UTSA-74: A MOF-74 Isomer with Two Accessible Binding Sites per Metal Center for Highly Selective Gas Separation

Published

May 4, 2016

Author(s)

Feng Luo, Changsheng Yan, Lilong Dang, Rajamani Krishna, Wei Zhou, Hui Wu, Xinglong Dong, Yu Han, Tong-Liang Hu, Michael O'Keeffe, Lingling Wang, Mingbiao Luo, Rui-Biao Lin, Banglin Chen

Abstract

A new metal-organic framework Zn₂(H₂O)(dobdc)¿0.5(H₂O) (UTSA-74, H₄dobdc=2,5-dioxido-1,4- benzenedicarboxylic acid), Zn-MOF-74/CPO-27-Zn isomer, has been synthesized and structurally characterized. It has a novel four coordinated fgl topology with one-dimensional channels of about 8.0 Å. Unlike metal sites in the well-established MOF- 74 with a rod-packing structure in which each of them is in a five coordinate square pyramidal coordination geometry, there are two different Zn²⁺ sites within the binuclear secondary building units in UTSA-74 in which one of them (Zn1) is in a tetrahedral while another (Zn2) in an octahedral coordination geometry. After activation, the two axial water molecules on Zn2 sites can be removed, generating UTSA-74a with two accessible gas binding sites per Zn2 ion. Accordingly, UTSA-74a takes up moderately high and comparable amount of acetylene (145 cm³/cm³) to Zn-MOF-74. Interestingly, the accessible Zn²⁺ sites in UTSA-74a are bridged by carbon dioxide molecules instead of being terminally bound in Zn-MOF-74, so UTSA-74a adsorbs much smaller amount of carbon dioxide (90cm³/cm³) than Zn-MOF-74 (146 cm³/cm³) at room temperature and 1 bar, leading to a superior MOF material for highly selective C₂H₂/CO₂ separation. X-ray crystal structures, gas sorption isotherms, molecular modeling, simulated and experimental breakthrough comprehensively support this result.

Citation

Journal of American Chemical Society

Volume

138

Issue

17

Pub Type

Journals

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Keywords

Porous materials, Gas separation, Open metal sites

Citation

Luo, F. , Yan, C. , Dang, L. , Krishna, R. , Zhou, W. , Wu, H. , Dong, X. , Han, Y. , Hu, T. , O'Keeffe, M. , Wang, L. , Luo, M. , Lin, R. and Chen, B. (2016), UTSA-74: A MOF-74 Isomer with Two Accessible Binding Sites per Metal Center for Highly Selective Gas Separation, Journal of American Chemical Society, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=920850 (Accessed April 24, 2024)