Acoustomicrofluidic Defect Engineering and Ligand Exchange in ZIF‐8 Metal–Organic Frameworks

Abstract

A way through which the properties of metal-organic frameworks (MOFs) can be tuned is by engineering defects into the crystal structure. Given its intrinsic stability and rigidity, however, it is difficult to introduce defects into zeolitic imidazolate frameworks (ZIFs)-and ZIF-8, in particular-without compromising crystal integrity. In this work, it is shown that the acoustic radiation pressure as well as the hydrodynamic stresses arising from the oscillatory flow generated by coupling high frequency (MHz-order) hybrid surface and bulk acoustic waves into a suspension of ZIF-8 crystals in a liquid pressure transmitting medium is capable of driving permanent structural changes in their crystal lattice structure. Over time, the enhancement in the diffusive transport of guest molecules into the material's pores as a consequence is shown to lead to expansion of the pore framework, and subsequently, the creation of dangling-linker and missing-linker defects, therefore offering the possibility of tuning the type and extent of defects engineered into the MOF through the acoustic exposure time. Additionally, the practical utility of the technology is demonstrated for one-pot, simultaneous solvent-assisted ligand exchange under ambient conditions, for sub-micron-dimension ZIF-8 crystals and relatively large ligands-more specifically 2-aminobenzimidazole-without compromising the framework porosity or overall crystal structure.

Enhanced Iodine Capture Using a Postsynthetically Modified Thione–Silver Zeolitic Imidazole Framework

“…However, defects can also have a substantial impact on the properties and performances of porous materials, and investigations are beginning to give experimental/computational attention to the occurrence of structural defects in bulk porous solids, , including ZIF-8 specifically . A recent report even invokes SALE as a method to fill defective ZIF-8 sites with new ligands . Intuitively, it is feasible that the reintroduction of ZIF-8 to dynamic synthetic conditions allowed the new linker not only to substitute previous linkers but also to coordinate to sites that were formerly defective, increasing the overall linker content and decreasing specific surface area to the value expected for standard ZIF-8.…”

“…50 A recent report even invokes SALE as a method to fill defective ZIF-8 sites with new ligands. 51 Intuitively, it is feasible that the reintroduction of ZIF-8 to dynamic synthetic conditions allowed the new linker not only to substitute previous linkers but also to coordinate to sites that were formerly defective, increasing the overall linker content and decreasing specific surface area to the value expected for standard ZIF-8. PSDs further support this hypothesis with a sharp decrease in the unexpected pore at 7.2 Å in the linker-exchanged derivatives.…”

Defect-containing metal–organic framework materials for sensor applications

“…Reproduced with permission. 109 Copyright, 2023, Wiley-VCH. (f) CeTCPP-Au for US-triggered Au NP electron trapping, enhancing SDT for bacterial eradication and osteomyelitis detection.…”

“…2.2.4 Defect introduction via the ultrasonic-assisted method. In a study by Massahud and colleagues, 109 they explored the manipulation of MOF properties through defect engineering. However, achieving defects in ZIF-8 is challenging due to its stability.…”

“…(e) Schematic of the setup for acoustomicrofluidic defect creation. Reproduced with permission 109. Copyright, 2023, Wiley-VCH.…”