Direct Synthesis Research Articles

Fluorocarboxylic acid‐modified MOF‐808 with enhanced acetylene adsorption capacity and C2H2/C2H4 separation performance

The separation of ethylene (C2H4) and acetylene (C2H2) is challenging due to their similar molecular dimensions and boiling points, making conventional methods like cryogenic distillation and solvent extraction inefficient and environmentally harmful. Fluorinated metal‐organic frameworks (MOFs) have been proven to be an effective material for the separation of C2H4 and C2H2. However, their direct synthesis is relatively expensive and challenging. In this study, we report a facile post‐synthetic modification strategy to introduce fluorinated alkane pores into a zirconium‐based MOF, MOF‐808. The construction of fluorine‐containing pores within the MOFs prefers adsorption for C2H2 attributed to the interaction between the fluorine atoms and C2H2. This series of fluorinated MOFs demonstrates potential for gas separation processes, with the highest separation ratio reaching 2.67 (1:99) at 298K. Breakthrough experiments for C2H2/C2H4 mixtures confirmed that fluorinated MOF is capable of separating C2H2/C2H4, making it a potential candidate for industrial application. Moreover, the simplicity of the post‐synthetic modification method suggests a viable strategy for the synthesis of fluorinated MOFs.

Reductive Coupling of N-Heteroarenes and 1,2-Dicarbonyls for Direct Access to γ-Amino Acids, Esters, and Ketones Using a Heterogeneous Single-Atom Iridium Catalyst.

Despite their significant importance, the challenges in direct and diverse synthesis of N-heterocyclic γ-amino acids/esters/ketones hamper exploration of their applications. Herein, by developing a multifunctional heterogeneous iridium single-atom catalyst composed of silica-confined iridium species and a boron-doped ZrO2 support (Ir-SAs@B-ZrO2/SiO2), we describe its utility in establishing a new reductive coupling reaction of N-heteroarenes and 1,2-dicarbonyls for selective and diverse construction of the as-described compounds in a straightforward manner. The striking features, including good substrate and functionality tolerance, high step and atom economy, exceptional catalyst reusability, and diversified product post-transformations, highlight the practicality of the developed chemistry. Mechanistic studies reveal that the synergy between the active Ir sites and acidic support favors a chemoselective reduction of the more inert N-heteroarenes and affords requisite enamine intermediates. In this work, the concept on precise transformation of reductive intermediates will open a door to further develop useful tandem reactions by rational catalyst design.

Direct Synthesis of Benzhydryl-Functionalized 3,4-Dihydropyridin-2-ones from 2-Pyridones and Their Use in the Formation of Bridged δ-Lactams

A method for the synthesis of C4-benzhydryl-functionalized 3,4-dihydropyridin-2-ones using complementary addition of benzhydryllithium and/or benzhydrylmagnesiate reagents to 2-pyridones, with high regioselectivity triggered by substituents, is described. A partially stereoselective cyclization was successfully demonstrated using TfOH and/or TIPSOTf as Brønsted and Lewis acids, respectively, leading to C6-phenyl-functionalized 7,8-benzomorphanones. It is also shown that the use of functionalized δ-enelactams obtained with an active methoxy-substituted benzyl group at C3 enabled the preparation of a new C3–C6 bridged system within the δ-lactam framework.

Direct Synthesis of H2O2 over AuCu@AuPd Core–Shell Catalysts with Highly Dispersed Pd Sites

Direct Synthesis of H₂O₂ over AuCu@AuPd Core–Shell Catalysts with Highly Dispersed Pd Sites

Electrocatalysts for the Formation of Hydrogen Peroxide by Oxygen Reduction Reaction.

Hydrogen peroxide (H2O2) is a widely used strong oxidant, and its traditional preparation methods, anthraquinone method, and direct synthesis method, have many drawbacks. The method of producing H2O2 by two-electron oxygen reduction reaction (2e- ORR) is considered an alternative strategy for the traditional anthraquinone method due to its high efficiency, energy saving, and environmental friendliness, but it remains a big challenge. In this review, we have described the mechanism of ORR and the principle of electrocatalytic performance testing, and have summarized the standard performance evaluation techniques for electrocatalysts to produce H2O2. Secondly, according to the theoretical calculation and experimental results, several kinds of efficient electrocatalysts are introduced. It is concluded that noble metal-based materials, carbon-based materials, non-noble metal composites, and single-atom catalysts are the preferred catalyst materials for the preparation of H2O2 by 2e- ORR. Finally, the advantages and novelty of 2e- ORR compared with traditional methods for H2O2 production, as well as the advantages and disadvantages of the above-mentioned high-efficiency catalysts, are summarized. The application prospect and development direction of high-efficiency catalysts for H2O2 production by 2e- ORR has been prospected, which is of great significance for promoting the electrochemical yield of H2O2 and developing green chemical production.

