ABSTRACT
We describe the first meltable iron-based zeolitic imidazolate framework (ZIF), denoted MUV-24. This material, elusive from direct synthesis, is obtained from the thermal treatment of [Fe3(im)6(Him)2], which yields Fe(im)2 upon loss of the neutral imidazole molecules. Different crystalline phase transformations are observed upon further heating, until the material melts at 482 °C. Vitrification upon cooling of the liquid phase gives rise to the first Fe-metal-organic framework glass. X-ray total scattering experiments show that the tetrahedral environment of the crystalline solids is maintained in the glass, whereas nanoindentation measurements reveal an increase in Young's modulus, in agreement with stiffening upon vitrification.
ABSTRACT
Bond breaking has emerged as a new tool to postsynthetically modify the pore structure in metal-organic frameworks since it allows us to obtain pore environments in structures that are inaccessible by other techniques. Here, we extend the concept of clip-off chemistry to archetypical ZIF-8, taking advantage of the different stabilities of the bonds between imidazolate and Zn and Fe metal atoms in heterometallic Fe-Zn-ZIF-8. We demonstrate that Fe centers can be removed selectively without affecting the backbone of the structure that is supported by the Zn atoms. This allows us to create mesopores within the highly stable ZIF-8 structure. The strategy presented, combined with control of the amount of iron centers incorporated into the structure, permits porosity engineering of ZIF materials and opens a new avenue for designing novel hierarchical porous frameworks.
ABSTRACT
The isolation of high-quality flakes of 2D MOFs in large amounts remains a challenge. In this work, we obtained nanosheets for a whole family of Fe-based magnetic MOFs, MUV-1-X, through a liquid exfoliation procedure. High-quality crystalline layers with lateral sizes of 8 µm and thicknesses of 4 nm, which retain the structural integrity and magnetic properties, are obtained.