Hybrid Zeolitic Imidazolate Frameworks: Controlling Framework Porosity and Functionality by Mixed-Linker Synthesis

Abstract

Zeolitic imidazolate frameworks (ZIFs) are a subclass of nanoporous metal−organic frameworks (MOFs) that exhibit zeolite-like structural topologies and have interesting molecular recognition properties, such as molecular sieving and gate-opening effects associated with their pore apertures. The synthesis and characterization of hybrid ZIFs with mixed linkers in the framework are described in this work, producing materials with properties distinctly different from the parent frameworks (ZIF-8, ZIF-90, and ZIF-7). NMR spectroscopy is used to assess the relative amounts of the different linkers included in the frameworks, whereas nitrogen physisorption shows the evolution of the effective pore size distribution in materials resulting from the framework hybridization. X-ray diffraction shows these hybrid materials to be crystalline. In the case of ZIF-8-90 hybrids, the cubic space group of the parent frameworks is continuously maintained, whereas in the case of the ZIF-7-8 hybrids there is a transition from a cubic to a rhombohedral space group. Nitrogen physisorption data reveal that the hybrid materials exhibit substantial changes in gate-opening phenomena, either occurring at continuously tunable partial pressures of nitrogen (ZIF-8-90 hybrids) or loss of gate-opening effects to yield more rigid frameworks (ZIF-7-8 hybrids). With this synthetic approach, significant alterations in MOF properties may be realized to suit a desired separation or catalytic process.

The oxamate route, a versatile post-functionalization for metal incorporation in MIL-101(Cr): Catalytic applications of Cu, Pd, and Au

“…Stability issues were solved by combining late transition metals and functional benzene dicarboxylates (X-BDC; X = -NO 2 , -NH 2 , -Br, -OCH 3 , -CH 3 , -F, -Cl) [17][18][19]. The use of several functional organic sites within a single MOF crystal by approaches like mix-linker or post-synthetic exchange has also attracted a lot of interest during the last few years [12,[20][21][22][23][24][25]. More complex pre-functionalized linkers, like homochiral ligands for asymmetric catalysis and enantioselective separation [26,27], or metallo-ligands enabling immobilization of a wide variety of active open metal sites have also been explored by several research groups [28][29][30].…”

A high-flux polyimide hollow fiber membrane to minimize footprint and energy penalty for CO2 recovery from flue gas

“…While ZIF-8 has demonstrated thermal stability and stability to basic solutions [42], it is known that the ZIF is susceptible to even weak acids [43]. We hypothesize here that the pendant carboxylic acid on the solvated 6FDA-DAM:DABA(4:1) chains de-stabilize the exterior of the metalimidazole framework and these pendant moieties subsequently crosslink to the ZIF particles.…”

Carbon dioxide selective mixed matrix composite membrane containing ZIF-7 nano-fillers

“…Some reports claimed that no adsorption was found for nitrogen in ZIF-7 [37,38], but the type 1 nitrogen sorption isotherm in Fig. 1.…”