Guest-Dependent Single-Crystal-to-Single-Crystal Phase Transitions in a Two-Dimensional Uranyl-Based Metal-Organic Framework

Two-dimensional metal-organic frameworks (2D-MOFs) have shown promise in gas storage and separation applications due to their structural isomerism in response to external stimuli such as temperature, mechanical pressure, and/or guest molecules. Here, we report the guest-dependent phase transitions of a uranyl-based 2D-MOF, NU-1302, observed as single-crystal-to-single-crystal transformations. Different stacking configurations of the same structure were observed in DMF and ethanol, and after supercritical CO ₂ activation. The structural isomerism upon exposure to different solvents and when solvent-free demonstrated the ability of this system to respond to guests by shifting neighboring 2D sheets, resulting in the expansion or contraction of one-dimensional channels.