Single-Crystal to Single-Crystal Mechanical Contraction of Metal–Organic Frameworks through Stereoselective Postsynthetic Bromination

Abstract

The properties of metal-organic frameworks (MOFs) can be tuned by postsynthetic modification (PSM) to introduce specific functionalities after their synthesis. Typically, PSM is carried out on pendant functional groups or through metal/ligand exchange, preserving the structure of the MOF. We report herein the bromination of integral alkyne units in a pair of Zr(4+) and Hf(4+) MOFs, which proceeds stereoselectively in a single-crystal to single-crystal manner. The chemical and mechanical changes in the MOFs are extensively characterized, including the crystal structures of the postsynthetically brominated materials, which show a mechanical contraction of up to 3.7% in volume. The combination of stability and chemical reactivity in these MOFs leads to the possibility of tuning mechanical properties by chemical transformation while also opening up new routes to internal pore functionalization.

Stereoselective Halogenation of Integral Unsaturated C‐C Bonds in Chemically and Mechanically Robust Zr and Hf MOFs

“…The PXRD pattern of the brominated material, 4‐Br 4 , reveals that crystallinity is retained during the transformation (Figure 3 b) and it is clear that peak positions have moved to slightly higher values of 2 θ upon bromination, indicative of the conversion of alkyne to dibromoalkene units and the mechanical contraction that results 23a…”

“…Additionally, crystals of iodinated linkers separated from a number of the [D 6 ]DMSO/D 2 SO 4 digest solutions (see Supporting Information, Section S11), allowing us to crystallographically characterise trans ‐edb‐I 2 ‐H 2 ,23a trans , trans ‐bdb‐I 4 ‐H 2 and trans , trans ‐peb‐I 4 ‐H 2 , from the iodination of 2 , 3 and 4 , in turn (Figure 5 b‐5d). These results unambiguously show that the chemical stability of Zr MOFs, in concert with reactive chemisorptive sites on the linkers, generates potential candidates for I 2 storage/capture applications.…”

Postsynthetic Modification of Metal‐Organic Frameworks through Click Chemistry

“…Postsynthetic modification (PSM), [30][31][32][33][34] as an alternative and simple method, has been widely used to functionalize MOFs in recent years. [36][37][38][39][40][41] Click chemistry, [42][43][44] which can proceed the reaction efficiently with high yields and high specificity in the presence of various functional groups, has received a great deal of use in different fields, for example, dendrimer synthesis [45,46] and surface science. Therefore, isoreticular MOFs with the same network topology can be prepared, and the resulting MOFs may show enhanced properties for specialized applications.…”

A Computational and Experimental Approach Linking Disorder, High‐Pressure Behavior, and Mechanical Properties in UiO Frameworks

“…We have found the amino acid l ‐proline to be a highly efficient modulator in the synthesis of Zr UiO‐MOFs 12. Addition of 5 and 1 equivalents (with respect to the linker) of l ‐proline and HCl (a known synthetic promoter13) during solvothermal syntheses yielded single crystals of ≈50 μm diameter of both UiO‐67 and UiO‐abdc (Supporting Information, Section SI‐1).…”