Coupling MOF-based photocatalysis with Pd catalysis over Pd@MIL-100(Fe) for efficient N-alkylation of amines with alcohols under visible light

A sustainable strategic approach for N-alkylation of amines with activation of alcohols triggered via a hydrogen auto-transfer reaction using a Pd(II) complex: evidence for metal-ligand cooperativity

This work describes a new well-defined, air-stable, phosphine free palladium(II) [Pd(L)Cl] (1) catalyst. This catalyst was utilized for N-alkylation of amines and indole synthesis where H2O was found to be the by-product. A broad range of aromatic amines were alkylated using this homogeneous catalyst with a catalyst loading of 0.1 mol%. Greener aromatic and aliphatic primary alcohols were utilized and a hydrogen auto-transfer strategy via a metal-ligand cooperative approach was investigated. The precursor of the antihistamine-containing drug molecule tripelennamine was synthesized on a gram scale for large-scale applicability of the current synthetic methodology. A number of control experiments were performed to investigate the possible reaction pathway and the outcomes of these experiments indicated the azo-chromophore as a hydrogen reservoir during the catalytic cycle.

Efficient one-pot syntheses of secondary amines from nitro aromatics and benzyl alcohols over Pd/NiTi-LDH under visible light

Solar energy-induced cascade/tandem reactions in one-pot are sustainable and green. Herein, the Pd/NiTi-LDH nanocomposite, with Pd nanoparticles (NPs) (∼3-6 nm) deposited on NiTi-LDH nanosheets, was obtained and was applied in the reaction between nitro aromatics and alcohols to synthesize secondary amines under visible light. The superior performance observed over the as-obtained Pd/NiTi-LDH nanocomposite for this reaction can be attributed to a successful merging of Pd-based hydrogenation and LDH-based photocatalysis, in which consecutive light-induced hydrogenation of nitro compounds to amines, dehydrogenation of alcohols to aldehydes, condensation between the in situ formed aldehydes and amines to imines and the hydrogenation of final imines to generate the desired secondary amines were realized in one pot over Pd/NiTi-LDH under visible light. This work shows an effective and green strategy in the synthesis of secondary amines. This study also demonstrates the high potential of using metal/LDH nanocomposites for light-initiated organic syntheses.

MOFs as Versatile Catalysts: Synthesis Strategies and Applications in Value-Added Compound Production

Catalysts played a crucial role in advancing modern human civilization, from ancient times to the industrial revolution. Due to high cost and limited availability of traditional catalysts, there is a need to develop cost-effective, high-activity, and nonprecious metal-based electrocatalysts. Metal-organic frameworks (MOFs) have emerged as an ideal candidate for heterogeneous catalysis due to their physicochemical properties, hybrid inorganic/organic structures, uncoordinated metal sites, and accessible organic sections. MOFs are high nanoporous crystalline materials that can be used as catalysts to facilitate polymerization reactions. Their chemical and structural diversity make them effective for various reactions compared to traditional catalysts. MOFs have been applied in gas storage and separation, ion-exchange, drug delivery, luminescence, sensing, nanofilters, water purification, and catalysis. The review focuses on MOF-enabled heterogeneous catalysis for value-added compound production, including alcohol oxidation, olefin oligomerization, and polymerization reactions. MOFs offer tunable porosity, high spatial density, and single-crystal XRD control over catalyst properties. In this review, MOFs were focused on reactions of CO2 fixation, CO2 reduction, and photoelectrochemical water splitting. Overall, MOFs have great potential as versatile catalysts for diverse applications in the future.

