H 2 , CH 4 , CO 2 ) and selective CO 2 binding over N 2 and CH 4 under ambient conditions. The synthesis of NPOF-4 was accomplished via acid catalyzed cyclotrimerization reaction of 1,3,5,7-tetrakis(4-acetylphenyl)adamantane in ethanol/xylenes. NPOF-4 is microporous and has high surface area (SA BET ¼ 1249 m 2 g À1 ). Post-synthesis modification of NPOF-4 by nitration afforded NPOF-4-NO 2 and its subsequent reduction resulted in an aminefunctionalized framework NPOF-4-NH 2 that exhibits improved gas storage capacities and very high CO 2 /N 2 (139) and CO 2 /CH 4 (15) selectivities compared to NPOF-4.

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The synthesis of highly porous borazine-linked polymers (BLPs) and their gas uptakes are reported. BLPs exhibit high surface areas up to 2866 m 2 g À1 and can store significant amounts of H 2 (1.93 wt%) and CO 2 (12.8 wt%) at 77 K and 273 K, respectively at 1.0 bar with respective isosteric heats of adsorption of 6.0 and 25.2 kJ mol À1 .Recently there has been great interest in the design and synthesis of highly porous organic architectures due to their multifaceted potential use in applications that include storage, separation, conductivity, and catalysis. 1 The chemical composition, physical and textural properties are dictated during synthesis that allow for materials with enhanced properties relevant to their respective applications. With the exception of microcrystalline covalent-organic frameworks (COFs), 2,3 these polymeric materials are amorphous yet can possess considerable porosity and well-defined cavities which render them highly attractive especially in adsorptive gas storage. 4 Such desirable traits are imparted into organic materials through the use of rigid building blocks that direct the growth of polymer networks without the aid of templating agents. [1][2][3] In addition to customized porosity, polymerization processes can lead to pore wall functionalization that significantly enhance gas uptake and selectivity as we have demonstrated recently for benzimidazole-linked polymers. 5 Alternative methods for improved gas uptake (i.e. hydrogen) by porous architectures can also be accessed by the use of polarizable building units that increase hydrogen-framework interactions. 6 Along this line, we sought after the inclusion of borazine (B 3 N 3 ) as a functionalized and polarizable building block into porous organic polymers. 7 Borazine is isostructural to the boroxine units found in COFs prepared by boronic acid self-condensation reactions 2 and has been mainly used for the fabrication of BN-based ceramics or in organic optoelectronics. [8][9][10] However, up to date, the use of borazine for the preparation of porous polymers for gas storage remains fairly undeveloped.We report herein on the synthesis and characterization of a new class of highly porous borazine-linked polymers and investigate their performance in gas (H 2 , CO 2 , CH 4 ) storage application under low pressure and cryogenic conditions. The synthesis of BLP-1(H) and Scheme 1 Synthesis of BLP-1(H) and BLP-12(H) from in situ thermal decomposition of arylamine-borane adducts.