Recent Progress in Situ Application of H2O2 Produced via Catalytic Synthesis.

Industrial production of H2O2 requires lots of energy and causes environmental pollution. Moreover, in subsequent applications, much economic loss could be produced during the transportation process of H2O2 and its dilution process. Therefore, it is highly desirable for in situ application of H2O2. In recent years, catalytic synthesis of H2O2, e. g., direct catalytic synthesis, electrocatalytic synthesis, and photocatalytic synthesis, has attracted more and more attention because the continuous and low-concentration H2O2 produced by catalytic synthesis can be directly used for the oxidation of organic compounds, effectively avoiding the shortcomings of the current industrial route. Here, we briefly reviewed the latest processes for the catalytic production of H2O2 via various routes. On this basis, we summarized and discussed the in situ application of H2O2 in typical organic conversion reactions, including the ammoximation of ketones, the oxidation of alcohols, the oxidation of C-H bonds, and the oxidation of olefins. Some in situ coupling reactions have shown excellent performance with high conversion and selectivity, and the economic cost has been significantly reduced. Finally, the shortcomings of the in situ utilization of H2O2 in coupling reactions were analyzed, and some strategies for promoting the efficiency of the H2O2 application in organic synthesis were proposed.

Combination of Hollow Capsule Structure and Zn Uniform Load for the Conversion of Methanol to Aromatics over Zn/ZSM-5 Zeolites.

As an important nonoil route for acquiring aromatics, the highly efficient conversion of methanol to aromatics over Zn/ZSM-5 zeolites remains an ongoing challenge. In this work, we developed a uniform loading approach of zinc and further combined it with a hollow capsule structure to design the high-performance Zn/ZSM-5 catalyst. The electrostatic assembly among EDTA3-, n-butylamine+ and negative silica-alumina gel gave rise to an "Inorganic-Organic Hybrid Sphere" in form of Na(l+m+n+3x)-(y+z)·{[(SiO)4Al-]l/(SiO-)m(n-butylamine+)y(EDTA3-)x(n-butylamine+)z(SiO-)n, which further transformed into mesoporous aluminosilicates sphere (MASS) through calcination. The characteristic of abundant mesopore guaranteed MASS fantastic ability to evenly incorporate Zn ingredient inside, and the resultant Zn/MASS further served as a "hard template" for the direct synthesis of Hollow Zn/ZSM-5 capsules, rather than after impregnation. When tested in the methanol-to-aromatics (MTA) process, the direct synthesis method not only facilitated the homogeneous dispersion of the Zn ingredient, but also benefited for the generation of more (ZnOH)+ sites and strengthened their synergism with zeolite acid for the superior aromatics selectivity (50.63%). Meanwhile, the hollow capsule structure increased the contact time of MTA intermediate products with the Zn/ZSM-5 shell, and it increased the coke-admitting capacity and suppressed the coke rate, which maintained quite an excellent stability (131 h). Therefore, the above combination of hollow capsule structure and uniform load of Zn ingredient brings forward a wide prospect to develop zeolite materials with excellent properties in catalysis.

Direct Synthesis of N-Fused Indoles Enabled by Copper-Catalyzed Aerobic Oxygenative Rearrangement

Direct Synthesis of <i>N</i>-Fused Indoles Enabled by Copper-Catalyzed Aerobic Oxygenative Rearrangement

Integrated Ziegler-Natta/Brookhart-Ni Catalysts for the Synthesis of Sutured Polar High-Impact Polypropylenes.