Photocatalytic Degradation of Dyes Using Titania Nanoparticles Supported in Metal-Organic Materials Based on Iron

Composite materials based on titania nanoparticles (TiO2 NPs) and three metal-organic frameworks (MOFs) called MIL-53 (Fe) ((Fe (III) (OH) (1,4-BDC)), MILs (Materials Institute Lavoisier)), MIL-100 (Fe) (Fe3O(H2O)2OH(BTC)2), and Fe-BTC (iron-benzenetricarboxylate) with different percentages of TiO2 NPs (0.5, 1, and 2.5% wt.) were synthesized using the solvothermal method and used as photocatalytic materials in the degradation of two dyes (Orange II and Reactive Black 5 (RB5)). The pristine and composite materials were characterized with X-ray diffraction, Raman, UV–Vis and Fourier transform infrared spectroscopy and scanning electron microscopy techniques. The 2.5TiO2/MIL-100 composite material showed the best results for the degradation of both dyes (Reactive Black 5 and Orange II dye, 99% and 99.5% degradation in 105 and 150 min, respectively). The incorporation of TiO2 NPs into MOFs can decrease the recombination of the change carrier in the MOF, increasing the photocatalytic activity of a pristine MOF. Results therefore indicated that the synthesized MOF nanocomposites have good potential for wastewater treatment.

Pt nanoclusters embedded Fe-based metal-organic framework as a dual-functional electrocatalyst for hydrogen evolution and alcohols oxidation

Design and construction of high-efficiency and durable dual-functional electrocatalyst for clean energy electrocatalytic reaction is urgently desirable for mitigating the energy shortage and environmental deterioration issues. Herein, we prepared Pt nanoclusters with exposed (111) face plane embedded Fe-based metal-organic frameworks (Fe-MOF, MIL-100(Fe)) catalyst for electrocatalytic hydrogen evolution reaction (HER) and ethylene glycol oxidation reaction (EGOR). It is noted that the available oxygen sites on the surface of MIL-100(Fe) would form Pt-O interaction with Pt nanoclusters to acquire strong interfacial interaction, which endows Pt/MIL-100(Fe) electrocatalyst effective electron transfer, increasing catalytic active sites, accelerating proton-electron coupling, and improving conductivity. Benefitting from the desirable metal-supports interaction and derive merits for catalysis, the high electrocatalytic activity and durability for HER and EGOR were achieved as expected. Impressively, superior HER performance with higher current density, lower overpotential (46/29 mV in acidic/alkaline electrolyte) and smaller Tafel slope (19.7/37.8 mV dec^-1 in acidic/alkaline electrolyte) were acquired compared to commercial Pt/C. Moreover, Pt/MIL-100(Fe) electrode exhibits a rather high mass activity of 11826 mA mg^-1_Pt and long-term stability for EGOR. The present investigation demonstrates the promise of active metal/MOF combination for the interfacial strategy and rational design of dual-functional electrocatalyst, which has potential applications for future electrocatalysis field.

Synthesis, modifications and applications of MILs Metal-organic frameworks for environmental remediation: The cutting-edge review

Ever-increasing anthropogenic activities are radically deteriorating the environment by causing severe pollution. Thus, curtailing the environmental pollution and promotion of sustainable development, are the hot issues confronted by scientists in this modern era. Metal-organic frameworks (MOFs) have been highly recognized as emerging promising materials for environmental remediation due to their versatile structure and extraordinary properties. Among them, MILs (MIL = Matérial Institute of Lavoisier) are the series of MOFs mostly known for their incredible stability, unique tailorable pore structures, and astounding versatile environmental applications. Their exclusive physiochemical properties and multifunctionality make them proficient for a wide range of pollutants removal in the exposure of versatile harsh environments, compared to other MOFs. This piece of research summarizes the state-of-the-art of development of MILs on the broad spectrum, highlighting their specificities, such as synthesis techniques, modifications and applications for environmental remediation. However, MILs wonderful properties and extraordinary applications in multiple fields, their deployment on practical and commercial-scale pollutants remediation is hindered by insufficient scientific research on underlying mechanisms and relationships. Henceforth, this review not only signifies the emerging importance of MILs for environmental applications but also indicates the urgency to maximize the scientific research for exploitation of MOFs on a practical level and promotion of green technologies for environmental remediation.

