Revealing Disorder, Sorption Locations and a Sorption-Induced\nSingle Crystal–Single Crystal Transformation in a Rare-Earth <i>fcu</i>-Type Metal–Organic Framework

Rare-earth metal–organic\nframeworks (RE-MOFs) formed in\nthe presence of fluoride donors are a group of complex and applicable\nMOFs. Determining structural complexity is crucial in applying such\nMOFs and has been achieved to uncover framework disorders in the important <i>fcu</i> framework topology MOF, Y-ndc-<i>fcu</i>-MOF\n(<b>1</b>). <b>1</b> is found to contain F<sup>–</sup> groups disordered over the μ<sub>3</sub>-face-capping sites\nin its secondary building unit (SBU) and framework distortions upon\nsorption of different guest molecules. The favored location of the\nguests is within the octahedral cage of <b>1</b> where they\ninteract with the Y<sup>3+</sup> centers. The size, shape, and interactions\nof the different guests lead to subtle distortions within the SBU\nand adoption of specific orientations of the naphthalene group of\nthe 1,4-naphthalenedicarboxylate framework linkers. The sorption of\nDMF<sub>(l)</sub>/H<sub>2</sub>O<sub>(l)</sub> lowers the symmetry\nfrom cubic <i>Fm</i>3̅<i>m</i> (for MeOH<sub>(l)</sub>, N<sub>2(g)</sub>, CO<sub>2(g or l)</sub>) to\ncubic <i>Pa</i>3̅ (for DMF<sub>(l)</sub>/H<sub>2</sub>O<sub>(l)</sub>) symmetry with retention of the <i>fcu</i> topology, and conversion between the <i>Pa</i>3̅\nand <i>Fm</i>3̅<i>m</i> structures is induced\nby solvent exchange. Such disorder and sorption locations and transformation\nare important considerations during the optimization and application\nof MOFs for sorption-based technologies.