The direct synthesis of polar high-impact polypropylenes using industrially-preferred heterogeneous catalysts is challenging due to the poisoning of polar functional groups towards metal center and the high stereo-selectivity requirement. In this work, dual-site catalysts combining Ziegler-Natta and Brookhart-Ni catalysts were used to produce polar polyolefin ionomers, followed by polar high-impact polypropylenes containing isotactic polypropylene and branched polyethylene as toughening agents. Three combination modes between these catalysts were investigated, including mixed, core-shell, and integrated types. The integrated dual-site catalyst achieved the optimal material properties because the polyolefin ionomer acted as a suture molecule that stitched different components into a whole network. This produced sutured polar high-impact polypropylenes with excellent mechanical properties and compatibility with polar substances. The restraining effect of the suture molecules greatly reduced the release of microplastic particles after aging. Moreover, the obtained polar high-impact polypropylene can serve as an efficient compatibilizer to recycle polyethylene/polypropylene mixed-waste plastics. This work provides an appealing and potentially practical strategy to upgrade the widely used polypropylenes and to alleviate the ever-growing plastic pollution issue.

Integrated Ziegler‐Natta/Brookhart‐Ni Catalysts for the Synthesis of Sutured Polar High‐Impact Polypropylenes

The direct synthesis of polar high‐impact polypropylenes using industrially‐preferred heterogeneous catalysts is challenging due to the poisoning of polar functional groups towards metal center and the high stereo‐selectivity requirement. In this work, dual‐site catalysts combining Ziegler‐Natta and Brookhart‐Ni catalysts were used to produce polar polyolefin ionomers, followed by polar high‐impact polypropylenes containing isotactic polypropylene and branched polyethylene as toughening agents. Three combination modes between these catalysts were investigated, including mixed, core‐shell, and integrated types. The integrated dual‐site catalyst achieved the optimal material properties because the polyolefin ionomer acted as a suture molecule that stitched different components into a whole network. This produced sutured polar high‐impact polypropylenes with excellent mechanical properties and compatibility with polar substances. The restraining effect of the suture molecules greatly reduced the release of microplastic particles after aging. Moreover, the obtained polar high‐impact polypropylene can serve as an efficient compatibilizer to recycle polyethylene/polypropylene mixed‐waste plastics. This work provides an appealing and potentially practical strategy to upgrade the widely used polypropylenes and to alleviate the ever‐growing plastic pollution issue.

Integrating Compositional and Structural Diversity in Heterometallic Titanium Frameworks by Metal Exchange Methods.

The increasing use of Metal-Organic Frameworks (MOFs) in separation, catalysis, or storage is linked to the targeted modification of their composition or porosity metrics. While modification of pore shape and size necessarily implies the assembly of alternative nets, compositional changes often rely on postsynthetic modification adapted to the functionalization or exchange of the organic linker or the modification of the inorganic cluster by metal exchange methods. We describe an alternative methodology that enables the integration of both types of modification, structural and compositional, in titanium MOFs by metal exchange reaction of the heterometallic cluster Ti2Ca2. A systematic analysis of this reactivity with MUV-10 is used to understand which experimental variables are crucial to enable replacement of calcium only or to integrate metal exchange with structural transformation. The isoreticular expanded framework, MUV-30, is next used to template the formation of MUV-301, a titanium framework not accessible by direct synthesis that displays the largest mesoporous cages reported to date. Given that the interest of Ti MOFs in photoredox applications often meets the limitations imposed by the challenges of titanium solution chemistry to design concrete candidates, this soft strategy based on preassembled frameworks will help integrate specific combinations of metals into high porosity architectures.

Unveiling the Pivotal Role of Ce Coordination Structures and Their Surface Arrangements in Governing 2-Cyanopyridine Hydrolysis for Direct Dimethyl Carbonate Synthesis from CO2 and Methanol

Unveiling the Pivotal Role of Ce Coordination Structures and Their Surface Arrangements in Governing 2-Cyanopyridine Hydrolysis for Direct Dimethyl Carbonate Synthesis from CO₂ and Methanol

Platelet Ceria Catalysts from Solution Combustion and Effect of Iron Doping for Synthesis of Dimethyl Carbonate from CO2.

Solution combustion (SC) remains among the most promising synthetic strategies for the production of crystalline nanopowders from an aqueous medium, due to its easiness, time and cost-effectiveness, scalability and eco-friendliness. In this work, this method was selected to obtain anisometric ceria-based nanoparticles applied as catalysts for the direct synthesis of dimethyl carbonate. The catalytic performances were studied for the ceria and Fe-doped ceria from SC (CeO2-SC, Ce0.9Fe0.1O2-SC) in comparison with the ceria nanorods (CeO2-HT, Ce0.9Fe0.1O2-HT) obtained by hydrothermal (HT) method, one of the most studied systems in the literature. Indeed, the ceria nanoparticles obtained by SC were found to be highly crystalline, platelet-shaped, arranged in a mosaic-like assembly and with smaller crystallite size (≈6 nm vs. ≈17 nm) and higher surface area (80 m2 g-1 vs. 26 m2 g-1) for the undoped sample with respect to the Fe-doped counterpart. Although all samples exhibit an anisometric morphology that should favor the exposition of specific crystalline planes, HT-samples showed better performances due to higher oxygen vacancies concentration and lower amount of strong basic and acid sites.

