An Appraisal for Providing Charge Transfer (CT) Through Synthetic Porous Frameworks for their Semiconductor Applications

In recent years, there has been considerable focus on the development of charge transfer (CT) complex formation as a means to modify the band gaps of organic materials. In particular, CT complexes alternate layers of aromatic molecules with donor (D) and acceptor (A) properties to provide inherent electrical conductivity. In particular, the synthetic porous frameworks as attractive D-A components have been extensively studied in recent years in comparison to existing D-A materials. Therefore, in this work, the synthetic porous frameworks are classified into conjugated microporous polymers (CMPs), covalent organic frameworks (COFs), and metal-organic frameworks (MOFs) and compare high-quality materials for CT in semiconductors. This work updates the overview of the above porous frameworks for CT, starting with their early history regarding their semiconductor applications, and lists CT concepts and selected key developments in their CT complexes and CT composites. In addition, the network formation methods and their functionalization are discussed to provide access to a variety of potential applications. Furthermore, several theoretical investigations, efficiency improvement techniques, and a discussion of the electrical conductivity of the porous frameworks are also highlighted. Finally, a perspective of synthetic porous framework studies on CT performance is provided along with some comparisons.

Advances in 2D Materials Based Gas Sensors for Industrial Machine Olfactory Applications

The escalating development and improvement of gas sensing ability in industrial equipment, or "machine olfactory", propels the evolution of gas sensors toward enhanced sensitivity, selectivity, stability, power efficiency, cost-effectiveness, and longevity. Two-dimensional (2D) materials, distinguished by their atomic-thin profile, expansive specific surface area, remarkable mechanical strength, and surface tunability, hold significant potential for addressing the intricate challenges in gas sensing. However, a comprehensive review of 2D materials-based gas sensors for specific industrial applications is absent. This review delves into the recent advances in this field and highlights the potential applications in industrial machine olfaction. The main content encompasses industrial scenario characteristics, fundamental classification, enhancement methods, underlying mechanisms, and diverse gas sensing applications. Additionally, the challenges associated with transitioning 2D material gas sensors from laboratory development to industrialization and commercialization are addressed, and future-looking viewpoints on the evolution of next-generation intelligent gas sensory systems in the industrial sector are prospected.

Twinned crystal Cd0.9Zn0.1S/MoO3 nanorod S-scheme heterojunctions as promising photocatalysts for efficient hydrogen evolution

Leveraging solar energy through photocatalytic hydrogen production from water stands out as one of the most promising approaches to address the energy and environmental challenges. The choice of catalyst profoundly influences the outcomes of photocatalytic reactions, and constructing heterojunctions has emerged as a widely applied strategy to overcome the limitations associated with single-phase photocatalysts. MoO3, renowned for its high chemical stability, encounters issues such as low photocatalytic efficiency and fast recombination of photogenerated electrons and holes. To tackle these challenges, the morphology of MoO3 has been controlled to form nanorods, simultaneously suppressing the aggregation of the catalyst and increasing the number of surface-active sites. Moreover, to facilitate the separation of photogenerated charge carriers, Cd0.9Zn0.1S nanoparticles with a twin crystal structure are deposited on the surface of MoO3, establishing an S-scheme heterojunction. Experimental findings demonstrate that the synergistic effects arising from the well-defined morphology and interface interactions extend the absorption range to visible light response, improve charge transfer activity, and prolong the lifetime of charge carriers. Consequently, Cd0.9Zn0.1S/MoO3 S-scheme heterojunctions exhibit outstanding photocatalytic hydrogen production performance (3909.79 μmol g-1 h-1) under visible light irradiation, surpassing that of MoO3 by nearly nine fold.

Metal-Organic Frameworks-Derived Nanocarbon Materials and Nanometal Oxides for Photocatalytic Applications

Harnessing low-density solar energy and converting it into high-density chemical energy through photocatalysis has emerged as a promising avenue for the production of chemicals and remediation of environmental pollution, which contributes to alleviating the overreliance on fossil fuels. In recent years, metal-organic frameworks (MOFs) have gained widespread application in the field of photocatalysis due to their photostability, tunable structures, and responsiveness in the visible light range. However, most MOFs exhibit relatively low response to light, limiting their practical applications. MOFs-derived nanomaterials not only retain the inherent advantages of pristine MOFs but also show enhanced light adsorption and responsiveness. This review categorizes and summarizes MOFs-derived nanomaterials, including nanocarbons and nanometal oxides, providing representative examples for the synthetic strategies of each category. Subsequently, the recent research progress on MOFs-derived materials in photocatalytic applications are systematically introduced, specifically in the areas of photocatalytic water splitting to H2, photocatalytic CO2 reduction, and photocatalytic water treatment. The corresponding mechanisms involved in each photocatalytic reaction are elaborated in detail. Finally, the review discusses the challenges and further directions faced by MOFs-derived nanomaterials in the field of photocatalysis, highlighting their potential role in advancing sustainable energy production and environmental remediation.

