Molecular Encapsulation beyond the Aperture Size Limit through Dissociative Linker Exchange in Metal–Organic Framework Crystals

Abstract

Under linker exchange conditions, large guests with molecular diameters 3-4 times the framework aperture size have been encapsulated into preformed nanocrystals of the metal-organic framework ZIF-8. Guest encapsulation is facilitated by the formation of short-lived "open" states of the pores upon linker dissociation. Kinetic studies suggested that linker exchange reactions in ZIF-8 proceed via a competition between dissociative and associative exchange mechanisms, and guest encapsulation was enhanced under conditions where the dissociative pathway predominates.

Magnetic MOF microreactors for recyclable size-selective biocatalysis

“…S17†) so these are expected to be excluded by the micropores of the capsule shell. While two recent reports suggest that oversize molecules such as caffeine 32 and Rhodamine 6G 33 can be encapsulated by ZIF-8 arising from framework expansion or dissociative linker exchange mechanisms, it is most likely that 4–6 pass through very small pin-hole defects within the dense microporous ZIF-8 outer layer which is responsible for the observed albeit very low activity.…”

Selective Surface PEGylation of UiO-66 Nanoparticles for Enhanced Stability, Cell Uptake, and pH-Responsive Drug Delivery

“…Thus, drug-delivery systems have become one of the most promising applications for health care 4, 5, 6. A large number of strategies have been studied, but for application, drug-delivery systems must overcome issues surrounding bioavailability,7, 8 the uncontrollable release of drugs (usually due to carrier instability),9, 10, 11 loading capacities,11, 12, 13 particle size,14, 15, 16 nanoparticle cellular internalization routes,14, 17, 18 and toxicity 19, 20. The exceptional storage capacities of metal-organic frameworks (MOFs), together with their robustness and structural tailorability, have made them attractive for a wide variety of applications,21, 22 including several promising breakthroughs in biomedicine 9, 10, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33.…”

Encapsulation of Single Plasmonic Nanoparticles within ZIF‐8 and SERS Analysis of the MOF Flexibility

“…Interestingly, there is some controversy in the literature related to the incorporation of guest molecules into MOFs by diffusion. In general, the diffusion of guest molecules is limited to those that are smaller than the MOF aperture size, but it has been occasionally reported that molecules larger that both aperture and pore sizes can be successfully incorporated . Recent adsorption and diffusion studies of a series of probe molecules have demonstrated the framework flexibility of ZIF‐8, finding a molecular sieving effect in the molecular size range of 4–6 Å …”