Masked second-shell sulfur coordinating atomically dispersed Pd on tin oxide boosts the direct synthesis of hydrogen peroxide

Masked second-shell sulfur coordinating atomically dispersed Pd on tin oxide boosts the direct synthesis of hydrogen peroxide

Integrating Metal–Organic Frameworks and Polyamide 12 for Advanced Hydrogen Storage Through Powder Bed Fusion

This paper introduces a pioneering approach that combines ex situ synthesis with advanced manufacturing to develop ZIF-67-PA12 Nylon composites with mixed-matrix membranes (MMMs), with the goal of enhancing hydrogen storage systems. One method involves producing MOF-PA12 composite powders through an in situ process, which is then commonly used as a base powder for powder bed fusion (PBF) to fabricate various structures. However, developing the in situ MOF-PA12 matrix presents challenges, including limited spreadability and processability at higher MOF contents, as well as reduced porosity due to pore blockage by polymers, ultimately diminishing hydrogen storage capacity. To overcome these issues, PBF is employed to form PA12 powder into films, followed by the ex situ direct synthesis of ZIF-67 onto these substrates at loadings exceeding those typically used in conventional MMM composites. In this study, ZIF-67 mass loadings ranging from 2 to 30 wt.% were synthesized on both PA12 powder and printed film substrates, with loadings on printed PA12 films extended up to 60 wt.%. ZIF-67-PA12-60(f) demonstrated a hydrogen capacity of 0.56 wt.% and achieved 1.53 wt.% for ZIF-67-PA12-30(p); in comparison, PA12 exhibited a capacity of 0.38 wt.%. This was undertaken to explore a range of ZIF-67 Metal–organic frameworks (MOFs) to assess their impact on the properties of the composite, particularly for hydrogen storage applications. Our results demonstrate that ex situ-synthesized ZIF-67-PA12 composite MMMs, which can be used as a final product for direct application and do not require the use of in situ pre-synthesized powder for the PBF process, not only retain significant hydrogen storage capacities, but also offer advantages in terms of repeatability, cost-efficiency, and ease of production. These findings highlight the potential of this innovative composite material as a practical and efficient solution for hydrogen storage, paving the way for advancements in energy storage technologies.

Direct Introduction of Perfluoroacyl (−CORF) Groups into Organic Substrates

AbstractThe direct addition of perfluoroacyl (−CORF) groups to organic frameworks has seen a resurgence in interest due to the benefits of these groups in late‐stage modification of pro‐drugs and biologically active compounds, helping to identify new active leads. The presence of −CORF groups positively impacts the structure‐activity relationships of these compounds. In that sense, both polar methods and radical protocols have been developed for the direct syntheses of trifluoromethyl and perfluoroalkyl ketones. In particular, methodologies to tame the unstable trifluoroacyl radical, which could be a key intermediate in the late‐stage syntheses of trifluoroacyl‐substituted compounds, has allowed much progress in this area. In the next sections, the direct incorporation of perfluoroacyl groups into (hetero)aromatic compounds, −CORF substitutions at Csp3−H, alkyl halides, alkenes, amides, and N‐atoms will be discussed in detail, suggesting the future directions and perspectives in the field. These known reactions are summarized in Table 1.

Photocatalytic Synthesis of Glycine from Methanol and Nitrate

AbstractPhotocatalytic utilization of methanol and nitrate as carbon and nitrogen sources for the direct synthesis of amino acids could provide a sustainable way for the valorization of green “liquid sunlight” and nitrate waste. In this study, we develop an efficient photochemical method to synthesize glycine directly from methanol and nitrate, which cascades the C−C coupling to form glycol, nitrate reduction to NH3, and finally C−N coupling to generate glycine. Interestingly, the involved photocatalytic tandem reactions show a synergistic effect, in which the presence of nitrate is the dominant factor to enable the overall reaction and reach high synthetic efficiency. Ba2+−TiO2 nanoparticles are confirmed as a feasible and efficient catalyst system for the photosynthesis of glycine with a remarkable glycine photosynthesis rate of 870 μmol gcat−1 h−1 under optimal conditions. This work establishes a novel catalytic system for amino acid synthesis from methanol and nitrate under mild conditions. These results also allow us to further suppose the formation pathways of amino acids on the primitive earth, as an extension to proposals based on the Miller‐Urey experiments.

