Monte Carlo Modeling of Carbon Dioxide Adsorption in Porous Aromatic Frameworks

Abstract

The adsorption isotherms of CO2 in several porous aromatic frameworks (PAFs) have been simulated with Grand Canonical Monte Carlo technique, to support the synthesis of new materials for efficient carbon dioxide capture and storage. The simulations covered the 0-60 bar pressure range and were repeated at 273, 298, and 323 K. The force field employed in the simulations was optimized to fit the correct behavior of the free gas and to reproduce the CO2-phenyl interactions computed at high quantum mechanical level. PAFs are based on the diamond structure, with polyaromatic chains inserted in C-C bonds. We examined four PAF-30n (n being the number of phenyl rings in the aromatic linkers), finding that PAF-302 is overall the best performing, although PAF-301 provides higher adsorbed densities at very low pressure. The CO2 adsorption then was simulated in a number of modified PAF-302, with different functional groups (aminomethane, toluene, pyridine, and imidazole) attached to the phenyl chains; different degrees of substitution (25%, 50%, and 100% derivatized rings) were considered. The effects of functionalization and the dependence on the substitution degree are carefully discussed, to determine the most promising materials at low, intermediate, and high pressures.

Microporous Hyper-Cross-Linked Aromatic Polymers Designed for Methane and Carbon Dioxide Adsorption

“…However, in quantitative 13 C solid state MAS NMR spectra ( Figure S2) this signal is under the limit of detectability: the chloromethyl carbon peak is found at very low intensity confirming that a small amount of these groups is formed during side reactions. Noteworthy, the resonances due to methylene carbons are broadened either due to the non-averaging of 13 C- 35,37 Cl residual dipolar couplings (as in -CH2Cl) or due to the heterogeneous broadening associated with an extensive distribution of chemical shifts (as in Ph-CH2-Ph) 29 . 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 Powder X-ray diffraction ( Figure S3) confirms the formation of amorphous materials, as expected for crosslinked polymers, with only two broad signals at 2Θ ~15°-20° and 43°, related to direct ring-ring interactions, which are favored by the intrinsic flexibility of the polymeric structure 44 .…”

On the Gas Storage Properties of 3D Porous Carbons Derived from Hyper-Crosslinked Polymers

“…Microporous materials, such as activated carbons (ACs) [15,16,17,18,19], zeolites, silicas, porous organic-inorganic hybrid frameworks [20,21,22], and porous organic polymer networks [23,24,25], are excellent candidates for these applications. Among the porous organic systems, the Porous Aromatic Framework (PAF) family has received great attention recently [26,27,28], thanks to their exceptional stability and their very high surface area; in particular, PAF-302 (also called PAF-1 in the literature) exhibits one of the highest BET surface areas reported so far, along with a high affinity for methane [29,30,31], and to a certain extent, for CO 2 [32,33,34,35,36].…”

An atomistic model of a disordered nanoporous solid: Interplay between Monte Carlo simulations and gas adsorption experiments

“…This model, referred to as mPAF-FCL, was easily prepared starting from the periodic structure of PAF-301, 30,36,53 i. e. a diamond network with a phenyl ring inserted in each CC bond: every two tetracoordinated carbons, two phenyl rings were replaced by hydrogen atoms as illustrated in Figure 2, and the structure was optimized by CRYSTAL09 with periodic boundary conditions. The resulting solid is far denser than the laboratory sample (0.87 instead of 0.53 g/cm 3 ), showing that the model crosslinking is excessive.…”

“…In particular, the PAF material formed with biphenyl chains (called PAF-1 or PAF-302 in the literature, and synthesized from tetrabromophenylmethane through Yamamoto homo-coupling reaction) has also been exploited for gas adsorption, with excellent uptakes of methane [31][32][33] and CO 2 . [34][35][36] The hypercrosslinked aromatic polymer studied in this paper is obtained by Friedel-Crafts condensation of tetraphenylethene (TPM) and formaldehyde dimethyl acetal (FDA), 6,37 and is referred to as mPAF (i.e. microPorous Aromatic Framework, in analogy to the PAF family mentioned above).…”