A Flexible Metal–Organic Framework with 4-Connected Zr₆ Nodes

Abstract

Zr-based metal-organic frameworks (MOFs) have been known for their excellent stability; however, due to the high connectivity of the Zr nodes, it is challenging to introduce flexibility into Zr-MOFs. Here we present a flexible Zr-MOF named NU-1400 comprising 4-connected Zr nodes and tetratopic linkers. It exhibits guest-dependent structural flexibility with up to 48% contraction in the unit cell volume as evidenced by single-crystal X-ray diffraction studies. The expanded or contracted conformations of NU-1400 showed drastically different reactivity toward the hydrolysis of a nerve agent simulant owing to the size-selective effect toward the reactant.

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A Flexible Interpenetrated Zirconium‐Based Metal–Organic Framework with High Affinity toward Ammonia

“…Whereas the majority of Zr‐MOFs are rigid owing to the high connectivity of the Zr 6 nodes, some are reported to be flexible by employing nonrigid linkers or by reducing the connectivity of Zr 6 nodes, resulting in structural changes upon exposure to external stimuli such as guest molecules, temperature, and pressure . In our previous work, a flexible MOF (NU‐1400) comprising 4‐connected Zr 6 nodes and tetratopic linkers, was synthesized, and the framework presents different conformations and tunable accessibility to the Lewis‐acidic Zr IV sites induced by the guest molecules . Because NU‐1400 exhibits an edge‐transitive lvt topology that could allow for interpenetration, it was postulated that elongating the tetratopic organic linker could give a catenated network, which can further increase the complexity of the flexibility modes and dynamics of the system, given the possibilities of both intra‐ and inter‐framework motions.…”

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