A trade-off between adsorption and photocatalysis over ZIF-derived composite

Coarse-grained force field for ZIF-8: A study on adsorption, diffusion, and structural properties

Metal-organic frameworks (MOFs) are revolutionizing a spectrum of industries, from groundbreaking gas storage solutions to transformative biological system applications. The intricate architecture of these materials necessitates the use of advanced computational techniques for a comprehensive understanding of their molecular structure and prediction of their physical properties. Coarse-grained (CG) simulations shine a spotlight on the often-neglected influences of defects, pressure effects, and spatial disorders on the performance of MOFs. These simulations are not just beneficial but indispensable for high-demand applications, such as mixed matrix membranes and intricate biological system interfaces. In this work, we propose an optimized CG force field tailored for ZIF-8. Our work provides a deep dive into sorption isotherms and diffusion coefficients of small molecules. We demonstrate the structural dynamics of ZIF-8, particularly how it responds to pressurization, which affects its crystal structure and leads to local changes in aperture size and area. Emphasizing the game-changing potential of CG simulations, we explore the characteristics of amorphization in ZIF-8. Through computational exploration, we aim to bridge the knowledge gap, enhancing the potential applications of nanoporous materials for various applications.

Accelerated cascade melanoma therapy using enzyme-nanozyme-integrated dissolvable polymeric microneedles

Dissolvable polymeric microneedles (DPMNs) have emerged as a powerful technology for the localized treatment of diseases, such as melanoma. Herein, we fabricated a DPMN patch containing a potent enzyme-nanozyme composite that transforms the upregulated glucose consumption of cancerous cells into lethal reactive oxygen species via a cascade reaction accelerated by endogenous chloride ions and external near-infrared (NIR) irradiation. This was accomplished by combining glucose oxidase (Gox) with a NIR-responsive chloroperoxidase-like copper sulfide (CuS) nanozyme. In contrast with subcutaneous injection, the microneedle system highly localizes the treatment, enhancing nanomedicine uptake by the tumor and reducing its systemic exposure to the kidneys and spleen. NIR irradiation further controls the potency and toxicity of the formulation by thermally disabling Gox. In a mouse melanoma model, this unique combination of photothermal, starvation, and chemodynamic therapies resulted in complete tumor eradication (99.2 ± 0.8 % reduction in tumor volume within 10 d) without producing signs of systemic toxicity. By comparison, other treatment combinations only resulted in a 42-76.5 % reduction in tumor growth. The microneedle patch design is therefore not only highly potent but also with regulated toxicity and improved safety.

Immobilization of iron phthalocyanine on MOF-derived N-doped carbon for promoting oxygen reduction in zinc-air battery

Functional carbon nanomaterials play a crucial role in the cathodic oxygen reduction reaction (ORR) for sustainable fuel cells and metal-air batteries. In this study, we propose an effective approach to immobilize iron phthalocyanines (FePc) by employing a porous N-doped carbon material, denoted as NC-1000, derived from a sheet-shaped coordination polymer. The resulting NC-1000 possesses substantial porosity and abundant pore defects. The nitrogen sites within NC-1000 not only facilitate FePc adsorption but also optimize the electron distribution at the Fe-N site. The FePc@NC-1000 composite material exhibits a significant number of active centers in the form of Fe-N4 moieties, showcasing satisfactory ORR activity. Specifically, it demonstrates an onset potential of 0.99 V, a positive half-wave potential of 0.86 V, a large limiting current of 5.96 mA cm-2, and a small Tafel slope of 44.41 mV dec-1. Additionally, theoretical calculations and experimental results confirm the favorable performance and durability of zinc-air batteries assembled using FePc@NC-1000, thereby highlighting their considerable potential for practical applications. Overall, this study provides a comprehensive exploration of the enhanced catalytic performance and increased stability of metal-organic framework-derived functional carbon nanomaterials as cost-effective, efficient, and stable catalysts for the ORR.