Manipulation of interfacial charge dynamics for metal-organic frameworks toward advanced photocatalytic applications

Compared to other known materials, metal-organic frameworks (MOFs) have the highest surface area and the lowest densities; as a result, MOFs are advantageous in numerous technological applications, especially in the area of photocatalysis. Photocatalysis shows tantalizing potential to fulfill global energy demands, reduce greenhouse effects, and resolve environmental contamination problems. To exploit highly active photocatalysts, it is important to determine the fate of photoexcited charge carriers and identify the most decisive charge transfer pathway. Methods to modulate charge dynamics and manipulate carrier behaviors may pave a new avenue for the intelligent design of MOF-based photocatalysts for widespread applications. By summarizing the recent developments in the modulation of interfacial charge dynamics for MOF-based photocatalysts, this minireview can deliver inspiring insights to help researchers harness the merits of MOFs and create versatile photocatalytic systems.

Synthesis of cellulose cotton-based UiO-66 MOFs for the removal of rhodamine B and Pb(II) metal ions from contaminated wastewater

The presence of pollutants in drinking water has become a significant concern recently. Various substances, including activated carbon, membranes, biochar, etc., are used to remove these pollutants. In the present study, a new composite comprising cotton fabric and a mixture of Metal-Organic Frameworks (MOFs) was synthesized and used as an adsorbent for eliminating pollutants from wastewater. At first, the UiO-66 MOFs were prepared by a simple method of reacting Zirconium (IV) chloride (ZrCl4) and p-Phthalic acid (PTA) after successful preparation of UiO-66 then modified its surface with amino functional groups by reacting with APTES to obtain UiO-66-NH2. Moreover, the cellulose cotton fabric (CF) surface was modified with Polydopamine (PDA) and obtained CF@PDA. Further, with the help of EDC-HCl and NHS, the UiO-66-NH2 grafted on the surface of the CF@PDA and finally obtained CF@PDA/UiO-66-NH2. In addition, the adsorption study was performed toward RhB dye and Pb(II) metal ion pollutants. The maximum adsorption toward RhB dye was 68.5 mg/g, while toward Pb(II) metal ions was 65 mg/g. In addition, the kinetic study was also conducted and the result favoured the Pseudo-second order kinetic study. The adsorption isotherm was also studied and the Langmuir model was more fitted as compared with the Freundlich model. Moreover, the material has excellent regeneration and recycling ability after ten cycles. The significant adsorption ability, the novel combination of cotton and MOFs, and the recycling feature make our material CF@PDA/UiO-66-NH2 a promising potential absorbent material for wastewater treatment and even in other important areas of water research.

A Mesoporous Magnetic Fe3O4/BioMOF-13 with a Core/Shell Nanostructure for Targeted Delivery of Doxorubicin to Breast Cancer Cells

In the current project, magnetic Bio-MOF-13 was used as an efficient carrier for the targeted delivery and controlled release of doxorubicin (DOX) to MDA-MB-231 cells. Magnetic Bio-MOF-13 was prepared by two strategies and compared to determine the optimal state of the structure. In the first path, Bio-MOF-13 was grown in situ on the surface of Fe3O4 nanoparticles (core/shell structure), while in the second method, the two presynthesized materials were mixed together (surface composite). Core/shell structure, among prepared nanocomposites, was chosen for biological evaluation due to its favorable structural features like a high accessible surface area and pore volume. Also, it is highly advantageous for drug release due to its ability to selectively release DOX in the acidic pH of breast cancer cells, while preventing any premature release in the neutral pH of the blood. Drug release from the carrier structure is precisely controlled not only by pH but also by an external magnetic field, guaranteeing accurate drug delivery at the intended location. Confocal microscopy and flow cytometry assay clearly confirms the increase in drug concentration in the MDA-MB-231 cell line after external magnet applying. This point, along with the low toxicity of the carrier components, makes it a suitable candidate for injectable medicine. According to MTT results, the percentage of viable MDA-MB-231 cells after treatment with 10 μL of DOX@Fe3O4/Bio-MOF-13 core/shell composite in different concentrations, in the presence and absence of magnetic field is 0.87 ± 0.25 and 2.07 ± 0.15, respectively. As a result, the DOX@Fe3O4/Bio-MOF-13 core/shell composite was performed and approved for targeted drug delivery and magnetic field-assisted controlled release of DOX to the MDA-MB-231 cell line.

Mixed valence copper oxide composites derived from metal-organic frameworks for efficient visible light fuel denitrification

The construction of heterojunctions has been used to optimize photocatalyst fuel denitrification. In this work, HKUST-1(Cu) was used as a sacrificial template to synthesize a composite material CuxO (CuO/Cu2O) that retains the original MOF framework for photocatalytic fuel denitrification by calcination at different temperatures. By adjusting the temperature, the content of CuO/Cu2O can be changed to control the performance and structure of CuxO-T effectively. The results show that CuxO-300 has the best photocatalytic performance, and its denitrification rate reaches 81% after 4 hours of visible light (≥420 nm) irradiation. Through the experimental analysis of pyridine's infrared and XPS spectra, we found that calcination produces CuxO-T mixed-valence metal oxide, which can create more exposed Lewis acid sites in the HKUST-1(Cu) framework. This leads to improved pyridine adsorption capabilities. The mixed-valence metal oxide forms a type II semiconductor heterojunction, which accelerates carrier separation and promotes photocatalytic activity for pyridine denitrification.

