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RESEARCH PRODUCT

Efficient Gas Separation and Transport Mechanism in Rare Hemilabile Metal–Organic Framework

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Understanding/visualizing the established interactions between gases and adsorbents is mandatory to implement better performance materials in adsorption/separation processes. Here we report the unique behavior of a rare example of a hemilabile chiral three-dimensional metal–organic framework (MOF) with an unprecedented qtz-e-type topology, with formula CuII2(S,S)-hismox·5H2O (1) (hismox = bis[(S)-histidine]oxalyl diamide). 1 exhibits a continuous and reversible breathing behavior, based on the hemilability of carboxylate groups from l-histidine. In situ powder (PXRD) and single crystal X-ray diffraction (SCXRD) using synchrotron radiation allowed us to unveil the crystal structures of four different host–guest adsorbates (Ar@1, N2@1, CO2@1, and C3H6@1), rationalize the breathing motion, and unravel the mechanisms governing the adsorption of these gases. Then this information was transferred to implement efficient separations of mixtures of industrial and environmental relevance, CO2/N2, CO2/CH4, and C3H8/C3H6, using 1 in packed columns as the stationary phase and dispersed in a mixed matrix membrane. This work was supported by the MINECO (Spain) (projects CTQ2016-75671-P, MAT2017-86992-R, and MAT-80285-P and Excellence Unit “Maria de Maeztu” MDM-2015-0538) and the Ministero dell’Istruzione, dell’Università e della Ricerca (Italy). M.M. and E.T. thank the MINECO, and R.B. thanks the MIUR (project PON R&I FSE-FESR 2014-2020) for predoctoral grants. Thanks are also extended to the “Programa post-Ramón y Cajal de la Universidad de Valencia (E.P.)”, the “Fondo per il finanziamento delle attivita base di ricerca” (D.A.), and the “Atracció de talent-contractes postdoctorals de la Universitat de Valencia” and “Juan de la Cierva-Incorporación-2017” programs (J.F.-S.). E.P. acknowledges the financial support of the European Research Council under the European Union’s Horizon 2020 research and innovation programme/ERC grant agreement no. 814804, MOF-reactors.