Adsorption Properties of MFM-400 and MFM-401 with CO2 and Hydrocarbons: Selectivity Derived from Directed Supramolecular Interactions

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• 作者：Ilich A. Ibarra ; Amber Mace ; Sihai Yang ; Junliang Sun ; Sukyung Lee ; Jong-San Chang ; Aatto Laaksonen ; Martin Schröder ; Xiaodong Zou
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：August 1, 2016
• 年：2016
• 卷：55
• 期：15
• 页码：7219-7228
• 全文大小：676K
• 年卷期：0
• ISSN：1520-510X

文摘

([Sc₂(OH)₂(BPTC)]) (H₄BPTC = biphenyl-3,3′,5,5′-tetracarboxylic acid), MFM-400 (MFM = Manchester Framework Material, previously designated NOTT), and ([Sc(OH)(TDA)]) (H₂TDA = thiophene-2,5-dicarboxylic acid), MFM-401, both show selective and reversible capture of CO₂. In particular, MFM-400 exhibits a reasonably high CO₂ uptake at low pressures and competitive CO₂/N₂ selectivity coupled to a moderate isosteric heat of adsorption (Q_st) for CO₂ (29.5 kJ mol^–1) at zero coverage, thus affording a facile uptake–release process. Grand canonical Monte Carlo (GCMC) and density functional theory (DFT) computational analyses of CO₂ uptake in both materials confirmed preferential adsorption sites consistent with the higher CO₂ uptake observed experimentally for MFM-400 over MFM-401 at low pressures. For MFM-400, the Sc–OH group participates in moderate interactions with CO₂ (Q_st = 33.5 kJ mol^–1), and these are complemented by weak hydrogen-bonding interactions (O···H–C = 3.10–3.22 Å) from four surrounding aromatic −CH groups. In the case of MFM-401, adsorption is provided by cooperative interactions of CO₂ with the Sc–OH group and one C–H group. The binding energies obtained by DFT analysis for the adsorption sites for both materials correlate well with the observed moderate isosteric heats of adsorption for CO₂. GCMC simulations for both materials confirmed higher uptake of EtOH compared with nonpolar vapors of toluene and cyclohexane. This is in good correlation with the experimental data, and DFT analysis confirmed the formation of a strong hydrogen bond between EtOH and the hydrogen atom of the hydroxyl group of the MFM-400 and MFM-401 framework (FW) with H–O_EtOH···H–O_FW distances of 1.77 and 1.75 Å, respectively. In addition, the accessible regeneration of MFM-400 and MFM-401 and release of CO₂ potentially provide minimal economic and environmental penalties.