Modulated Ultrathin NiCo-LDH Nanosheet-Decorated Zr3+-Rich Defective NH2-UiO-66 Nanostructure for Efficient Photocatalytic Hydrogen Evolution

Defect engineering through modification of their surface linkage is found to be an effective pathway to escalate the solar energy conversion efficiency of metal-organic frameworks (MOFs). Herein, defect engineering using controlled decarboxylation on the NH2-UiO-66 surface and integration of ultrathin NiCo-LDH nanosheets synergizes the hydrogen evolution reaction (HER) under a broad visible light regime. Diversified analytical methods including positron annihilation lifetime spectroscopy were employed to investigate the role of Zr3+-rich defects by analyzing the annihilation characteristics of positrons in NH2-UiO-66, which provides a deep insight into the effects of structural defects on the electronic properties. The progressively tuned photophysical properties of the NiCo-LDH@NH2-UiO-66-D-heterostructured nanocatalyst led to an impressive rate of HER (∼2458 μmol h-1 g-1), with an apparent quantum yield of ∼6.02%. The ultrathin NiCo-LDH nanosheet structure was found to be highly favored toward electrostatic self-assembly in the heterostructure for efficient charge separation. Coordination of Zr3+ on the surface of the NiCo-LDH nanosheet support through NH2-UiO-66 was confirmed by X-ray absorption spectroscopy and electron paramagnetic resonance spectroscopy techniques. Femtosecond transient absorption spectroscopy studies unveiled a photoexcited charge migration process from MOF to NiCo-LDH which favorably occurred on a picosecond time scale to boost the catalytic activity of the composite system. Furthermore, the experimental finding and HER activity are validated by density functional theory studies and evaluation of the free energy pathway which reveals the strong hydrogen binding over the surface and infers the anchoring effect of the ultrathin layered double hydroxide (LDH) in the vicinity of the Zr cluster with a strong host-guest interaction. This work provided a novel insight into efficient photocatalysis via defect engineering at the linker modulation in MOFs.

Sustainable production of Fe-doped MnO2 nanoparticles for accelerated tetracycline antibiotic detoxification

Manganese dioxide (MnO2) has been recognized as one of the natural systems' most active mineral oxidants. However, when it comes to catalytic oxidation of antibiotic applications, pure MnO2 falls short in delivering satisfactory performance. Hence, a set of Fe3+-doped porous MnO2 (0.02Fe-MnO2, 0.1Fe-MnO2, and 0.14Fe-MnO2) nanoparticles were synthesized here via a convenient and energy-efficient one-step reaction method. A series of experiments revealed that Fe-doping strategy enhances the properties of MnO2 host by suppressing the crystalline structure, increasing the amount of surface oxygen defects, and modifying the Mn3+/Mn4+ ratio. Specifically, the tetracycline (TC) removal efficiency of 0.14Fe-MnO2 reaches 92% without the need for any additional co-oxidant, representing a 20% improvement over pristine MnO2 nanoparticles. Moreover, this process shows a fast dynamic (achieving 70% of TC removal in just 5 min) and demonstrates pH-resistance, maintaining high TC removal efficiency (≥90%) over a wide pH range of 3.0-9.0. Mechanical studies reveal that the degradation of TC can be attributed to the oxidation by reactive oxygen radicals and Mn3+, with 1O2 being the primary radical involved in the reaction, accounting for 55% of TC removal. Importantly, cytotoxicity testing indicates that the biotoxicity of TC toward organisms can be effectively mitigated using 0.14Fe-MnO2 nanomaterial. This study presents a readily applicable candidate for economically and conveniently eliminating of environmental TC pollution, thereby reducing the threat posed by TC pollution to the ecosystem.

Empowering Adsorption and Photocatalytic Degradation of Ciprofloxacin on BiOI Composites: A Material-by-Design Investigation

Binary and ternary composites of BiOI with NH2-MIL-101(Fe) and a functionalized biochar were synthesized through an in situ approach, aimed at spurring the activity of the semiconductor as a photocatalyst for the removal of ciprofloxacin (CIP) from water. Experimental outcomes showed a drastic enhancement of the adsorption and the equilibrium (which increased from 39.31 mg g-1 of bare BiOI to 76.39 mg g-1 of the best ternary composite in 2 h time), while the kinetics of the process was not significantly changed. The photocatalytic performance was also significantly enhanced, and the complete removal of 10 ppm of CIP in 3 h reaction time was recorded under simulated solar light irradiation for the best catalyst of the investigated batch. Catalytic reactions supported by different materials obeyed different reaction orders, indicating the existence of different mechanisms. The use of scavengers for superoxide anion radicals, holes, and hydroxyl radicals showed that although all these species are involved in CIP photodegradation, the latter play the most crucial role, as also confirmed by carrying out the reaction at increasing pH conditions. A clear correlation between the reduction of BiOI crystallite sizes in the composites, as compared to the bare material, and the material performance as both adsorbers and photocatalyst was identified.

