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.