A Theoretical Study on the Borane-Catalyzed Reductive Amination of Aniline and Benzaldehyde with Dihydrogen: The Origins of Chemoselectivity

Density functional theory calculations are used in this study to investigate the product selectivity and mechanism of borane-catalyzed reductive aldehyde amination by a H₂ reducing agent. Knowing that different boranes yield different products, two typical boranes, (B(2,6-Cl₂C₆H₃)(p-HC₆F₄)₂ and B(C₆F₅)₃), are studied. Of the seven possible pathways of B(2,6-Cl₂C₆H₃)(p-HC₆F₄)₂-catalyzed aldehyde amination analyzed herein, four are favorable. Three of the four favorable pathways involve imine intermediates, and the fourth is a Lewis acid-base synergistic pathway that involves amine-alcohol condensation. As for the B(C₆F₅)₃ catalyst, it forms a highly stable Lewis adduct with aniline, which impedes the hydrogenation of imine. Therefore, the product of B(C₆F₅)₃-catalyzed reductive amination of benzaldehyde and aniline is an imine. The linear relationship between the charge on the boron atom in the Lewis acid and the relative energies of the Lewis adduct and H₂ splitting transition state indicates that this parameter determines product selectivity. Indeed, when the natural charge on boron is larger than 1, an amine is produced, whereas when the charge is less than 1, an imine is produced. Hence, the selectivity of products can be controlled by adjusting the natural charge of the boron atom in the Lewis acid catalyst.

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...

Solvent/metal-free benzimidazolium-based carboxyl-functionalized porphyrin photocatalysts for the room-temperature alkylation of amines under the irradiation of visible light

The improvement of novel sustainable catalytic methods for green chemical production is an emergent area in chemical science.

Palladium Nanoparticles Supported on Cellulosic Paper as Multifunctional Catalyst for Coupling and Hydrogenation Reactions

Hallmark of a successful catalyst is its high efficiency, economic aspects, operational simplicity, extensive reusability, higher environment friendliness, and potential use in multiple industrial applications. Herein, a facile protocol involving a catalyst with Pd nanoparticles supported on cellulose paper (also known as a "dip-catalyst") for the hydrogenation of a series of quinolines, nitroarene, and C-C bond formation reactions in most benign solvents such as water is described. The mere insertion/removal of the "dip-catalyst" strip enables instantaneous start/stop of the reaction, which enhances its reusability and ease of separation of products. Cellulose paper (CP) strips decorated with Pd nanoparticles (Pd/CP) are prepared by the reduction of K₂ PdCl₄ soaked strips using formic acid as reductant. The resulting spherical shaped Pd particles, confirmed by scanning electron microscopy, form stable catalysis centers on the support. XRD signature confirms the crystallinity of the Pd nanoparticles and the TEM images display 15-20 nm size particles uniformly decorating CP. X-ray photoelectron spectroscopy indicates the formation of metallic Pd. The catalyst is tested for the C-C bond formation reactions. Pd/CP catalyzed Suzuki-Miyaura coupling reaction demonstrate >99% conversion with optimum selectivity. On the other hand, Mizoroki-Heck reaction produced 87% conversion with the reaction of 4-methoxycarbonyl phenylboronic acid and iodobenzene in ethanol:water (1 : 1 v/v) using KOH as base. The developed Pd/CP construct produces >99% of the pyridine-ring hydrogenated product on quinoline hydrogenation using tetrahydroxydiboron (THDB) as the hydrogen source. Diverse and highly reducible functional groups were also evaluated for transfer hydrogenation, which demonstrates a high efficiency in terms of both reactivity and selectivity. The used catalysts are recyclable for the multiple cycles.