Rational design of MOF@COF composites with multi-site functional groups for enhanced elimination of U(VI) from aqueous solution

Both environment and human beings were menaced by the widespread application of radioactive uranium, high-performance and effective elimination of uranium from wastewater is of important meaning for development of environmental sustainability in the future. In this study, the water-stable MOF material and the highly crystalline COF were compounded by a mild hydrothermal strategy, which achieved efficient removal of U(VI) through the synergistic effect. The composites showed the characteristics of both COFs and MOFs, which will possess higher stability, larger surface area and faster adsorption efficiency that cannot be carried out by a single component. Batch experiments and characterizations (SEM, TEM, XRD, FT-IR, BET, XPS, etc.) indicated that UiO-66-NH2@LZU1 had more stable and multi-layer pore structure and rich active functional groups. The Langmuir model and the pseudo-second-order kinetics fitting was more suitable for the U(VI) elimination process. The greatest uranium adsorbing capacity of UiO-66-NH2@LZU1 (180.4 mg g-1) was observed to exceed the UiO-66-NH2 (108.8 mg g-1) and COF-LZU1 (65.8 mg g-1), which reached the excellent hybrid effects. Furthermore, FT-IR and XPS analyses confirmed that the most nitrogen-containing group from COF-LZU1 and oxygen-containing group of UiO-66-NH2 could be combined with U(VI). In addition, electrostatic interaction was also a mechanism during the removal process. This work displayed that UiO-66-NH2@LZU1 was a prospective hybrid material for radioactive waste remediation. The compound method and application mentioned in this work had provided a theoretical basis for designing and developing multi-functional composite adsorbents, which contributed to the development of new materials for radioactive wastewater treatment technologies.

Covalently anchoring silver nanoclusters Ag44 on modified UiO-66-NH2 with Bi2S3 nanorods and MoS2 nanoparticles for exceptional solar wastewater treatment activity

For the first time, covalently anchoring size selected silver nanoclusters [Ag44(MNBA)30] on the Bi2S3@UiO-66-NH2 and MoS2@UiO-66-NH2 heterojunctions were constructed as novel photocatalysts for photodegradation of methylene blue (MB) dye. The anchoring of Ag44 on MoS2@UiO-66-NH2 and Bi2S3@UiO-66-NH2 heterojunctions extended the light absorption of UiO-66-NH2 to the visible region and improved the transfer and separation of photogenerated charge carriers through the heterojunctions with a unique band gap structure. The UV-Vis-NIR diffuse reflectance spectroscopic analysis confirmed that the optical absorption properties of the UiO-66-NH2 were shifted from the UV region at 379 nm to the visible region at ~ 705 nm after its doping with Bi2S3 nanorods and Ag44 nanoclusters (Bi2S3@UiO-66-NH-S-Ag44). The prepared Bi2S3@UiO-66-NH-S-Ag44 and MoS2@UiO-66-NH-S-Ag44 photocatalysts exhibited exceptional photocatalytic activity for visible light degradation of MB dye. The photocatalysts exhibited complete decolorization of the MB solution (50 ppm) within 90 and 120 min stirring under visible light irradiation, respectively. The supper photocatalytic performance and recycling efficiency of the prepared photocatalysts attributed to the covalent anchoring of the ultra-small silver clusters (Ag44) on the heterojunctions surface. The X-ray photoelectron spectroscopic analysis confirmed the charge of the silver clusters is zero. The disappearance of the N-H bending vibration peak of primary amines in the FTIR analysis of Bi2S3@UiO-66-NH-S-Ag44 confirmed the covalent anchoring of the protected silver nanoclusters on the UiO-66-NH2 surface via the condensation reaction. The Bi2S3@UiO-66-NH-S-Ag44 catalyst exhibited excellent recyclability efficiency more than five cycles without significant loss in activity, indicating their good potential for industrial applications. The texture properties, crystallinity, phase composition, particle size, and structural morphology of the prepared photocatalysts were investigated using adsorption-desorption N2 isotherms, X-ray diffraction (XRD), HR-TEM, and FE-SEM, respectively.

Recent Advances in Metal-Organic Framework (MOF)-Based Photocatalysts: Design Strategies and Applications in Heavy Metal Control

The heavy metal contamination of water systems has become a major environmental concern worldwide. Photocatalysis using metal-organic frameworks (MOFs) has emerged as a promising approach for heavy metal remediation, owing to the ability of MOFs to fully degrade contaminants through redox reactions that are driven by photogenerated charge carriers. This review provides a comprehensive analysis of recent developments in MOF-based photocatalysts for removing and decontaminating heavy metals from water. The tunable nature of MOFs allows the rational design of composition and features to enhance light harvesting, charge separation, pollutant absorptivity, and photocatalytic activities. Key strategies employed include metal coordination tuning, organic ligand functionalization, heteroatom doping, plasmonic nanoparticle incorporation, defect engineering, and morphology control. The mechanisms involved in the interactions between MOF photocatalysts and heavy metal contaminants are discussed, including light absorption, charge carrier separation, metal ion adsorption, and photocatalytic redox reactions. The review highlights diverse applications of MOF photocatalysts in treating heavy metals such as lead, mercury, chromium, cadmium, silver, arsenic, nickel, etc. in water remediation. Kinetic modeling provides vital insights into the complex interplay between coupled processes such as adsorption and photocatalytic degradation that influence treatment efficiency. Life cycle assessment (LCA) is also crucial for evaluating the sustainability of MOF-based technologies. By elucidating the latest advances, current challenges, and future opportunities, this review provides insights into the potential of MOF-based photocatalysts as a sustainable technology for addressing the critical issue of heavy metal pollution in water systems. Ongoing efforts are needed to address the issues of stability, recyclability, scalable synthesis, and practical reactor engineering.

