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

Rare-earth metal-organic frameworks (RE-MOFs) formed in the presence of fluoride donors are a group of complex and applicable MOFs. Determining structural complexity is crucial in applying such MOFs and has been achieved to uncover framework disorders in the important <i>fcu</i> framework topology MOF, Y-ndc-<i>fcu</i>-MOF (<b>1</b>). <b>1</b> is found to contain F^- groups disordered over the μ₃-face-capping sites in its secondary building unit (SBU) and framework distortions upon sorption of different guest molecules. The favored location of the guests is within the octahedral cage of <b>1</b> where they interact with the Y³⁺ centers. The size, shape, and interactions of the different guests lead to subtle distortions within the SBU and adoption of specific orientations of the naphthalene group of the 1,4-naphthalenedicarboxylate framework linkers. The sorption of DMF_(l)/H₂O_(l) lowers the symmetry from cubic <i>Fm</i>3̅<i>m</i> (for MeOH_(l), N_2(g), CO_{2(g or l)}) to cubic <i>Pa</i>3̅ (for DMF_(l)/H₂O_(l)) symmetry with retention of the <i>fcu</i> topology, and conversion between the <i>Pa</i>3̅ and <i>Fm</i>3̅<i>m</i> structures is induced by solvent exchange. Such disorder and sorption locations and transformation are important considerations during the optimization and application of MOFs for sorption-based technologies.