Post-synthetic modifications (PSM) on metal-organic frameworks (MOFs) for visible-light-initiated photocatalysis

The utilization of green and sustainable solar energy via photocatalysis is regarded as a promising strategy to tackle the ever-increasing energy shortage and environmental deterioration. In addition to traditional semiconductor-based photocatalysts, metal-organic frameworks (MOFs), a class of crystalline micro-mesoporous hybrid materials constructed from metal or metal nodes interconnected with multi-dentate organic linkers, are emerging as a new type of photocatalytic material. Post-synthetic modifications (PSM) on MOFs, in which chemical transformations or exchanges are made on pre-synthesized MOF materials, are found to be a powerful strategy for fabricating photoactive MOFs based on already existing MOFs. In this frontier article, different PSM strategies for the development of photoactive MOFs, including coordination on unsaturated metal sites, metalation on open coordinated sites, covalent modifications on ligands, ligand exchange, metal exchange and cavity encapsulation, have been summarized. Our views on the challenges and the direction in developing photocatalytic MOFs by PSM are also addressed. We hope that this frontier article can provide some guidance for rational designing of highly efficient MOF-based photocatalysts via PSM strategies and to stimulate more research interest to be devoted to this promising yet largely unexplored field.

Application of sand particles modified with NH2-MIL-101(Fe) as an efficient visible-light photocatalyst for Cr(VI) reduction

This study presented chemical immobilization of an iron(III)-based metal-organic framework [NH₂-MIL-101(Fe)] on the surface of sand particles and its application for Cr(VI) photocatalytic reduction using visible light. The surface of sand particles was functionalized with (3-chloropropyl)trimethoxy silane to provide the active sites for bond formation with MOF particles. Using a heat treatment step, MOF particles were bonded on the surface of sand particles, thereby providing a photocatalyst more applicable in real environments. The presence of amino-functional groups in MOF was influential in bond formation. Furthermore, they are effective in the activation of the photocatalyst under visible-light irradiation. The photocatalyst properties were investigated by FESEM, FTIR, XPS, EDS, and DRS analysis. The impact of various parameters, such as light power, irradiation and contact time, TDS impact, and pH, was examined. The composite produced by immobilization of NH₂-101(Fe) on the surface of sand-Cl showed the high Cr(VI) removal efficiency (80% at 20 mg L^-1) as a result of the strong chemical bond formation through the suitable functional groups incorporated in materials. Under the optimum conditions, the reduction rate reached more than 99% using irradiation by 1000 W visible light for 30 min.

Biorenewable carbon-supported Ru catalyst for N-alkylation of amines with alcohols and selective hydrogenation of nitroarenes

A renewable carbon-supported Ru catalyst (Ru/PNC-700) facilely prepared via simple impregnation followed by the pyrolysis process for N-alkylation of anilines with benzyl alcohol and chemoselective hydrogenation of nitroarenes.

Advances in metal-organic framework coatings: versatile synthesis and broad applications

Metal-organic frameworks (MOFs) as a new kind of porous crystalline materials have attracted much interest in many applications due to their high porosity, diverse structures, and controllable chemical structures. However, the specific geometrical morphologies, limited functions and unsatisfactory performances of pure MOFs hinder their further applications. In recent years, an efficient approach to synthesize new composites to overcome the above issues has been achieved, by integrating MOF coatings with other functional materials, which have synergistic advantages in many potential applications, including batteries, supercapacitors, catalysis, gas storage and separation, sensors, drug delivery/cytoprotection and so on. Nevertheless, the systemic synthesis strategies and the relationships between their structures and application performances have not been reviewed comprehensively yet. This review emphasizes the recent advances in versatile synthesis strategies and broad applications of MOF coatings. A comprehensive discussion of the fundamental chemistry, classifications and functions of MOF coatings is provided first. Next, by modulating the different states (e.g. solid, liquid, and gas) of metal ion sources and organic ligands, the synthesis methods for MOF coatings on functional materials are systematically summarized. Then, many potential applications of MOF coatings are highlighted and their structure-property correlations are discussed. Finally, the opportunities and challenges for the future research of MOF coatings are proposed. This review on the deep understanding of MOF coatings will bring better directions into the rational design of high-performance MOF-based materials and open up new opportunities for MOF applications.