Self-assembled BiFeO3@MIL-101 nanocomposite for antimicrobial applications under natural sunlight

In this paper, we report on the synthesis of a new hybrid photocatalytic material activated by natural sunlight irradiation. The material consists of multiferroic nanoparticles of bismuth ferrite (BFO) modified through the growth of the Fe-based MIL-101 framework. Material characterization, conducted using various techniques (X-ray diffraction, transmission electron microscopy, FTIR, and X-ray photoelectron spectroscopies), confirmed the growth of the MIL-101 metal-organic framework on the BFO surface. The obtained system possesses the intrinsic photo-degradative properties of BFO nanoparticles significantly enhanced by the presence of MIL-101. The photocatalytic activity of this material was tested in antibacterial experiments conducted under natural sunlight exposure within the nanocomposite concentration range of 100-0.20 µg/ml. The MIL-modified BFO showed a significant decrease in both Minimum Inhibiting Concentration and Minimum Bactericide Concentration values compared to bare nanoparticles. This confirms the photo-activating effect of the MIL-101 modification. In particular, they show an increased antimicrobial activity against the tested Gram-positive species and the ability to begin to inhibit the growth of the four Escherichia coli strains, although at the maximum concentration tested. These results suggest that the new nanocomposite BiFeO3@MOF has been successfully developed and has proven to be an effective antibacterial agent against a wide range of microorganisms and a potential candidate in disinfection processes.

Nanoscale designing of metal organic framework moieties as efficient tools for environmental decontamination

Environmental pollutants, being a major and detrimental component of the ecological imbalance, need to be controlled. Serious health issues can get intensified due to contaminants present in the air, water, and soil. Accurate and rapid monitoring of environmental pollutants is imperative for the detoxification of the environment and hence living beings. Metal-organic frameworks (MOFs) are a class of porous and highly diverse adsorbent materials with tunable surface area and diverse functionality. Similarly, the conversion of MOFs into nanoscale regime leads to the formation of nanometal-organic frameworks (NMOFs) with increased selectivity, sensitivity, detection ability, and portability. The present review majorly focuses on a variety of synthetic methods including the ex situ and in situ synthesis of MOF nanocomposites and direct synthesis of NMOFs. Furthermore, a variety of applications such as nanoabsorbent, nanocatalysts, and nanosensors for different dyes, antibiotics, toxic ions, gases, pesticides, etc., are described along with illustrations. An initiative is depicted hereby using nanostructures of MOFs to decontaminate hazardous environmental toxicants.

Recent strategies for constructing hierarchical multicomponent nanoparticles/metal-organic framework hybrids and their applications

Hybrid nanoparticles with unique tailored morphologies and compositions can be utilized for numerous applications owing to their combination of inherent properties as well as the structural and supportive functions of each component. Controlled encapsulation of nanoparticles within nanospaces (NPNSs) of metal-organic frameworks (MOFs) (denoted as NPNS@MOF) can generate a large number of hybrid nanomaterials, facilitating superior activity in targeted applications. In this review, recent strategies for the fabrication of NPNS@MOFs with a hierarchical architecture, tailorability, unique intrinsic properties, and superior catalytic performance are summarized. In addition, the latest and most important examples in this sector are emphasized since they are more conducive to the practical applicability of NPNS@MOF nanohybrids.

Preparation of TiO2/Fe-MOF n‒n heterojunction photocatalysts for visible-light degradation of tetracycline hydrochloride

Visible-light-assisted photocatalysis has been recognized as an effective solution to the degradation of various pollutants including antibiotics, pesticides, herbicides, microplastics, and organic dyes. Herein, an n-n heterojunction TiO₂/Fe-MOF photocatalyst is reported, designed via hydrothermal synthesis route. TiO₂/Fe-MOF photocatalyst was characterized by XPS, BET, EIS, EDS, DRS, PL, FTIR, XRD, TEM, SEM and HRTEM techniques. Inspired by XRD, FTIR, XPS, EDS, TEM, SEM, and HRTEM analyses, the successful synthesis of n-n heterojunction TiO₂/Fe-MOF photocatalysts was proved. The migration efficiency of the light-induced electron-hole pairs was confirmed by the PL and EIS tests. TiO₂/Fe-MOF exhibited a significant performance for tetracycline hydrochloride (TC) removal under visible light irradiation. TC removal efficiency for TiO₂/Fe-MOF (15%) nanocomposite reached 97% within 240 min, ca. 11 times higher than pure TiO₂. The photocatalytic enhancement of TiO₂/Fe-MOF could be attributed to the broadening the light response range, forming an n-n junction between Fe-MOF and TiO₂ components, suppressing charge recombination. Based on recycling experiments, TiO₂/Fe-MOF had a good potential to be used in consecutive TC degradation tests.

