Postsynthetic ligand exchange as a route to functionalization of ‘inert’ metal–organic frameworks

Abstract

Herein, we report that the exchange of ligands from an intact metal-organic framework (MOF) can be exploited as a means to introduce functionalized ligands into MOFs under mild conditions. It is shown that ligand exchange can occur with 'inert' Zr(IV)-based UiO-66 MOFs in a solvent dependent manner. We call this process postsynthetic exchange (PSE) and show that it provides access to MOFs that are not readily prepared in high quality by solvothermal methods. It was found that ligand exchange can occur between UiO-66 MOFs as monitored by aerosol time-of-flight mass spectrometry (ATOFMS). ATOFMS was used to analyze the chemical composition of microcrystalline MOFs on the single particle level, providing information not available through bulk analysis. PSE is an important postsynthetic approach to the modification of MOFs, and the ligand exchange revealed by ATOFMS requires a re-evaluation of the assumed 'stability' of even the most robust MOFs.

Fe3O4@HKUST-1 and Pd/Fe3O4@HKUST-1 as magnetically recyclable catalysts prepared via conversion from a Cu-based ceramic

“…[4][5][6][7] In addition, new synergetic properties have been obtained by incorporating functional species into MOFs, further expanding their potential applications. [8][9][10][11][12][13][14][15][16][17] While there are a large number of reports describing different methods for successfully combining exogenous species into MOFs, [18][19][20][21] the encapsulation of nanoparticles is particularly promising due to the innovative functional properties that cannot be obtained from the parent MOFs alone. [22][23][24][25][26] Typically, the encapsulation of nanoparticles is achieved through the introduction of precursors using solution impregnation, gas-phase infiltration or a solid-phase method, and subsequent conversion into the corresponding functional components inside the frameworks.…”

Lattice-imposed geometry in metal–organic frameworks: lacunary Zn4O clusters in MOF-5 serve as tripodal chelating ligands for Ni2+

“…Thus, Figure 3 shows a straightforward six-(O h ) to five-(C 4v ) to four-(pseudo-T d ) coordinate conversion of Ni in a +2 formal oxidation state. These transformations, illustrated in Scheme 1, are 50 supported by computational modeling of (DMF) y NiZn 3 O(benzoate) 6 (y = 0, 1, 2) clusters containing six-, five-, and four-coordinate Ni 2+ ions with two, one, or no bound DMF molecules. As shown in Figure S7, time-dependent DFT calculations using optimized geometries of these clusters 55 predicted electronic absorption spectra that agreed well with the assigned yellow, red, and blue traces in Figure 3.…”

“…This is confirmed by a nearly (0,0) . Therefore, NiZn 3 O(carboxylate) 6 clusters can only be stabilized in the MOF lattice.…”

Preparation of Hydrophobic Metal-Organic Frameworks via Plasma Enhanced Chemical Vapor Deposition of Perfluoroalkanes for the Removal of Ammonia

“…. The degree of fluorination and confirmation of CF x species type can be done with 20 F magic angle spinning (MAS) nuclear magnetic resonance (NMR), as can be seen in Figure 3, or x-ray photoelectron spectroscopy (XPS). The two main fluorine species observed in this sample are CF 2 groups at δ ~ -87 ppm and CF at δ ~ -152 ppm 18 .…”