Nitrogen-rich conjugated microporous polymers: impact of building blocks on porosity and gas adsorption

Abstract

Nitrogen-rich conjugated microporous polymers have been synthesized via palladium-catalyzed Suzuki cross-coupling or Sonogashira polycondensation from diamino-grafted or azo-fused monomers. These polymers are stable in various solvents and are thermally stable. The surface area, pore size and morphology of the resulting polymers are closely related to the building blocks, and the azo-fused polymers with rigid conformation show an enhanced surface area up to 1146 m² g⁻¹ compared with the diamino-grafted polymers. Azo-CMP1 with the highest surface area among the polymers shows a remarkable CO₂ uptake of 3.72 mmol g⁻¹ (1.13 bar and 273 K) with a good CO₂/N₂ selectivity of 42.1 : 1 at 273 K. All of the polymers show high isosteric heats of CO₂ adsorption (∼30 kJ mol⁻¹) because the incorporation of nitrogen atoms into the skeleton of the conjugated microporous polymers enhanced the interaction between the pore wall and CO₂ molecules. Due to the high surface area, good physicochemical stability and outstanding CO₂ sorption performances, these nitrogen-rich polymer networks are promising candidates for potential applications in post-combustion CO₂ capture and sequestration technology.