3D porous polymers for selective removal of CO₂ and H₂ storage: experimental and computational studies

In this article, newly designed 3D porous polymers with tuned porosity were synthesized by the polycondensation of tetrakis (4-aminophenyl) methane with pyrrole to form M1 polymer and with phenazine to form M2 polymer. The polymerization reaction used p-formaldehyde as a linker and nitric acid as a catalyst. The newly designed 3D porous polymers showed permanent porosity with a BET surface area of 575 m²/g for M1 and 389 m²/g for M2. The structure and thermal stability were investigated by solid ¹³C-NMR spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, and thermogravimetric analysis (TGA). The performance of the synthesized polymers toward CO₂ and H₂ was evaluated, demonstrating adsorption capacities of 1.85 mmol/g and 2.10 mmol/g for CO₂ by M1 and M2, respectively. The importance of the synthesized polymers lies in their selectivity for CO₂ capture, with CO₂/N₂ selectivity of 43 and 51 for M1 and M2, respectively. M1 and M2 polymers showed their capability for hydrogen storage with a capacity of 66 cm³/g (0.6 wt%) and 87 cm³/g (0.8 wt%), respectively, at 1 bar and 77 K. Molecular dynamics (MD) simulations using the grand canonical Monte Carlo (GCMC) method revealed the presence of considerable microporosity on M2, making it highly selective to CO₂. The exceptional removal capabilities, combined with the high thermal stability and microporosity, enable M2 to be a potential material for flue gas purification and hydrogen storage.