Hydrophobic MOFs@Metal Nanoparticles@COFs for Interfacially Confined Photocatalysis with High Efficiency

Converting solar energy to chemical energy via photocatalysis has attracted increasing interest. Simultaneously realizing efficient charge separation and fast reactant/product diffusion/transport is highly significant for improving the photocatalytic activity, which however is difficult. Herein, we reported an interfacially confined strategy by constructing interfacial pores as nanoreactors between metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) with controlled surface wettability for efficient photocatalysis. In the sandwich Ti-MOFs@Pt@DM-LZU1, interfacial pores formed between Ti-MOF@Pt and DM-LZU1, in which Pt nanoparticles (NPs) were encapsulated. The presence of Pt facilitates the charge separation on the photoactive Ti-MOF, while the hydrophobic porous DM-LZU1 shell promotes reactant enrichment. Interfacial pores acting as nanoreactors ensure fast electron and mass transport between the active Pt NPs and the concentrated reactants, leading to high photocatalytic activity. This work presents a new concept for the design of various photocatalysts with considerable activity.

Modified MIL-100(Fe) for enhanced photocatalytic degradation of tetracycline under visible-light irradiation

Iron-based metal-organic frameworks (MOFs) with low cost and excellent photocatalytic potential are extremely attractive in the field of energy utilization and environmental remediation. In this study, a novel In₂S₃/MIL-100(Fe) photocatalyst was successfully synthesized by a facile solvothermal method for the first time. Several technologies (such as X-ray diffraction, scanning electron microscope, transmission electron microscope, and X-ray photoelectron spectroscopy) were used to characterize the as-obtained samples and demonstrate the successful combination of MIL-100(Fe) and In₂S₃. Experimental results showed that 18% of tetracycline (TC) was adsorbed under dark condition and another 70% of TC was degraded under visible-light irradiation when treating 100 mL of TC solution (10 mg/L) with 30 mg of In₂S₃/MIL-100(Fe) composites. The corresponding TC removal efficiency was almost 1.9 and 1.6 times higher than that of pure MIL-100(Fe) and In₂S₃, respectively. The mechanism investigations revealed that the heterojunction composite exhibited superior charge transfer than either MIL-100(Fe) or In₂S₃, and this caused more efficient separation of electron-hole pairs. As a result, more radicals and holes were generated in the composite, leading to better photocatalytic performance. This work highlights the powerful combination of MOFs and semiconductor, which is a promising approach to fabricate heterojunction photocatalyst for wastewater purification.

In situ photoreduction of structural Fe(III) in a metal-organic framework for peroxydisulfate activation and efficient removal of antibiotics in real wastewater

Structural Fe(III) is widely found in various coordination complexes and inorganic compounds. In this work, a typical Fe-based metal organic framework (MOF) (viz. MIL-100(Fe)) was chosen as an example in the activation of peroxydisulfate (PDS) for the removal of antibiotic pollutants. Interestingly, an auto-acceleration effect was observed in the process of MIL-100(Fe) activating PDS aided by visible light irradiation. Compared to the processes with MIL-100(Fe)-activated PDS alone and the photo-activated PDS alone, the degradation efficiency of sulfamethoxazole (SMX) obtained in the visible light assisted PDS activation by MIL-100(Fe) process was enhanced by 2.1 and 5.6 times, respectively. Therein, the photogenerated electrons from MIL-100(Fe) carried out an in situ reduction of the surface structural Fe(III) to form Fe(II), which in turn significantly improved the PDS activation efficiency in the generation of ·OH and O₂^-· radicals for the removal of SMX. The degradation pathways of SMX were deduced based on the experimental results and theoretical calculations. Acute toxicity estimation indicated the formation of less toxic products after the treatment of SMX. Additionally, degradation of five antibiotics in the real wastewater were investigated to further confirm the advantages of such in situ photoreduced structural Fe(III) in MOFs to activate the PDS process.

