A Stimuli-Responsive Zirconium Metal-Organic Framework Based on Supermolecular Design

A flexible, yet very stable metal-organic framework (DUT-98, Zr6O4(OH)(4)(CPCDC)(4)(H2O)(4), CPCDC = 9-(4-carboxyphenyl)-9H-carbazole-3,6-dicarboxylate) was synthesized using a rational supermolecular building block approach based on molecular modelling of metal-organic chains and subsequent virtual interlinking into a 3D MOF. Structural characterization via synchrotron single-crystal X-ray diffraction (SCXRD) revealed the one-dimensional pore architecture of DUT-98, envisioned in silico. After supercritical solvent extraction, distinctive responses towards various gases stimulated reversible structural transformations, as detected using coupled synchrotron diffraction and physisorption techniques. DUT-98 shows a surprisingly low water uptake but a high selectivity for pore opening towards specific gases and vapors (N-2, CO2, n-butane, alcohols) at characteristic pressure resulting in multiple steps in the adsorption isotherm and hysteretic behavior upon desorption.