4.7 Article

Size exclusion propyne/propylene separation in an ultramicroporous yet hydrophobic metal-organic framework

Journal

INORGANIC CHEMISTRY FRONTIERS
Volume 9, Issue 19, Pages 4952-4961

Publisher

ROYAL SOC CHEMISTRY
DOI: 10.1039/d2qi01152b

Keywords

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Funding

  1. National Natural Science Foundation of China [22038001, 51621003]

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In this study, two ultramicroporous Zn-MOFs were introduced for propyne/propylene separation. The results showed that one of the MOFs exhibited high hydrophobicity and hydrolytic stability, and could adsorb propyne while excluding propylene.
Propyne/propylene separation is important in the petrochemical industry but challenging due to their similar physical properties and close molecular sizes. Herein, we present two isoreticular ultramicroporous Zn(II)-MOFs, Zn-2(ATZ)(2)(TPDC) (BUT-305, H2TPDC = [1,1 ':3 ',1 ''-terphenyl]-4,4 ''-dicarboxylic acid, HATZ = 3-amino-1,2,4-triazole) and Zn-2(ATZ)(2)(MeTPDC) (BUT-306, H2MeTPDC = 5 '-methyl-[1,1 ':3 ',1 ''-terphenyl]-4,4 ''-dicarboxylic acid). The pore aperture of BUT-306 (similar to 1.6 angstrom) is smaller than that of BUT-305 due to the presence of extra gate-like methyl groups in the 1D channels of the former. With a narrow and hydrophobic pore aperture, BUT-306 exhibits high hydrophobicity and hydrolytic stability and adsorbs C3H4 but excludes C3H6 in a wide temperature range. The C3H6 and C3H4 adsorption capacities of BUT-306 at 298 K and similar to 1 bar were 2.4 and 29.6 cm(3) g(-1), respectively. Dynamic column breakthrough experiments confirmed the high capability of BUT-306 to remove C3H4 from the equimolar binary gas mixture of C3H4 and C3H6. The C3H4/C3H6 separation performance of BUT-306 was largely retained even when the binary C3H4/C3H6 gas for breakthrough experiments was pre-saturated with water vapor. In addition, the single-crystal structure of C3H4-loaded BUT-306 was determined, which revealed that the adsorbed C3H4 molecules were located in the center of channel cavities and interacted with the MOF by multiple weak C delta-MIDLINE HORIZONTAL ELLIPSISC delta+ dipole-dipole interactions and C-HMIDLINE HORIZONTAL ELLIPSIS interactions. This work demonstrates the high potential of an ultramicroporous, hydrophobic, and hydrolytically stable MOF in the removal of C3H4 from the C3H4/C3H6 gas mixture by size exclusion adsorption. The structure and gas adsorption studies shed light on the design and synthesis of new adsorbents for the separation of light hydrocarbons.

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