MgIn2S4/UiO-66-NH2 MOF-Based Heterostructure: Visible-Light-Responsive Z-Scheme-Mediated Synergistically Enhanced Photocatalytic Performance toward Hydrogen and Oxygen Evolution

Hydrogen and oxygen evolution via photocatalytic water splitting remains the quintessential alternative to fossil fuels. Photocatalysts must be sufficiently robust, competent, and productive toward harnessing sunlight in order to utilize the solar spectrum for maximal photocatalytic output. Herein, we have fabricated the MgIn₂S₄/UiO-66-NH₂ composite via a facile solvothermal route and have determined its efficacy toward light-induced H₂ and O₂ generation reactions through water splitting with the aid of different sacrificial agents. Initially, the formation of pristine and composite materials was ascertained by PXRD, FTIR, etc. Moreover, with the aid of sophisticated morphological characterization techniques (FESEM and HRTEM), the intricate interaction between MgIn₂S₄ and UiO-66-NH₂ was revealed. Additionally, the XPS studies suggested the effective interaction between the individual components with binding energy shifting suggesting the transfer of electrons from Zr-MOF to MgIn₂S₄. The PL and electrochemical aspects supported the effective photogenerated charge segregation in the prepared composite leading to superior photocatalytic outputs. Amidst the prepared composites of (3, 5, and 7 wt %) MgIn₂S₄/UiO-66-NH₂, the 5 wt % or UM-2 composite displays optimal H₂ and O₂ evolution performances of 493.8 and 258.6 μmol h^-1 (4-fold greater than for pristine MgIn₂S₄ and UiO-66-NH₂), respectively. The nanocomposite's enhanced performance is indeed a consequence of the coadjuvant interaction among pristine UiO-66-NH₂ and MgIn₂S₄ components that transpires via the Z-scheme-mediated charge transfer by enabling facile exciton segregation and channelization. Moreover, the composite inherited the remarkable framework stability of parent Zr-MOF, and the MgIn₂S₄ insertion had a negligible impact on the framework integrity. This work will offer a valuable model for developing robust Zr-MOF-based nanocomposite photocatalysts and evaluating their superior performance toward photocatalytic water redox reactions.

Integrating Ultrasmall Pd NPs into Core-Shell Imidazolate Frameworks for Photocatalytic Hydrogen and MeOH Production

The construction of photoactive units in the proximity of a stable framework support is one of the promising strategies for uplifting photocatalysis. In this work, the ultrasmall Pd NPs implanted onto core-shell (CS) metal organic frameworks (MOFs), i.e., CS@Pd nanoarchitectures with tailored electronic and structural properties are reported. The all-in-one heterogeneous catalyst CS@Pd3 improves the surface functionalities and exhibits an outstanding hydrogen evolution reaction (HER) activity rate of 12.7 mmol g^-1 h^-1, which is 10-folds higher than the pristine frameworks with an apparent quantum efficiency (AQE) of 9.02%. The bifunctional CS@Pd shows intriguing results when subjected to photocatalytic CO₂ reduction with an impressive rate of 71 μmol g^-1 h^-1 of MeOH under visible-light irradiation at ambient conditions. Spectroscopic data reveal efficient charge migrations and an extended lifetime of 2.4 ns, favoring efficient photocatalysis. The microscopic study affirms the formation of well-ordered CS morphology with precise decoration of Pd NPs over the CS networks. The significance of active Pd and Co sites is addressed by congruent charge-transfer kinetics and computational density functional theory calculations of CS@Pd, which validate the experimental findings with their synergistic involvement in improved photocatalytic activity. This present work provides a facile and competent avenue for the systematic construction of MOF-based CS heterostructures with active Pd NPs.

Hydrolytically stable mixed ditopic linker based zirconium metal organic framework as a robust photocatalyst towards Tetracycline Hydrochloride degradation and hydrogen evolution

In the existing eco-crisis, designing and engineering an efficient as well as water stable photocatalyst for energy conversion and pollutant abatement remains crucial. In this regard, a mixed linker type zirconium metal organic framework (Zr-MOF) with terepthalic acid based ditopic linkers were utilized to design a single component photocatalyst through single step solvothermal method to utilize photons from visible light illumination towards hydrogen energy (H2) production and Tetracycline Hydrochloride (TCH) degradation. The one pot synthesized mixed linker based Zr-MOF displays visible light absorption through band gap tuning, superior exciton segregation and oxygen vacancy that cumulatively supports the enhancement in the photocatalytic output with respect to their pristine counterparts. Additionally, the X-ray photoelectron spectroscopy, optical and electrochemical studies strongly reinforces the above claims. The prepared mixed linker Zr-MOF showed superior photocatalytic H2 evolution performance of 247.88 µmol h-1 (apparent conversion efficiency; ACE = 1.9%) that is twice than its pristine Zr-MOFs. Moreover, in TCH degradation, the mixed linker MOF displays an enhanced efficacy of 91.8 % and adopts pseudo-first order type kinetics with a rate constant value of 0.032. Typically, the active species participating for the TCH photo-degradation follows the order of hydroxyl (OH.) < superoxide (O2.-) radicals. Consequently, the mixed linker Zr-MOF could be effectively used as a robust photocatalyst exhibiting boosted TCH degradation and H2 production.

