Stabilization of Pt nanoparticles within MOFs for selective hydrogenation of hazardous 4-nitrophenol to valuable 4-aminophenol: Confinement and synergistic effect

Nanocatalysts encapsulated in metal-organic frameworks: Size control and positive influences

Beyond traditional porous materials, metal-organic frameworks (MOFs) have attracted considerable attention for fabricating encapsulated nanocatalysts in the pores/cavities/channels of MOFs due to the high surface area, porous structure, and a large variety of organic linkers. As the host for nanocatalyst encapsulation, MOFs can provide uniform hierarchical pores and channels that can accelerate the mass transfer and migration of reactants or products and various metal‑oxygen clusters and organic linkers, which may interact strongly with nanocatalysts. Herein, state-of-the-art advancements in the encapsulation of nanocatalysts, including catalyst nanoparticles, clusters, quantum dots, and single-atom catalysts, have been summarized. The synthetic methods for nanocatalysts in MOFs and the enhanced properties are especially discussed. Then, positive effects upon the encapsulation of nanocatalysts in MOFs, including tunable chemical environment and encapsulation effects have been explored. Notably, the catalytic activity and product selectivity can be much improved by regulating the chemical environment around nanocatalysts and the interaction between the active nanocatalysts and metal nodes or organic linkers. Finally, challenges and future perspectives in encapsulated nanocatalysts in MOFs are proposed. This review could shed light on the construction of stable nanocatalysts encapsulation in MOFs with maximum exposed active sites and excellent activity in significant reactions.

Nanoarchitectured hyaluronic acid-decorated hierarchical drug-like assemblies as synergistic immune modulators against breast carcinoma

Considering the challenges of delivering drugs using nanoparticles, fabricating an intelligent drug-like nanocomposite platform with exceptional therapeutic effects has attracted enormous interest in achieving safe and highly effective tumor treatment. Although the activation of materials using external sources (light) is of great importance, it is obligatory to synergistically activate the internal stimuli, such as deadly free radicals and immune responses. This study aims to fabricate conformational biocompatible nanoassemblies based on in-situ grown platinum nanodots (Pt NDs) on the surface of manganese dioxide (MnO2) nanoflowers, followed by hyaluronic acid (HA) encapsulation (shortly HMP), enabling chemodynamic therapy (CDT), photothermal therapy (PTT), photothermal imaging, and immunotherapy synergistically. The HMP nanocomposites with enhanced photothermal conversion efficiency could deplete GSH in the tumor microenvironment, followed by the release of Mn2+ and Pt NDs. Mn2+ could further react with H2O2 to generate hydroxyl radicals (·OH) through a Fenton-like reaction, resulting in the CDT effect. The presence of Pt NDs showed an improvement in the photothermal conversion efficiency of HMP nanoassemblies (35.46 %) towards the PTT effect. In addition to synergistic (CDT and PTT) actions in 4 T1 cells in vitro, low doses of HMP nanocomposites could stimulate the high mobility group box 1 (HMGB-1) release and generate calreticulin (CRT) protein in tumor cells to provide necessary signals for immunotherapeutic destruction. Finally, HMP nanocomposites combined with light stimulation could effectively inhibit tumor growth in BALB/c tumor-bearing mice. In summary, the designed drug-free nanoassemblies resulted in enhanced tumor suppression through synergistic CDT, PTT, and potential immunotherapy therapeutic effects.

In-situ synthesis of sunlight-driven CuO-ZnO heterostructure photocatalyst for enhanced elimination of organic pollutants and CO2 reduction

