The Atomic Structure and Mechanical Properties of ZIF-4 under High Pressure: Ab Initio Calculations

Controllable ion design in flexible metal organic framework film for performance regulation of electrochemical biosensing

The limitations of solvent residues, unmanageable film growth regions, and substandard performance impede the extensive utilization of metal-organic framework (MOF) films for biosensing devices. Here, we report a strategy for ion design in gas-phase synthesized flexible MOF porous film to attain universal regulation of biosensing performances. The key fabrication process involves atomic layer deposition of induced layer coupled with lithography-assisted patterning and area-selective gas-phase synthesis of MOF film within a chemical vapor deposition system. Sensing platforms are subsequently formed to achieve specific detection of H2O2, dopamine, and glucose molecules by respectively implanting Co, Fe, and Ni ions into the network structure of MOF films. Furthermore, we showcase a practical device constructed from Co ions-implanted ZIF-4 film to accomplish real-time surveillance of H2O2 concentration at mouse wound. This study specifically elucidates the electronic structure and coordination mode of ion design in MOF film, and the obtained knowledge aids in tuning the electrochemical property of MOF film for advantageous sensing devices.

Deciphering the controlling factors for phase transitions in zeolitic imidazolate frameworks

Zeolitic imidazolate frameworks (ZIFs) feature complex phase transitions, including polymorphism, melting, vitrification, and polyamorphism. Experimentally probing their structural evolution during transitions involving amorphous phases is a significant challenge, especially at the medium-range length scale. To overcome this challenge, here we first train a deep learning-based force field to identify the structural characteristics of both crystalline and non-crystalline ZIF phases. This allows us to reproduce the structural evolution trend during the melting of crystals and formation of ZIF glasses at various length scales with an accuracy comparable to that of ab initio molecular dynamics, yet at a much lower computational cost. Based on this approach, we propose a new structural descriptor, namely, the ring orientation index, to capture the propensity for crystallization of ZIF-4 (Zn(Im)2, Im = C3H3N2-) glasses, as well as for the formation of ZIF-zni (Zn(Im)2) out of the high-density amorphous phase. This crystal formation process is a result of the reorientation of imidazole rings by sacrificing the order of the structure around the zinc-centered tetrahedra. The outcomes of this work are useful for studying phase transitions in other metal-organic frameworks (MOFs) and may thus guide the development of MOF glasses.

The antibacterial activity of three zeolitic-imidazolate frameworks and zinc oxide nanoparticles derived from them

Zinc has been widely studied for its antibacterial properties due to its low toxicity, availability, and low cost. This research focused on analysing the antibacterial effects of three types of MOFs (metal-organic frameworks) with zinc as the central metal: ZIF-4, ZIF-7, and ZIF-8. The study found that ZIF-8 had the strongest antibacterial effect, while ZIF-7 had the weakest among them. These findings were consistent with the results of the ICP (inductively coupled plasma) analysis, which measured the amount of zinc released. Additionally, the antibacterial effect of ZIF-8 was found to be higher than that of zinc oxide species obtained from calcination of the compounds. Among the zinc oxide samples, ZnO nanoparticles which derived from ZIF-4 showed the highest antibacterial activity.