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.

Metal organic framework-based Janus nanomaterials: rational design, strategic fabrication and emerging applications

Janus nanoparticles (JNPs) with dual segments comprising chemically distinct compositions have garnered the attention of researchers in the past few years. The combination of different materials with diversified morphology, topology, and distinct physico-chemical characteristics into the single Janus nanocrystal has yielded multifarious capabilities for a myriad of emerging applications involving catalysis, gas separation, electro-catalysis, adsorption and energy storage. However, the traditional Janus entities significantly lack the need for populous active sites and high surface area. To overcome the textural hurdles and improve the functionalities of JNPs, porous MOFs were eventually introduced into Janus particles. MOFs are well endowed with varied pore apertures, structures, large surface areas and tailored characteristics, making them potentially invaluable for Janus fabrication. Depending upon the usage, MOFs can be explored to design Metal@MOF, polymetalic@MOF, MOF@MOF and MOF-derived JNPs. In this regard, we have represented a holistic summarization of the design, synthesis and emerging applications of a rising class of multi-functionalized MOF-based Janus nanomaterials. Moreover, this article will significantly aid researchers with a vision of creating dual-composition porous nanomaterials as the MOF-based Janus nanoparticles is at infancy.

Strategies for the application of metal-organic frameworks in catalytic reactions

Efficient catalysts play crucial roles in various organic reactions and polymerization. Metal–organic frameworks (MOFs) have the merits of ultrahigh porosity, large surface area, dispersed polymetallic sites and modifiable linkers, which make them promising candidates for catalyzation. This review primarily summarizes the recent research progress on diverse strategies for tailoring MOFs that are endowed with excellent catalytic behavior. These strategies include utilizing MOFs as nanosized reaction channels, metal nodes decorated as catalytic active sites and the modification of ligands or linkers. All these make them highly attractive to various applications, especially in catalyzing organic reactions or polymerizations and they have proven to be effective catalysts for a wide variety of reactions. MOFs are still an evolving field with tremendous prospects; therefore, through the research and development of more modification and regulation strategies, MOFs will realize their wider practical application in the future.

Metal–organic frameworks (MOFs) are promising candidates for catalyzation. This review primarily summarized the recent research progress in diverse strategies for tailoring MOFs which are endowed with more excellent catalytic behavior.

Mixed-Valence Bimetallic Ce/Zr MOF-Based Nanoarchitecture: A Visible-Light-Active Photocatalyst for Ciprofloxacin Degradation and Hydrogen Evolution

A mixed-valency bimetallic Ce/Zr MOF with Ce³⁺/Ce⁴⁺ ions incorporated and an oxygen vacancy-rich single-component photocatalyst have been designed through the one-step solvothermal route to harness photons from the visible-light spectrum for green energy (H₂) generation and ciprofloxacin (CIP) degradation. The one-pot-engineered bimetallic Ce/Zr MOF shows visible-light-active characteristics accompanied by a narrower band gap, along with enhanced exciton separation and superior ligand-to-metal charge transfer (LMCT), due to the presence of an interconvertible Ce³⁺/Ce⁴⁺ ions pair in comparison to its pristine MOF counterpart. The Ce ion insertion led to increase in electron density around the Zr⁴⁺ ion, along with generation of some oxygen vacancies (OV), which cumulatively led to the rise in the photo-reaction output. The synthesized UNH (Ce/Zr 1:1) MOF displayed a boosted photocatalytic H₂ production rate of 468.30 μmol h^-1 (ACE = 3.51%), which is around fourfolds higher than that of pristine MOFs. Moreover, for CIP photodegradation, the UNH (Ce/Zr 1:1) shows an enhanced efficiency of 90.8% and follows pseudo-first-order kinetics with a rate constant of 0.0363. Typically, the active species involved in the photo-redox reaction of the CIP photodegradation follows the order hydroxyl radical (OH^•) < superoxide radical (O₂^•-), as confirmed by the TA and NBT tests. Consequently, the bimetallic Ce/Zr MOF can be readily employed as a robust photocatalyst with enhanced tendencies towards CIP degradation and H₂ evolution.

