Microporous hyper-cross-linked aromatic polymers designed for methane and carbon dioxide adsorption

A Friedel-Crafts reaction was used to obtain covalent aromatic networks with high surface area and microporosity suited for CO₂ and CH₄ adsorption, even at low pressures. Starting from tetraphenylmethane and formaldehyde dimethyl acetal in different concentrations, the reaction yields porous polymers which were characterized with a wealth of experimental and computational methods. Thermogravimetry, infrared spectroscopy, and solid-state NMR were used to study the material structure. The pore distributions were measured by applying nonlocal density functional theory analysis to the adsorption isotherms of N₂ at 77 K and Ar at 87 K (the latter being more suited for pore widths less than 10 Å). Carbon dioxide and methane were adsorbed at 273 and 298 K to evaluate the performance of these systems in gas capture, separation, and storage. A theoretical model of the porous network was defined to describe the ordered fraction of the material, with particular attention to ultramicropores. Ar, CO₂, and CH₄ adsorption in this model material was simulated by Monte Carlo techniques with a purposely optimized force field.