Microemulsion Templating Synthesis of Hierarchical Porous Ag‐Doped SiO2‐TiO2 Composites for Efficient Degradation of Noxious Methylene Blue Dye: Effect of Calcination Environment

AbstractWe report herein a dual function mesoporous structure of titanium oxide based porous carbon with large surface‐to‐volume ratios for efficient degradation of noxious methylene blue dye (MB) from an aqueous environment. The mesoporous photocatalysts is fabricated via direct template synthesis of highly ordered silica‐titania monolith doped with Ag0/Ag2O starting from a quaternary microemulsion liquid crystalline phase. The produced monoliths are subjected in‐situ to doping by growing silver, in the cubic cavities, and on the silica/titania structure's domain. This study investigated the efficiency of novel composite materials, consisting of silver‐doped silica‐titania (SiO2/TiO2), which is synthesized using the microemulsion templating approach. The photocatalytic performance of the synthesized composite in the photodegradation of MB has been studied. The procedure of photodegradation was employed to achieve decolorization of the cationic MB dye using visible light. The catalyst effectively achieved the decolorization of the dyed solution through the processes of adsorption and photodegradation. The composite consisting of SiO2, TiO2, and Ag2O at a ratio of 1 : 1:0.5, which underwent calcination in an air environment (AgOST), exhibited a removal efficiency of 99 % compared to its calcined state under argon (AgSTC).

Mechanism study on the influence of surface properties on the synthesis of dimethyl carbonate from CO2 and methanol over ceria catalysts

The direct synthesis of dimethyl carbonate (DMC) from CO2 and methanol has attracted much attention as an environmentally benign and alternative route for conventional routes. Herein, a series of cerium oxide catalysts with various textural features and surface properties were prepared by the one-pot synthesis method for the direct DMC synthesis from CO2 and methanol, and the structure-performance relationship was investigated in detail. Characterization results revealed that both of surface acid-base properties and the oxygen vacancies contents decreased with the rising crystallinity at increasingly higher calcination temperature accompanied by an unexpectedly volcano-shaped trend of DMC yield observed on the catalysts. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) studies indicated that the adsorption rate of methanol is slower than that of CO2 and the methanol activation state largely influences the formation of key intermediate. Although the enhanced surface acidity-basicity and oxygen vacancies brought by low-temperature calcination could facilitate the activation of CO2, the presence of excess strongly basic sites on low-crystallinity sample was detrimental to DMC synthesis due to the preferred formation of unreactive mono/polydentate carbonates as well as the further impediment of methanol activation. Moreover, with the use of 2-cyanopyridine as a dehydration reagent, the DMC synthesis was found to be both influenced by the promotion from the rapid in situ removal of water and the inhibition from the competitive adsorption of hydration products on the same active sites.

Metal-Based Oxygen Reduction Electrocatalysts for Efficient Hydrogen Peroxide Production.

Hydrogen peroxide (H2O2) is a high-value chemical widely used in electronics, textiles, paper bleaching, medical disinfection, and wastewater treatment. Traditional production methods, such as the anthraquinone oxidation process and direct synthesis, require high energy consumption, and involve risks from toxic substances and explosions. Researchers are now exploring photochemical, electrochemical, and photoelectrochemical synthesis methods to reduce energy use and pollution. This review focuses on the 2-electron oxygen reduction reaction (2e- ORR) for the electrochemical synthesis of H2O2, and discusses how catalyst active sites influence O2 adsorption. Strategies to enhance H2O2 selectivity by regulating these sites are presented. Catalysts require strong O2 adsorption to initiate reactions and weak *OOH adsorption to promote H2O2 formation. The review also covers advances in single-atom catalysts (SACs), multi-metal-based catalysts, and highlights non-noble metal oxides, especially perovskite oxides, for their versatile structures and potential in 2e- ORR. The potential of localized surface plasmon resonance (LSPR) effects to enhance catalyst performance is also discussed. In conclusion, emphasis is placed on optimizing catalyst structures through theoretical and experimental methods to achieve efficient and selective H2O2 production, aiming for sustainable and commercial applications.