Harvesting mechanical energy for hydrogen generation by piezoelectric metal-organic frameworks

Metal-Organic Framework Nanomaterials as a Medicine for Catalytic Tumor Therapy: Recent Advances

Nanomaterials, with unique physical, chemical, and biocompatible properties, have attracted significant attention as an emerging active platform in cancer diagnosis and treatment. Amongst them, metal-organic framework (MOF) nanostructures are particularly promising as a nanomedicine due to their exceptional surface functionalities, adsorption properties, and organo-inorganic hybrid characteristics. Furthermore, when bioactive substances are integrated into the structure of MOFs, these materials can be used as anti-tumor agents with superior performance compared to traditional nanomaterials. In this review, we highlight the most recent advances in MOFs-based materials for tumor therapy, including their application in cancer treatment and the underlying mechanisms.

Magnetostrictive-piezocatalytic CoFe2O4@UiO-66 nanohybrid and its potential for deep-seated tumor treatment

Magnetostrictive CoFe2O4 (CFO) nanoparticles were encapsulated within a UiO-66 metal-organic-framework layer to form a CFO@UiO-66 nanohybrid. The deforming of CFO, in response to a high-frequency AC magnetic field, initiates the piezocatalytic property of UiO-66 to generate ˙OH radicals, which can kill cancer cells buried in thick tissues, showcasing bright potential for deep-seated tumor treatment.

Mechanically Enhanced Detoxification of Chemical Warfare Agent Simulants by a Two-Dimensional Piezoresponsive Metal-Organic Framework

Chemical warfare agents (CWAs) refer to toxic chemical substances used in warfare. Recently, CWAs have been a critical threat for public safety due to their high toxicity. Metal-organic frameworks have exhibited great potential in protecting against CWAs due to their high crystallinity, stable structure, large specific surface area, high porosity, and adjustable structure. However, the metal clusters of most reported MOFs might be highly consumed when applied in CWA hydrolysis. Herein, we fabricated a two-dimensional piezoresponsive UiO-66-F4 and subjected it to CWA simulant dimethyl-4-nitrophenyl phosphate (DMNP) detoxification under sonic conditions. The results show that sonication can effectively enhance the removal performance under optimal conditions; the reaction rate constant k was upgraded 45% by sonication. Moreover, the first-principle calculation revealed that the band gap could be further widened with the application of mechanical stress, which was beneficial for the generation of 1O2, thus further upgrading the detoxification performance toward DMNP. This work demonstrated that mechanical vibration could be introduced to CWA protection, but promising applications are rarely reported.

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.

Tunable zirconium-based metal organic frameworks synthesis for dibutyl phthalate efficient removal: An investigation of adsorption mechanism on macro and micro scale

The tunable porous structure of metal organic frameworks (MOFs) plays a crucial role in determining their adsorption performance. In this study, we developed and employed a strategy involving monocarboxylic acid assistance to synthesize a series of zirconium-based MOFs (UiO-66-F4) for the removal of aqueous phthalic acid esters (PAEs). The adsorption mechanisms were investigated by combining batch experiments, characterization and theoretical simulation. By adjusting the affecting factors (i.e., initial concentration, pH values, temperature, contact time and interfering substance), the adsorption behavior was confirmed as a spontaneous and exothermic chemisorption process. The Langmuir model provided a good fit, and the maximum expected adsorption capacity of di-n-butyl phthalate (DnBP) on UiO-66-F4(PA) was calculated to be 530.42 mg·g-1. Besides, through carrying out the molecular dynamics (MD) simulation, the multistage adsorption process in the form of DnBP clusters was revealed on a microcosmic scale. The independent gradient model (IGM) method showed the types of weak interactions of inter-fragments or between DnBP and UiO-66-F4. Furthermore, the synthesized UiO-66-F4 displayed excellent removal efficiency (>96 % after 5 cycles), satisfactory chemical stability and reusability in the regeneration process. Hence, the modulated UiO-66-F4 will be regarded as a promising adsorbent for PAEs separation. This work will provide referential significance in tunable MOFs development and actual applications of PAEs removal.

Piezoelectric Metal-Organic Frameworks Based Sonosensitizer for Enhanced Nanozyme Catalytic and Sonodynamic Therapies

The regulation of electrostatic electric fields through electrical stimulation is an efficient method to increase the catalytic activity of nanozymes and improve the therapeutic effect of nanozyme catalytic therapy. Piezoelectric materials, which are capable of generating a built-in electric field under ultrasound (US), not only improve the activity of nanozymes but also enable piezoelectric sonodynamic therapy (SDT). In this study, a sonosensitizer based on a Hf-based metal-organic framework (UIO-66) and Au nanoparticles (NPs) was produced. Under US irradiation, UIO-66 can generate a built-in electric field inside the materials, which promotes electron-hole separation and produces reactive oxygen species (ROS). The introduction of Au NPs facilitated the electron transfer, which inhibited the recombination of the electron-hole pairs and improved the piezoelectric properties of UIO-66. The value of the piezoelectric constant (d₃₃) increased from 71 to 122 pmV^-1 after the deposition of Au NPs. In addition, the intrinsic catalase and peroxidase activities of the Au NPs were increased 2-fold after the stimulation from the built-in electric field induced through US exposure. In vivo and in vitro experiments revealed that the proposed sonosensitizer can kill cancer cells and inhibit tumor growth in mice through the enhanced piezoelectric SDT and nanozyme catalytic therapy. The piezoelectric sensitizer proposed in this work proved to be an efficient candidate that can be used for multiple therapeutic modalities in tumor therapy.

Modulating the metal center in MIL-101 for the piezoelectric catalytic synthesis of hydrogen peroxide

Modulation of metal centers is a promising strategy to boost catalytic performance. Two structurally identical MOFs with different metal centers, namely MIL-101(Cr) and MIL-101(Fe), were synthesized. MIL-101(Cr) exhibits superior H₂O₂ yield due to Cr's electron-donating ability. This work helps in developing the rational design and optimization of MOF catalysts for catalytic reactions.

Bi-MOFs with two different morphologies promoting degradation of organic dye under simultaneous photo-irradiation and ultrasound vibration treatment

For the first time, piezocatalysis activity has been observed in bismuth-based MOFs (ultrasound vibration treatment) with two different morphologies, namely FCAU-17 (flakes) and CAU-17 (rods). CAU-17 and FCAU-17 were synthesized by solvothermal and ultrasonic methods, respectively, with the same organic ligand (1,3,5-benzenetricarboxylic acid) and metal salt (Bi(NO₃)₃·5H₂O). Among these, the apparent rate constant k of CAU-17 in piezo-photocatalysis is 3.9 × 10^-2 min^-1, which is ∼3.9 and ∼ 1.5 times of those in photocatalysis and piezocatalysis, respectively. CAU-17 showed much high piezo-photocatalytic activity during degradation of RhB. Efficiently coupling between piezocatalysis and photocatalysis has been realized in rod-like CAU-17 (ultrasound vibration treatment). Our results provide a new strategy to improve catalytic performance of Bi MOFs through an efficient synergistic piezo-photocatalysis approach for environmental remediation.

Piezoelectric polarization of MIL-100(Fe) by harvesting mechanical energy for cocatalyst-free H2 evolution

To suit the emergency of a new strategy for hydrogen (H2) evolution, a metal–organic framework (MIL-100(Fe)) is applied in the piezoelectric-driven process for catalytic H2 generation. Herein, MIL-100(Fe) was firstly...