Understanding methane adsorption in porous aromatic frameworks: An FTIR, Raman, and theoretical combined study

M. Errahali, G. Gatti, L. Tei, L. Canti, A. Fraccarollo, M. Cossi, L. Marchese

Risultato della ricerca: Contributo su rivistaArticolo in rivistapeer review

Abstract

We present a vibrational study of PAF-302, belonging to the class of porous aromatic frameworks (PAFs), recently synthesized and applied in several applications involving gas adsorption. The precursor, tetrakis(4-bromophenyl) methane (TBPM), and the polymer were studied with FTIR and Raman spectroscopies to investigate the structure of PAF-302, whereas the system after methane adsorption was studied by FTIR, also varying the CH4 loading, to get some hints on the strength of the interactions with adsorbed methane. Theoretical calculations of the harmonic frequencies of TBPM, methane, and methane/aromatic model systems were performed at high theory level (MP2 with extended basis set) to support the assignment of vibrational bands and to estimate the interactions causing the observed frequency shifts upon methane adsorption. The analysis shows that the polymerization process is essentially complete and that the adsorbed CH4 molecules interact with two phenyl rings, though stronger interactions can be envisaged. The computed interaction energies are compatible with the isosteric heats of adsorption previously measured for methane in PAF-302. A Grand Canonical Monte Carlo (GCMC) approach was used to simulate CH4 adsorption isotherms at different temperatures (87-115 K) and in the 0-0.020 bar pressure range, thus allowing us to estimate the loading of methane in the FTIR adsorption study.

Lingua originaleInglese
pagine (da-a)10053-10060
Numero di pagine8
RivistaJournal of Physical Chemistry C
Volume118
Numero di pubblicazione19
DOI
Stato di pubblicazionePubblicato - 15 mag 2014

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