Activated carbon modified titanium dioxide/bismuth trioxide adsorbent: One-pot synthesis, high removal efficiency of organic pollutants, and good recyclability

Considerable endeavors have focused on tightly combining adsorption with photocatalysis in designing composite materials for environmental pollution treatment. Recent advances in coupling titanium dioxide/bismuth trioxide (TiO₂/Bi₂O₃) with activated carbon (AC) show significantly enhanced photocatalytic performance but face critical limitations including low adsorption capacity and multi-step synthesis. In this work, we introduce a one-pot synthesis of activated carbon modified TiO₂/Bi₂O₃ composite materials (TiO₂/Bi₂O₃/AC). Thanks to the integrated adsorbent/photocatalyst system, TiO₂/Bi₂O₃/AC shows a drastically enhanced removal efficiency for sulfamethazine (>81%), far beyond the corresponding value of the reported AC/TiO₂/Bi₂O₃ adsorbent (<40%). Notably, the removal rates of other typical pollutants including tetracyclines, methyl orange, and rhodamine B are as high as >98%. Furthermore, TiO₂/Bi₂O₃/AC obtains >80% of its adsorption rate for the fifth cycle after simple photo-regeneration without any other post-treatments. Kinetic analysis and photoelectric characterization are carried out to provide insight into adsorption mechanism. Therefore, this work demonstrates a considerable potential to design and construct other multifunctional adsorbents with advanced performance.

Gravity-driven rattan-based catalytic filter for rapid and highly efficient organic pollutant removal

Metal organic frameworks hold great promise as heterogeneous catalysts in sulfate radical (SO₄^∙-) based advanced oxidation. However, the aggregation of powdered MOF crystals and the complicated recovery procedure largely hinder their large-scale practical applications. It is important to develop eco-friendly and adaptable substrate-immobilized metal organic frameworks. Based on the hierarchical pore structure of the rattan, gravity-driven metal organic frameworks loaded rattan-based catalytic filter was designed to degrade organic pollutants by activating PMS at high liquid fluxes. Inspired by the water transportation of rattan, ZIF-67 was in-situ grown uniformly on the rattan channels inner surface using the continuous flow method. The intrinsically aligned microchannels in the vascular bundles of rattan acted as reaction compartments for the immobilization and stabilization of ZIF-67. Furthermore, the rattan-based catalytic filter exhibited excellent gravity-driven catalytic activity (up to 100 % treatment efficiency for a water flux of 10173.6 L·m^-2·h^-1), recyclability, and stability of organic pollutant degradation. After ten cycles, the TOC removal of ZIF-67@rattan was 69.34 %, maintaining a stable mineralisation capacity for pollutants. The inhibitory effect of the micro-channel promoted the interaction between active groups and contaminants, increasing the degradation efficiency and improving the stability of the composite. The design of a gravity-driven rattan-based catalytic filter for wastewater treatment provides an effective strategy for developing renewable and continuous catalytic systems.

Controlling C-C coupling in electrocatalytic reduction of CO2 over Cu1-xZnx/C

From the perspective of sustainable environment and economic value, the electroreduction of CO₂ to higher order multicarbon products is more coveted than that of C₁ products, owing to their higher energy densities and a wider applicability. However, the reduction process remains extremely challenging due to the bottleneck of C-C coupling over the catalyst surfaces, and therefore designing a suitable catalyst for efficient and selective electrocatalytic reduction of CO₂ is a need of the hour. With the target of producing C₃₊ products with higher selectivity, in this study we explored the nano-alloys of Cu_1-xZn_x as electrocatalysts for CO₂ reduction. The nano-alloy Cu_1-xZn_x synthesized from the corresponding bimetallic metal organic framework materials demonstrated a gradual enhancement in the selectivity of acetone upon CO₂ electroreduction with higher doping of Zn. The Cu_1-xZn_x alloy opened up a wide possibility of fine-tuning the electronic structure by shifting the position of the d-band centre and modulating the interaction with intermediate CO and thus enhanced the selectivity of desirable products, which might not have been accessible otherwise. The postulated molecular mechanism of CO₂ electroreduction involving the desorption of the poorly adsorbed intermediate CO due to the presence of Zn and spilling over of free CO to Cu sites in the nano-alloy Cu_1-xZn_x for further C-C coupling to yield acetone was corroborated by the first principles studies.

