A metal-organic framework-integrated composite for piezocatalysis-assisted tumour therapy: design, related mechanisms, and recent advances

With the growing need for more effective tumour treatment, piezocatalytic therapy has emerged as a promising approach due to its distinctive capacities to generate ROS through stress induction and regulate the hypoxic state of the TME. MOF-based piezocatalysts not only possess the benefits of piezocatalysis but also exhibit several advantages associated with MOFs, such as tunable pore size, large specific surface area, and good biocompatibility. Therefore, they are expected to become a powerful promoter of piezocatalytic therapy. This review elaborates on the fundamental principles of piezocatalysis and summarises recent advances in the piezocatalytic therapy and combination therapies of tumours, generalising the strategies for constructing piezocatalytic systems based on MOFs. Finally, the challenges confronted and future opportunities for the design and application of piezocatalytic MOF anticancer systems have been discussed.

Multivariate metal-organic frameworks generated through post-synthetic modification: impact and future directions

Reticular chemistry has proven to be invaluable over time, thanks to the structural versatility, and tailored porosity observed in structures like metal-organic frameworks (MOFs), covalent-organic frameworks (COFs), and metal-organic polyhedra (MOPs). Despite the wide array of ligands and metals available for synthesizing MOFs, they are still somewhat constrained by the reliance on de novo conditions and the focus on generating MOFs with single ligand and metal. To surpass these limitations, researchers have established strategies to generate multivariate (MTV) MOF structures incorporating more than one ligand/metal into the crystal lattice. MTV-MOFs have demonstrated enhanced properties by virtue of the additional functionalities incorporated within their structures. One approach to developing MTV-MOFs is through post-synthetic modification (PSM), where new functionalities are introduced after the initial synthesis, thereby achieving the enhanced properties of MTV-MOFs even in cases where the new functionalities are incompatible with MOF synthesis.

A Strategy to Enhance the Ferroelectric Behavior of MOF-802(Hf) via Doping Zr4+ Ions

MOF ferroelectrics, as a crucial member of molecular ferroelectrics, have shown intriguing advantages owing to the designability of structures and tunability of physicochemical properties, which make them an appealing group of ferroelectric materials. However, the weak ferroelectric property still is a huge challenge for further development. Here, a series of Zr-doped MOF-802(Hf)s were successfully synthesized through doping Zr⁴⁺ ions into the parent MOF-802(Hf) to improve ferroelectric properties. The well-shaped P-E hysteresis loops of Zr-doped MOF-802(Hf)s illustrate their ferroelectricity, and ferroelectric properties are effectively enhanced compared with the parent MOF-802(Hf). What's more, remanent polarization reaches 0.511 μC/cm² when the concentration of Zr⁴⁺ ions is 5%, which is 5 times higher than that of the parent MOF-802(Hf) and is on par with some perovskite ferroelectrics. The increased ferroelectric performance is attributed to the enhanced polarity of the whole structure triggered by lattice distortion when Hf⁴⁺ ions of the parent MOF-802(Hf) are substituted by Zr⁴⁺ ions. As far as we know, this is the first report on Hf-MOF exhibiting improved ferroelectric behaviors through doping metal ions into lattice nodes. This work demonstrates that introducing the second metal ions into lattice nodes of MOFs is an efficacious approach for exploiting MOF ferroelectrics with superior performance.

Effective Enhancement of the Ferroelectric Performance of Polar Co-Gallate MOF by Doping M2+ Ions (M = Mg, Mn, Ni) into Framework Nodes

MOF ferroelectrics have been demonstrated to be a promising candidate owing to various structures and controllable properties. However, weak ferroelectricity hampers their boom. Herein, a convenient strategy, doping metal ions into the framework nodes of parent MOF, is adopted to enhance ferroelectric performance. A series of M-doped Co-Gallate (M = Mg, Mn, Ni) were synthesized to improve ferroelectric properties. The electrical hysteresis loop demonstrated its ferroelectric behaviors, exhibiting obviously improved ferroelectric properties compared with the parent Co-Gallate. The remanent polarization was enhanced by two times for Mg-doped Co-Gallate, six times for Mn-doped Co-Gallate, and four times for Ni-doped Co-Gallate. The promoted ferroelectric performances are ascribed to the enhanced polarity of the overall structure triggered by framework distortion. Intriguingly, ferroelectric behaviors increase in the order Mg < Ni < Mn, displaying the same tendency as the difference value in the ionic radius between Co²⁺ ions and M²⁺ metal ions (M = Mg, Mn, Ni). These results demonstrate doping of metal ions is a valid strategy to enhance ferroelectric performances, which may serve as a guide in modulating ferroelectric behaviors.

Photo-Induced Preparation of Ag@MOF-801 Composite Based Heterogeneous Nanocatalyst for the Production of Biodiesel

Hybrid materials based on metal-organic frameworks (MOFs) and nanoparticles (NPs) have gained considerable popularity in a variety of applications. Particularly, these types of materials have demonstrated excellent efficiency in heterogeneous catalysis due to the synergistic effect between the components. Herein, we report a simple, eco-friendly, photocatalytic method for the fabrication of Zr containing MOF-801 and a silver (Ag) NPs-based hybrid (Ag@MOF-801). In this method, the photocatalytic property of the central metal ion (Zr) of MOF was exploited to promote the formation and deposition of Ag NPs on the surface of the MOF-801 under the irradiation of visible light. The successful incorporation of Ag NPs was ascertained by powder X-ray diffraction (XRD) and UV-Vis analysis, while the morphology and surface area of the sample was determined by N2 adsorption–desorption and scanning electron microscopy (SEM), respectively. The resulting Ag@MOF-801 hybrid served as a highly efficient catalyst for the transesterification of used vegetable oil (UVO) for the production of biodiesel. The Ag@MOF-801 catalyst exhibited superior catalytic activity compared to its pristine MOF-801 counterpart due to the enhanced surface area of the material.