Selective Photocatalytic Oxidation of Thioanisole on DUT-67(Zr) Mediated by Surface Coordination

DUT-67(Zr) was obtained by a solvothermal route and applied to photocatalytic selective synthesis of thioanisole under light illuminating. The conversion of thioanisole is up to 95%, and the selectivity of methyl phenyl sulfoxide is 98%. The activity of DUT-67(Zr) is over 10 times higher than that of UiO-66. This great increased activity is attributed to the high percentages of oxygen vacancies on DUT-67(Zr). The ESR result shows there are more oxygen vacancies that can expose high density unsaturated Zr sites on DUT-67(Zr). The in situ FTIR reveals that unsaturated Zr sites on DUT-67(Zr) possess Lewis acidity which facilitate the adsorption of the substrates to form the coordination species, promoting the activation of thioanisole. The absorption edge of DUT-67(Zr) with coordination species red-shifts to 360 nm, which can be presented by DRS. Furthermore, the oxygen molecules can be activated by excited electrons to form ^•O₂^-. Finally, a possible photocatalytic process of oxidating thioanisole to methyl phenyl sulfoxide based on the coordination effect between DUT-67(Zr) and thioanisole is proposed at a molecular level.

Silver nanoparticles stabilized by a metal–organic framework (MIL-101(Cr)) as an efficient catalyst for imine production from the dehydrogenative coupling of alcohols and amines

In this paper, we present silver nanoparticles supported on a metal–organic framework (Ag@MIL-101) as a catalyst for the one-pot tandem synthesis of imines from alcohols and amines.

Synergistic Effect over Sub-nm Pt Nanocluster@MOFs Significantly Boosts Photo-oxidation of N-alkyl(iso)quinolinium Salts

Quinolones and isoquinolones are of interest to pharmaceutical industry owing to their potent biological activities. Herein, we first encapsulated sub-nm Pt nanoclusters into Zr-porphyrin frameworks to afford an efficient photocatalyst Pt_0.9@PCN-221. This catalyst can dramatically promote electron-hole separation and ¹O₂ generation to achieve synergistic effect first in the metal-organic framework (MOF) system, leading to the highest activity in photosynthesis of (iso)quinolones in >90.0% yields without any electronic sacrificial agents. Impressively, Pt_0.9@PCN-221 was reused 10 times without loss of activity and can catalyze gram-scale synthesis of 1-methyl-5-nitroisoquinolinone at an activity of 175.8 g·g_cat⁻¹, 22 times higher than that of PCN-221. Systematic investigations reveal the contribution of synergistic effect of photogenerated electron, photogenerated hole, and ¹O₂ generation for efficient photo-oxidation, thus highlighting a new strategy to integrate multiple functional components into MOFs to synergistically catalyze complex photoreactions for exploring biologically active heterocyclic molecules.

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A state-of-the-art photocatalyst for preparation of bioactive (iso)quinolones

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Synergistic catalysis of photogenerated e⁻/h⁺ and ¹O₂

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Sub-nm Pt_0.9@PCN-221 with a high efficiency of e⁻-h⁺ separation and ¹O₂ generation

Engineering Metal-Organic Framework Catalysts for C-C and C-X Coupling Reactions: Advances in Reticular Approaches from 2014-2018

Metal-organic frameworks (MOFs) are a class of crystalline porous materials that have been actively used for several industrial and synthetic applications. MOFs are spatially and geometrically extrapolated coordination polymers with intriguing properties such as tunable porosity and dimensionality. In terms of their catalytic efficiency, MOFs combine the easy recoverability of heterogeneous catalysts with the increased selectivity of biological catalysts. It is therefore not surprising that a lot of work on optimizing MOF catalysts for organic transformations has been carried out over the past decade. In this review, recent developments in MOF catalysis are summarized, with special attention being paid to C-C, C-N, and C-O coupling reactions. The influence of pore size, pore environment, and load on catalytic activity is described. Post-synthetic stabilization techniques and host-guest interactions in caged MOF scaffolds are detailed. Mechanistic aspects pertaining to the use of MOFs in asymmetric heterogeneous catalysis are highlighted and categorized.

