A Method for Determining Incorporation Depth in Core-Shell UiO-66 Nanoparticles Synthesized Via Postsynthetic Exchange.

Postsynthetic exchange (PSE) is a key technique for integrating sensitive linkers into metal-organic frameworks (MOFs). Despite its importance, investigations into linker distributions have primarily focused on micrometer-sized crystals due to the analytical limitations, leaving nanoparticles less explored, although they are commonly synthesized and used in applications. In particular, the emergence of core-shell nanostructures via PSE has shown potential for applications in CO2 adsorption and selective catalysis. This study addresses this gap by investigating the formation of core-shell structures on nanoparticles under diffusion-controlled PSE conditions. By analyzing volume-to-surface ratios and conducting time-dependent experiments, we confirmed that these conditions facilitate the development of core-shell architectures. We also developed a straightforward method to calculate the minimum incorporation depth using basic parameters such as particle size and the total amount of incorporated linker. The accuracy of our approach was validated against data obtained from transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy. These findings enhance the understanding of PSE in MOF nanoparticles and open up promising avenues for developing advanced MOF core-shell structures for various applications.

Development of high refractive index UiO-66 framework derivatives via ligand halogenation.

UiO-66 is a Zr-based metal-organic framework (MOF) with exceptional chemical and thermal stability. The modular design of a MOF allows the tuning of its electronic and optical properties to obtain tailored materials for optical applications. Making use of the halogenation of the 1,4-benzenedicarboxylate (bdc) linker, the well-known monohalogenated UiO-66 derivatives were examined. In addition, a novel diiodo bdc based UiO-66 analogue is introduced. The novel UiO-66-I2 MOF is fully characterized experimentally. By applying density functional theory (DFT), fully relaxed periodic structures of the halogenated UiO-66 derivatives are generated. Subsequently, the HSE06 hybrid DFT functional is used to calculate the electronic structures and optical properties. The obtained band gap energies are validated with UV-Vis measurements to assure a precise description of the optical properties. Finally, the calculated refractive index dispersion curves are evaluated underlining the capabilities to tailor the optical properties of MOFs by linker functionalization.

Correction: Tuning the optical properties of the metal-organic framework UiO-66 via ligand functionalization.

Correction for 'Tuning the optical properties of the metal-organic framework UiO-66 via ligand functionalization' by Marvin Treger et al., Phys. Chem. Chem. Phys., 2023, 25, 6333-6341, https://doi.org/10.1039/D2CP03746G.

Tuning the optical properties of the metal-organic framework UiO-66 via ligand functionalization.

Metal-organic frameworks (MOFs) are a promising class of materials for optical applications, especially due to their modular design which allows fine-tuning of the relevant properties. The present theoretical study examines the Zr-based UiO-66-MOF and derivatives of it with respect to their optical properties. Starting from the well-known monofunctional amino- and nitro-functionalized UiO-66 derivatives, we introduce novel UiO-66-type MOFs containing bifunctional push-pull 1,4-benzenedicarboxylate (bdc) linkers. The successful synthesis of such a novel UiO-66 derivative is also reported. It was carried out using a para-nitroaniline (PNA)-based bdc-analogue linker. Applying density functional theory (DFT), suitable models for all UiO-66-MOF analogues were generated by assessing different exchange-correlation functionals. Afterwards, HSE06 hybrid functional calculations were performed to obtain the electronic structures and optical properties. The detailed HSE06 electronic structure calculations were validated with UV-Vis measurements to ensure reliable results. Finally, the refractive index dispersion of the seven UiO-66-type materials is compared, showing the possibility to tailor the optical properties by the use of functionalized linker molecules. Specifically, the refractive index can be varied over a wide range from 1.37 to 1.78.

Transmission Porosimetry Study on High-quality Zr-fum-MOF Thin Films.

Crystalline Zr-fum-MOF (MOF-801) thin films of high quality are prepared on glass and silicon substrates by direct growth under solvothermal conditions. The synthesis is described in detail and the influence of different synthesis parameters such as temperature, precursor concentration, and the substrate type on the quality of the coatings is illustrated. Zr-fum-MOF thin films are characterized in terms of crystallinity, porosity, and homogeneity. Dense films of optical quality are obtained. The sorption behavior of the thin films is studied with various adsorptives. It can be easily monitored by measuring the transmission of the films in gas flows of different compositions. This simple transmission measurement at only one wavelength allows a very fast evaluation of the adsorption properties of thin films as compared to traditional sorption methods. The sorption behavior of the thin films is compared with the sorption properties of Zr-fum-MOF powder samples.