Metastable Zr/Hf-MOFs: the hexagonal family of EHU-30 and their water-sorption induced structural transformation

Maite Perfecto-Irigaray; Garikoitz Beobide; Sofia Calero; Oscar Castillo; Ivan da Silva; J. José Gutierrez Sevillano; Antonio Luque; Sonia Pérez-Yáñez; Leticia F. Velasco

doi:10.1039/D1QI00997D

Metastable Zr/Hf-MOFs: the hexagonal family of EHU-30 and their water-sorption induced structural transformation†

Maite Perfecto-Irigaray,

^a Garikoitz Beobide,

*^ab Sofia Calero,

^cd Oscar Castillo,

*^ab Ivan da Silva,

^e J. José Gutierrez Sevillano,

^d Antonio Luque,^ab Sonia Pérez-Yáñez

^abf and Leticia F. Velasco^g

Author affiliations

* Corresponding authors

^a Departamento de Química Orgánica e Inorgánica, Facultad de Ciencia y Tecnología, Universidad del País Vasco/Euskal Herriko Unibertsitatea, UPV/EHU, Apartado 644, E-48080 Bilbao, Spain
E-mail: garikoitz.beobide@ehu.eus, oscar.castillo@ehu.eus

^b BCMaterials, Basque Center for Materials, Applications and Nanostructures, UPV/EHU Science Park, 48940 Leioa, Spain

^c Materials Simulation & Modeling, Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands

^d Department of Physical, Chemical and Natural Systems, Universidad Pablo de Olavide, Ctra. Utrera Km. 1, 41013 Seville, Spain

^e ISIS Facility, STFC Rutherford Appleton Laboratory, Chilton, Oxfordshire OX11 0QX, UK

^f Departamento de Química Orgánica e Inorgánica, Facultad de Farmacia, Universidad del País Vasco/Euskal Herriko Unibertsitatea, UPV/EHU, E-01006 Vitoria-Gasteiz, Spain

^g Department of Chemistry, Royal Military Academy, Renaissancelaan 30, 1000 Brussels, Belgium

Abstract

UiO-66, reported in 2008, inspired the ongoing chemistry of group 4 metal–organic frameworks and it is still one of the most studied MOFs due to its exceptional stability. The tightness of their building blocks and bond strength make it tough to access new topologies, unless the building blocks are changed or defect engineering is employed, which in turn lead to different nominal stoichiometries. However, well selected structure directing agents and harsh synthesis conditions allowed the isolation of the first polymorph of UiO-66, named EHU-30. Herein, we provide evidence for the generalization of the synthetic approach with four new EHU-30 isoreticular compounds, based on amino-functionalized linkers and zirconium and hafnium as metal centres: EHU-30-NH₂(M) and EHU-30-NHR(M) (M: Zr, Hf; R: 2-carboxypropyl). The crystal structure analysis reveals that their framework is more porous than that of their polymorphic counterpart. Furthermore, due to the current relevance of MOFs in greenhouse gas capture and in water harvesting methodologies, we have explored CO₂ and water vapour adsorption on the new polymorphic phases, by means of experimental and computational resources, and compared to the parent EHU-30. The amino functionalization makes the EHU-30 series more prone to CO₂ and water vapour adsorption. Besides, the water adsorption isotherms show an interesting crossing sensitive to temperature, sorption cycles and functionalization of the linker, which has been attributed to a localized structural transformation from EHU-30 to UiO-66. Finally, time-of-flight (TOF) powder neutron diffraction experiments were also conducted to locate the preferred adsorption sites for water in functionalized and parent EHU-30 structures.

Inorganic Chemistry Frontiers

Metastable Zr/Hf-MOFs: the hexagonal family of EHU-30 and their water-sorption induced structural transformation†

Abstract

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Metastable Zr/Hf-MOFs: the hexagonal family of EHU-30 and their water-sorption induced structural transformation

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