MOF-derived N-doped ZnO carbon skeleton@hierarchical Bi2MoO6 S-scheme heterojunction for photodegradation of SMX: Mechanism, pathways and DFT calculation

Semiconductor photocatalytic degradation of pollutants is considered to be one of the promising sustainable energy routes. Nevertheless, it is challenging for photocatalysts to have excellent visible light absorption and suppress photo-generated electron-hole recombination at the same time. Here, we prepared nitrogen-doped ZnO carbon skeleton by directly calcining the metal-organic framework. Then hierarchical Bi₂MoO₆ nanosheets are grown in situ on its surface to synthesize S-scheme heterojunction. This special 3D layered and oxygen vacancies work together to make photo-generated electrons and holes easier to separate and migrate. Therefore, the pseudo-first-order kinetic constant of N-doped ZnO carbon skeleton@Bi₂MoO₆ degradation of sulfamethoxazole reaches 0.022 min^-1, which is almost 10 times that of ZIF-8 derived ZnO and 27.5 times Bi₂MoO₆ under visible light irradiation. Meanwhile, the mechanism of driving charge transfer of S-scheme heterojunction, and the photocatalytic degradation pathway of sulfamethoxazole are also analyzed. This work will provide a new way to construct S-scheme heterojunction photocatalyst to degrade antibiotic pollutants.

The role of synthesis vis-à-vis the oxygen vacancies of Co3O4 in the oxygen evolution reaction

The combustion synthesized Co3O4 due to high oxygen vacancies exhibited a significant oxygen evolution reaction as has been probed by electrocatalytic experiments and DFT calculations.

Synthesis of dihydropyrimidinones via multicomponent reaction route over acid functionalized Metal-Organic framework catalysts

Multi component reactions over heterogeneous solid acid catalysts are extremely important owing to easy separation, amenable recycling, and prospective scaling up of the process. Here, we are reporting the synthesis of biologically important dihydropyrimidinones over postsynthetic modified Cr-based metal-organic framework materials as heterogeneous catalysts containing the bifunctional Lewis and Brønsted acid sites. Cr-based metal-organic frameworks contained coordinatively unsaturated metal sites as inherent Lewis acid sites, whereas postsynthetic modifications introduced the Brønsted acid sites in the framework. A direct one pot synthesis route was employed to produce the pristine MOF in pure aqueous medium without using any additives. The bulk structure, morphology, surface and bonding properties of the synthesized materials were thoroughly characterized with powder XRD, FTIR, XPS, FE-SEM, TGA, and N₂ sorption isotherms. A qualitative evolution of acid strength was carried out over the functionalized MOFs. Among the post synthetic functionalized materials, carboxylic acid functionalized framework exhibited a very high yield of dihydropyrimidinones under solvent less moderate reaction conditions. The catalyst also demonstrated a robust recyclability and wide substrate scope. Comparative study showed a very high catalytic activity of the postsynthetic modified MOFs in comparison to the reported literature. The reaction condition was optimized by varying parameters like solvent, temperature, reaction duration and catalyst loadings. The mechanistic studies indicated the involvement of both the Lewis and Brønsted sites acid sites of the catalysts in the multicomponent reaction.

Core-shell ZIF-8@MIL-68(In) derived ZnO nanoparticles-embedded In2O3 hollow tubular with oxygen vacancy for photocatalytic degradation of antibiotic pollutant

Developing a novel core-multishelled metal oxide hollow tube with rich oxygen vacancy is highly attractive in photocatalytic degradation of antibiotic pollutant. Herein, ZnO@In₂O₃ core-shell hollow microtubes were synthesized via one-step calcination of ZIF-8@MIL-68(In) formed by an in-situ self-assembly. TEM images demonstrate that 0D ZnO quantum dots (QDs) shell with 0.2 µm were well coated on the surface of 1D In₂O₃ hollow tube as the core with 1.2 µm. The synthesized heterostructure indicates the enhanced photocatalytic performance in tetracycline (TC) degradation compared with single ZIF-derived ZnO and MIL-68(In)-derived In₂O₃ under simulated solar irradiation. Besides, organic pollutants including malachite green (MG), methylene blue (MB) and rhodamine B (RhB) are further used to evaluate the photocatalytic activity of ZnO@In₂O₃, and the effect of weight ratios between ZnO and In₂O₃ on degradation efficiency is also studies. The ZnO@In₂O₃ heterojunction can provide higher specific surface area, expose more active sites, possess appropriate number of oxygen vacancies, enhance light absorption and further effectively boost the transfer and separation of photoinduced charge carriers. In addition, the proposed photocatalytic mechanism and degradation pathway are discussed in detail based on active species trapping test, electron spin resonance (ESR) and LCMS.

Recyclable ZnS QDs as an efficient photocatalyst for dye degradation under the UV and visible light

Energy-efficient synthesized ZnS QDs with unique visible range absorption through defects show the best photocatalytic activity under UV light and best degradation under visible light.