Challenges and prospects in the selective photoreduction of CO2 to C1 and C2 products with nanostructured materials: a review

Solar fuel generation through CO₂ hydrogenation is the ultimate strategy to produce sustainable energy sources and alleviate global warming. The photocatalytic CO₂ conversion process resembles natural photosynthesis, which regulates the ecological systems of the earth. Currently, most of the work in this field has been focused on boosting efficiency rather than controlling the distribution of products. The structural architecture of the semiconductor photocatalyst, CO₂ photoreduction process, product analysis, and elucidating the CO₂ photoreduction mechanism are the key features of the photoreduction of CO₂ to generate C1 and C2 based hydrocarbon fuels. The selectivity of C1 and C2 products during the photocatalytic CO₂ reduction have been ameliorated by suitable photocatalyst design, co-catalyst, defect states, and the impacts of the surface polarisation state, etc. Monitoring product selectivity allows the establishment of an appropriate strategy to generate a more reduced state of a hydrocarbon, such as CH₄ or higher carbon (C2) products. This article concentrates on studies that demonstrate the production of C1 and C2 products during CO₂ photoreduction using H₂O or H₂ as an electron and proton source. Finally, it highlights unresolved difficulties in achieving high selectivity and photoconversion efficiency of CO₂ in C1 and C2 products over various nanostructured materials.

Cu/CuxO@C nanocomposites as efficient electrodes for high-performance supercapacitor devices

A novel method, reduction followed by oxidation procedure, has been developed to fabricate the efficient electrodes derivated from metal-organic frameworks (MOFs), which were synthesized using terephthalic acid (TP) or 1,3,5-benzenetricarboxylic...

Photocatalytic Activity of Supported Metal Nanoparticles and Single Atoms

Photocatalysis has been known as one of the promising technologies due to its eco-friendly nature. However, the potential application of many photocatalysts is limited owing to their large bandgaps and inefficient use of the solar spectrum. One strategy to overcome this problem is to combine the advantages of heteroatom-containing supports with active metal centers to accurately adjust the structural parameters. Metal nanoparticles (MNPs) and single atom catalysts (SACs) are excellent candidates due to their distinctive coordination environment which enhances photocatalytic activity. Metal-organic frameworks (MOFs), covalent organic frameworks (COFs) and carbon nitride (g-C₃ N₄ ) have shown great potential as catalyst support for SACs and MNPs. The numerous combinations of organic linkers with various heteroatoms and metal ions provide unique structural characteristics to achieve advanced materials. This review describes the recent advancement of the modified MOFs, COFs and g-C₃ N₄ with SACs and NPs for enhanced photocatalytic applications with emphasis on environmental remediation.

Porous Organic Polymers for Catalytic Conversion of Carbon Dioxide

To overcome the challenges of global warming and environmental pollution, it is necessary to reduce the concentration of carbon dioxide (CO₂ ) in the atmosphere, which is mainly accumulated in the air through the burning of fossil fuels. Therefore, the development of environmentally friendly strategies to capture carbon dioxide and convert it into value-added products offers a promising way forward for reducing carbon dioxide concentration in the atmosphere. In this context, POPs (porous organic polymers) have shown great potential as CO₂ selective adsorbents due to their high specific surface area, chemical stability, nanoscale porosity and structural diversity, as well as POPs based heterogeneous catalysts for CO₂ conversion. This review provides a concise account of preparation methods of various POPs, challenges and current development trends of POPs in photocatalytic CO₂ reduction, electrocatalytic CO₂ reduction and chemical CO₂ conversion.

Hydrolytically stable citrate capped Fe3O4@UiO-66-NH2 MOF: A hetero-structure composite with enhanced activity towards Cr (VI) adsorption and photocatalytic H2 evolution

Design and facile fabrication of a magnetically separable hetero-structure photocatalyst as well as an adsorbent having dual green benefits towards energy conversion and pollutant remediation are quite indispensable in the current scenario. In this regard, a composite of citrate capped Fe₃O₄ and UiO-66-NH₂ has been designed to remediate Cr (VI) by adsorption and harvest photons from visible light for clean energy (H₂) conversion. The material was prepared by the union of citrate capped Fe₃O₄ (CCM) and versatile aqueous stable Zr-based MOF (UiO-66-NH₂) through in-situ solvothermal method. The composite of CCM with MOF (MU-2) was studied through sophisticated analysis techniques; PXRD, FT-IR, BET, UV-Visible DRS, PL, TG, HRTEM and XPS etc. to reveal the inherent characteristics of the material. BET surface analysis revealed high specific surface area (572.13 m² g^-1) of MU-2 in comparison to its pristine MOF. Furthermore, the dual function composite MU-2's VSM studies showed that its magnetic saturation is 3.07 emu g^-1 that is suitable for magnetic separation after desired reaction from aqueous media. The Cr (VI) sorption studies revealed that the composite adsorbent (MU-2) showed maximum monolayer adsorption capacity (Q_m) of 743 mg g^-1 which followed pseudo second order kinetics. Moreover, the sorption thermodynamics revealed that the process was spontaneous and endothermic in nature. In addition to it, the synthesized composite material displayed enhanced activity towards photocatalytic H₂ evolution with a maximum evolution rate of 417 µmole h^-1 with an apparent conversion efficiency (ACE) of 3.12 %. Typically, MU-2 displays high adsorptions of Cr (VI) as well as some extent of Cr (VI) reduction owning to its populous active sites and free carboxylate groups respectively. Moreover, the synergistic effect of CCM and UNH in the composite resulted in Z scheme mediated charge transfer mechanism that showed enhanced H₂ photo-evolution rates. Hence, MU-2 can be readily utilized as magnetically retrievable dual function composite for Cr (VI) adsorption and photocatalytic H₂ evolution.