Flexible metal-organic frameworks (MOFs) receive much attention owing to their attractive properties that originate from their flexibility and dynamic behavior, and show great potential applications in many fields. Here, recent progress in the discovery, understanding, and property investigations of flexible MOFs are reviewed, and the examples of their potential applications in storage and separation, sensing, and guest capture and release are presented to highlight the developing trends in flexible MOFs.

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Metal-organic frameworks (MOFs) constructed with metal ions/clusters and organic ligands have emerged as an important family of porous materials for various applications. However, the stability of this class of materials is crucial for their practical applications, which might be improved by varying their chemical composition and/or structurally tuning them. To fabricate MOFs with high stability, several strategies for enhancing the stability of MOFs have been developed, in which the strength of metal-ligand bonds is especially considered: the use of highly charged cations and higher pKa ligands, and varying the chemical functionality of linkers. On the other hand, the regulation of their structural architectures is also investigated: interpenetrated frameworks, multi-walled frameworks, and self-strengthening of the frameworks. In addition, the surface modification can also improve the stability of the materials. In this review, we introduce and summarize these strategies from the viewpoint of structural tuning and component choosing, providing useful instructions for the further design and synthesis of MOFs with high-level stability.

We herein report an ew coordination network that deforms in as mooth and reversible manner under either thermal or pressure stimulation. Concomitantly,t he organic fluorophores coordinatively bound to the channel in aface-toface arrangement respond to this structural deformation by finely adapting their conformation and arrangement. As ar esult, the material exhibits ar emarkable dual-stimuliresponsive luminescence shift across almost the entire visible region:T he emission color of the crystal gradually changes from cyan to green upon heating and then to red upon pressure compression. Furthermore,each stage exhibits alinear dependence of both the emission maximum and intensity on the stimulus and is fully reversible.

The preparation of a highly water stable and porous lanthanide metal-organic framework (MOF) nanoparticles (denoted SUMOF-7II; SU refers to Stockholm University) is described. SUMOF-7II was synthesized starting from the tritopic linker of 2,4,6-trip -carboxyphenyl pyridine (H 3 L2) and La(III) as metal clusters. SUMOF-7II forms a stable dispersion and displays high fluorescence emission with small variation over the pH range of 6 to 12. Its fluorescence is selectively quenched by Fe(III) ions compared to other metal ions. The intensity of the fluorescene emission drops drops linearly in 16.6-167 μM Fe(III) concentration range, and Stern-Volmer plots are linear. The limit of detection (LOD) is 16.6 μM (at an S/N ratio of >3). This indicator probe can also be used for selective detection of tryptophan among several amino acids. Compared to the free linker H 3 L2, SUMOF-7II offers improved sensitivity and selectivity of the investigated species.

Multiple switchable physical properties have been demonstrated in one single niccolite structural metal-organic framework, [(CH CH ) NH ][Fe Fe (HCOO) ] (1), including (i) a reversible ferroelastic phase transition triggered by freezing the disordered (CH CH ) NH cations, (ii) a thermally switchable dielectric constant transition accompanied by phase transition, and (iii) thermal and positive magnetic field driven magnetic poles reversal at low temperatures, attributed to different responses of the magnetization of Fe and Fe sublattices to external stimuli. More interestingly, the exchange anisotropy between the two sublattices can also give rise to tunable positive and negative exchange bias fields. Straightforwardly, such diverse demonstrations of bistability in one single material (depending on the specific tuning way) will provide extra freedom and flexibility for the design of switcher devices.

Although great achievements have been made in the synthesis of giant lanthanide clusters, novel structural models are still scarce. Herein, we report a giant lanthanide cluster Dy76, constructed from [Dy3(μ3‐OH)4] and [Dy5(μ4‐O)(μ3‐OH)8] building blocks. As the largest known Dy cluster, the structure of Dy76 can be seen as arising from the fusion of two Dy48 clusters; these clusters can be isolated under various synthetic conditions and were characterized by single‐crystal X‐ray diffraction. This new, fused structural model of the pillar motif has not been found in Ln clusters. Furthermore, the successful conversion of Dy76 back into Dy48 in a retrosynthetic manner supports the proposed fusion formation mechanism of Dy76. Electrospray ionization mass spectrometry (ESI‐MS) analysis suggests that the metal cluster skeleton of Dy76 shows good stability in various solvents. This work not only reveals a new structural type of Ln clusters but also provides insight into the novel fusion assembly process.