TY - JOUR
T1 - Understanding methane adsorption in porous aromatic frameworks
T2 - An FTIR, Raman, and theoretical combined study
AU - Errahali, M.
AU - Gatti, G.
AU - Tei, L.
AU - Canti, L.
AU - Fraccarollo, A.
AU - Cossi, M.
AU - Marchese, L.
PY - 2014/5/15
Y1 - 2014/5/15
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=84900797230&partnerID=8YFLogxK
U2 - 10.1021/jp412572e
DO - 10.1021/jp412572e
M3 - Article
SN - 1932-7447
VL - 118
SP - 10053
EP - 10060
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 19
ER -