Removing hazardous organic pollutants, such as 4-nitrophenol (4-NP) and Congo red (CR) dyes from aqueous media and CO2 from the atmospheric medium remains a significant challenge. Herein, we report a facile in-situ synthetic approach for fabricating CuO-ZnO heterostructure photocatalysts through the surfactant-assisted co-precipitation method. The catalytic results demonstrate that the Cu1O-ZnO photocatalyst exhibits excellent activity under direct sunlight irradiation, owing to the heterostructure formation between the CuO and ZnO. The Cu1O-ZnO photocatalyst showed higher reaction rate constant (k) values of 0.20 min-1 for 4-NP and 0.09 min-1 for CR compared to previous reports. Additionally, efficient CO2 reduction was also achieved over Cu1O-ZnO photocatalyst. The optical and structural characterization results indicate that the improved photocatalytic reduction and degradation observed for the Cu1O-ZnO photocatalyst can be attributed to the strong synergistic interaction between p-type CuO and n-type ZnO and the construction of the p-n heterojunction. As a result, the absorption of visible light distinctly increased and inhibited the recombination rate of the photo-created electron-hole (e-/h+). Furthermore, the Cu1O-ZnO photocatalyst exhibited remarkable durability and recyclability, retaining high photoactivity (≥ 93%) after five cycles, demonstrating its potential for real-world applications in the photocatalytic reduction and degradation reactions under direct sunlight irradiation.

Fabrication of silver nanoparticles decorated on sodium alginate microbeads enriched with keratin and investigation of its catalytic and antioxidant activity

In this study, an environmentally friendly, effective, easily synthesizable and recoverable nano-sized catalyst system (Ag@NaAlg-keratin) was designed by decorating Ag nanoparticles on microbeads containing sodium alginate (NaAlg) and keratin obtained from goose feathers. The structure, morphology and crystallinity of the Ag@NaAlg-keratin nanocatalyst were evaluated by XRD, FT-IR, FE-SEM, EDS/EDS mapping and TEM analyses. Catalytic ability of designed Ag@NaAlg-keratin nanocatalyst was then investigated against 4-nitrophenol (4-NP) and methyl orange (MO) reductions. Ag@NaAlg-keratin nanocatalyst effectively reduced 4-NP in 6 min and MO in 5 min, with rate constants of 0.17 min-1 and 0.16 min-1, respectively. Additionally, activation energies (Ea) were found as 39.8 kJ/mol for 4-NP and 37.9 kJ/mol for MO. Performed recyclability tests showed that the Ag@NaAlg-keratin nanocatalyst was easily recovered due to its microbead form and successfully reused five times, maintaining both its activity and structure. Furthermore, antioxidant activity of Ag@NaAlg-keratin nanocatalyst was the highest (73.16 %).

A Comprehensive Review on Adsorption, Photocatalytic and Chemical Degradation of Dyes and Nitro-Compounds over Different Kinds of Porous and Composite Materials

Dye and nitro-compound pollution has become a significant issue worldwide. The adsorption and degradation of dyes and nitro-compounds have recently become important areas of study. Different methods, such as precipitation, flocculation, ultra-filtration, ion exchange, coagulation, and electro-catalytic degradation have been adopted for the adsorption and degradation of these organic pollutants. Apart from these methods, adsorption, photocatalytic degradation, and chemical degradation are considered the most economical and efficient to control water pollution from dyes and nitro-compounds. In this review, different kinds of dyes and nitro-compounds, and their adverse effects on aquatic organisms and human beings, were summarized in depth. This review article covers the comprehensive analysis of the adsorption of dyes over different materials (porous polymer, carbon-based materials, clay-based materials, layer double hydroxides, metal-organic frameworks, and biosorbents). The mechanism and kinetics of dye adsorption were the central parts of this study. The structures of all the materials mentioned above were discussed, along with their main functional groups responsible for dye adsorption. Removal and degradation methods, such as adsorption, photocatalytic degradation, and chemical degradation of dyes and nitro-compounds were also the main aim of this review article, as well as the materials used for such degradation. The mechanisms of photocatalytic and chemical degradation were also explained comprehensively. Different factors responsible for adsorption, photocatalytic degradation, and chemical degradation were also highlighted. Advantages and disadvantages, as well as economic cost, were also discussed briefly. This review will be beneficial for the reader as it covers all aspects of dye adsorption and the degradation of dyes and nitro-compounds. Future aspects and shortcomings were also part of this review article. There are several review articles on all these topics, but such a comprehensive study has not been performed so far in the literature.