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oai:figshare.com:article/34040604 2026-10-01T07:07:48Z category_1 category_146 category_21 category_272 category_873 category_734 category_106 portal_63 item_type_6 month_year_10_2026

Flexible Nickel-Fumarate Metal–Organic Framework Exhibiting Reversible Single-Crystal-to-Single-Crystal Phase Transformation for Adsorptive Separation of Water–Organic Azeotropic Mixtures Yi Cheng (317041) Bochun Zhang (25153755) Qingqing Yan (752158) Yafei Du (6751067) Shuyi An (783243) Xiaohe Miao (1333908) Sujing Wang (2297509) Biophysics Space Science Biotechnology Environmental Sciences not elsewhere classified Chemical Sciences not elsewhere classified Biological Sciences not elsewhere classified Science Policy triggering relative displacement rt ); ethanol low relative pressures layered inorganic blocks induced structural adaptability efficient azeotropic dehydration delivering excellent h broad pressure range alternative structural paradigm flexible mof built constricting pores along organic selectivity across first reversible 1d – ni linkages reversible ni – 2 </ sub 2d sbu single crystal phase transformation ni – preengineered pores flexible nickel temperature phase reversible single work reports thermal activation tested organics similar molecules show promise original room nickel ions negligible uptake major challenge limiting discrimination fumaric acid designing stimuli bond reorganization based separation adsorptive separation adjacent one 393 k Separating water–organic solvent azeotropes remains a major challenge, rendering conventional distillation ineffective. While metal–organic frameworks (MOFs) show promise for adsorption-based separation, most rely on static, preengineered pores, limiting discrimination between similar molecules. Here, we report Ni-fum, a flexible MOF built from nickel ions and fumaric acid, that undergoes a reversible single-crystal-to-single-crystal transition and achieves highly selective water adsorption from azeotropic organic solvents via guest-induced structural adaptability. Thermal activation at 393 K under vacuum removes guest molecules and coordinated water, triggering relative displacement of adjacent one-dimensional (1D) Ni–O chains and forming interchain Ni–O–Ni linkages. This reorganizes 1D secondary building units (SBUs) into two-dimensional (2D) layered inorganic blocks, constricting pores along the <i>a</i> axis to yield the high-temperature phase, Ni-fum-HT. Crucially, this transformation is water-specific: only water fully restores Ni-fum-HT to its original room-temperature phase (Ni-fum-RT); ethanol, isopropanol, THF, and acetonitrile do not. Leveraging this selectivity, Ni-fum-HT exhibits high water uptake at low relative pressures but a negligible uptake of the tested organics, delivering excellent H₂O/organic selectivity across a broad pressure range. This work reports the first reversible 1D-to-2D SBU single-crystal-to-single-crystal transformation, in which reversible Ni–O bond reorganization and water-triggered structural recovery underpin selective adsorption, providing an alternative structural paradigm for designing stimuli-responsive MOFs toward energy-efficient azeotropic dehydration. 2026-10-01T00:00:00Z Text Journal contribution 10.1021/prechem.6c00111.s001 https://figshare.com/articles/journal_contribution/Flexible_Nickel-Fumarate_Metal_Organic_Framework_Exhibiting_Reversible_Single-Crystal-to-Single-Crystal_Phase_Transformation_for_Adsorptive_Separation_of_Water_Organic_Azeotropic_Mixtures/34040604 CC BY-NC 4.0