MIL-100(Fe)/Ti3C2 MXene as a Schottky Catalyst with Enhanced Photocatalytic Oxidation for Nitrogen Fixation Activities

A new microporous MIL-100(Fe)/Ti₃C₂ MXene composite was constructed as a non-noble metal-based Schottky junction photocatalyst with improved nitrogen fixation ability. Ti₃C₂ MXene nanosheets exhibited excellent metal conductivity and were employed as two-dimensional support to optimize the composite's energy band structure. MIL-100(Fe) with a large specific surface area was used as an adsorbent and a photocatalytic oxidation center. The MIL-100(Fe)/Ti₃C₂ MXene composite not only exhibited higher thermal stability but also showed significantly increased nitrogen fixation activity under visible light. The NO conversion rate of the composite catalyst was about four and three times higher than that of the pure Ti₃C₂ MXene and the pure MIL-100(Fe) samples, respectively. Although adsorption plays an important role in the nitrogen fixation process, the synergistic effects of the Schottky junctions are the main cause of the enhanced photocatalytic activity. The built-in electric field can be generated to form charge-transfer channels, which help to achieve a desirable photocatalytic activity.

Metal Organic Frameworks as Robust Host of Palladium Nanoparticles in Heterogeneous Catalysis: Synthesis, Application, and Prospect

Metal organic frameworks (MOFs) are one set of the most excellent supports for Pd nanoparticles (NPs). MOFs as the host mainly have the following advantages: (i) they provide size limits for highly dispersed Pd NPs; (ii) fixing Pd NPs is beneficial for separation and reuse, avoiding the loss of expensive metals; (iii) the MOFs skeleton is diversified and functionalized, which is beneficial to enhancing the interaction with Pd NPs and prolonging the service life of the catalyst. This review discusses the synthesis strategy of Pd@MOF, which provides guidance for the synthesis of similar materials. After that, the research advance of Pd@MOF in heterogeneous catalysis is comprehensively summarized, including C-C coupling reaction, benzyl alcohol oxidation reaction, simple olefin hydrogenation reaction, nitroaromatic compound reduction, tandem reaction, and the photocatalysis, with the emphasis in providing a comparison with the performance of other alternative Pd-containing catalysts. In the final section, this review presents the current challenges and which are the next goals in this field.

Tailoring the Assembly of Iron Nanoparticles in Carbon Microspheres toward High-Performance Electrocatalytic Denitrification

Electrocatalytic denitrification is considered as the most promising technology to transform nitrates to nitrogen gas in sewage so far. Although noble metal-based catalysts as a cathode material have reached decent removal capacity of nitrate, the high cost is the main hamper of electrocatalytic reduction. Therefore, the development of alternative catalysis toward highly effective denitrification is imperative yet still remains a significant challenge. Herein, a corchorifolius-like structure, where Fe nanoparticles are sealed in carbon microspheres (CL-Fe@C) with a rough surface, has been elaborately designed by self-assemble strategy. Impressively, the architectured CL-Fe@C microspheres are surrounded with a lot of small iron nanoparticles and contain the high iron content of ∼74%. As a result, an excellent removal capacity of 1816 mg N/g Fe and a high nitrogen selectivity of 98% under a very low nitrate concentration of 100 mg/L are achieved when using the CL-Fe@C microspheres as electrocatalytic denitrification. The present work not only explores high performance electrocatalysis for the denitrification but also promote new inspiration for the preparation of other iron-based functional materials for diverse applications.

Integration of Metal Nanoparticles into Metal-Organic Frameworks for Composite Catalysts: Design and Synthetic Strategy

Metal-organic frameworks (MOFs) are constructed by periodically alternate metal ions with organic ligands, which offer structural diversity and a wide range of interesting properties as an attractive classification of crystalline porous materials. Integration of MOFs with other size-limited functional centers can supply new multifunctional composites, which exhibit both the properties of the components and new characteristics due to the combination of MOFs with the selected loadings. In recent years, integration of metal/metal oxide nanoparticles (MNPs) into MOFs to form the composite catalysts has attracted considerable attention due to the superior performance. In this review, the latest studies and up-to-date developments on the design and synthetic strategy of new MNP@MOF composite catalysts are specifically highlighted. Both the achievements and problems are evaluated and proposed, and the opportunities and challenges of MNP@MOF composite catalysts are discussed.