Understanding Gas Storage in Cuboctahedral Porous Coordination Cages

Published

July 4, 2019

Author(s)

Gregory R. Lorzing, Eric J. Gosselin, Benjamin Trump, Arthur H. P. York, Arni Sturluson, Casey A. Rowland, Glenn P. A. Yap, Craig Brown, Cory M. Simon, Eric D. Bloch

Abstract

Porous molecular solids are promising molecular solids are promising materials for gas storage applications. However, given the relative dearth of studies concerning these materials in this regard, additional adsorption and structural studies are vital for further understanding their properties and developing design parameters for materials optimization. Here we examine a series of isostructural cuboctahedral, paddlewheel-based coordination cages, M₂₄(Ut^Bu-bdc)₂₄ (M = Cr, Mo, Ru; ^tBu-bdc^2- = 5-tert-butylisophthalic acid), for high-pressure methane storage. As the decrease in crystallinity upon activation of these porous molecular materials precludes the use of diffraction studies, we turn to a related class of pillared coordination cage-based metal-organic frameworks, M₂₄(Me-bdc)₂₄(dabco)₆ (M= Fe, Co; Me-bdc^2- = 5-methylisophthalic acid; dabco = 1,4-diazabicyclo[2.2.2.]octane) for neutron diffraction studies. The five porous materials display BET surface areas from 1,060 - 1,938 m²/g and total methane uptake capacitiesof up to a 167 cm³/cm³. Both the porous cages and cage-based frameworks display methane adsorption enthalpies of -15 to -22 kJ/mol. Neutron diffraction studies indicate that the triangular windows of the cage are optimal methane adsorption sites with CD₄-arene interactions between 3.7 and 4.1 angstrom}. At both low and high loadings three additional methane adsorption sites are apparent. These results show that M6d24^L₂₄ cages are competent gas storage materials and further adsorption sites may be optimized by judicious ligand functionalization.

Citation

Journal of the American Chemical Society

Volume

141

Issue

30

Pub Type

Journals

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Keywords

metal organic frameworks, gas adsorption

Citation

Lorzing, G. , Gosselin, E. , Trump, B. , York, A. , Sturluson, A. , Rowland, C. , Yap, G. , Brown, C. , Simon, C. and Bloch, E. (2019), Understanding Gas Storage in Cuboctahedral Porous Coordination Cages, Journal of the American Chemical Society, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=927409 (Accessed April 18, 2024)