Reaction Chemistry & Engineering最新文献

Even after decades of industrial use, the fundamental factors governing the selectivity of acidic extractants for various divalent metal ions in the fourth period of the periodic system have not yet been identified. In this paper, the case is made for ligand field stabilization energy as the principal quantity determining the extractability of a divalent metal ion by a particular acidic extractant. This stabilizing energetic contribution results from non-isotropic (covalent) interactions between the metal ion and the extractant, which acts as an inner-sphere ligand in the metal-extractant complex. The extractability of a metal ion appears to be largely determined by the difference in ligand field stabilization energy in the organic versus the aqueous phase. In order to investigate this correlation, the magnitude of the splitting of the d-orbitals in the metal-extractant complexes was probed by ultraviolet-visible-near-infrared absorption spectroscopy. Crystal field theory was applied to estimate the anisotropic contribution to the stability of each metal-extractant combination (ligand field stabilization energy), and of the hydrated metal ion in the aqueous phase. It was found that the anisotropic contribution is diminished upon extraction by extractants that weakly split the d-orbitals. This leads to preferential extraction of metal ions in which the electron configuration results in zero covalent contribution. Conversely, the anisotropic contribution becomes more favorable upon extraction by extractants which induce a large splitting of the d-orbitals. Hence, these extractants preferentially extract metal ions with a large covalent contribution to the total energy balance. Extractants with an intermediate splitting of d-orbitals exhibit little difference in covalent stabilization between both phases, and hence the extraction sequence is primarily determined by electrostatic effects, governed by the charge density of the metal ion. The model was applied to phosphoric, phosphonic, phosphinic, dithiophosphinic and carboxylic acid extractants, as well as to β-diketone and β-hydroxyketoxime extractants.

Correction for ‘Photocatalytic butanol reforming for hydrogen production using Ag₂O/TiO₂ composite catalysts: effects of Ag₂O loading, calcination temperature, and reaction parameters’ by Tumelo Seadira et al., React. Chem. Eng., 2026, https://doi.org/10.1039/d5re00384a.

Solar-driven CO₂ conversion into valuable chemicals is a promising strategy for sustainable energy and carbon management. In this work, a visible-light-active covalent organic framework (Btc–Bpy COF) film was synthesized via an interfacial strategy and evaluated as a photocatalyst for CO₂ reduction to formic acid with coupled photo-redox co-factor cycling. The pristine COFs exhibited efficient photocatalytic performance, achieving formic acid production of 196.93 μM with 82.74% co-factor cycling (1,4-NADH) under visible-light irradiation. To further enhance catalytic efficiency, a rhodium-complex-integrated COF complex (Btc–Bpy–Rh COFC) was developed via post-synthetic metal coordination, while retaining the integrity of the covalent framework. The incorporation of rhodium provided well-defined catalytic sites and improved interfacial charge dynamics, resulting in enhanced activity and selectivity, with formic acid production up to 225.62 μM and 88.82% co-factor cycling. This study demonstrates that the interfacial engineering of COFs via rhodium-complex integration is an effective approach for improving photocatalytic CO₂ reduction and co-factor cycling, serving as a benchmark example, marking the first reported use of this streamlined system for establishing a new standard for future advancements. Comprehensive spectroscopic and electrochemical analyses, including UV-vis diffuse reflectance spectroscopy, steady state and time-resolved photoluminescence, N₂ adsorption–desorption, and electrochemical studies, were employed to investigate the optical properties, charge-transfer dynamics, and surface characteristics of the photocatalysts.

Over recent years, photocatalytic biomass reforming for hydrogen production has gained research attention as an alternative to the inefficient water-splitting reaction, which requires a standard Gibbs free energy of 237 kJ mol⁻¹. In this study, anatase-phase titanium dioxide (TiO₂) particles were successfully synthesized by employing a sol–gel method, and silver oxide (Ag₂O) nanoparticles with different weight percentages were loaded on the surface of TiO₂via an incipient wet impregnation method to form composite photocatalysts. The structural and optical properties, specific surface areas, and morphology of the photocatalysts were investigated using X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), Brunauer–Emmett–Teller (BET), and scanning electron microscopy (FESEM) analyses. The photocatalytic hydrogen activity of the prepared photocatalysts was studied under visible light irradiation, and it was found that varying the Ag₂O loading influenced this activity. Furthermore, it was found that the calcination temperature and reaction parameters, such as pH and initial butanol concentration, influenced the photocatalytic activity of the prepared photocatalysts for efficient hydrogen production. The highest photocatalytic hydrogen production efficiency was achieved with 0.5 wt% Ag₂O/TiO₂ composite photocatalyst (290 mmol g_cat⁻¹). This activity was attributed to 100% anatase crystallite TiO₂ particles that are highly active in terms of the photogeneration of charge carriers; the uniform distribution of Ag₂O on the TiO₂ surface enhanced the suppression of charge-carrier recombination. Finally, the slightly acidic conditions of the butanol mixture facilitated the efficient adsorption of butanol on the surface of the photoexcited photocatalysts, resulting in the simultaneous rapid oxidation of butanol and the efficient production of hydrogen molecules.

The isoxazoline skeleton is a pivotal structural motif in pharmaceuticals and agrochemicals, necessitating the development of efficient synthetic methodologies. Conventional synthesis via 1,3-dipolar cycloaddition often requires multiple steps to prepare nitrile oxide precursors. While acid–base catalysis offers a more direct route from α,β-unsaturated aldehydes and ketoximes, catalyst recovery remains a significant challenge. In this study, we developed robust heterogeneous acid–base catalysts by immobilizing aminobenzenesulfonic acids—inexpensive dye precursors—onto polystyrene. These catalysts effectively promote the synthesis of isoxazolines from α,β-unsaturated aldehydes and acetoximes. Notably, the catalyst system is highly compatible with continuous flow reactions, maintaining yields above 70% for over 50 hours of operation. Mechanistic investigations, supported by DFT calculations, reveal two distinct, isomer-dependent pathways: (i) an iminium-mediated 1,4-addition for the 2-aminobenzenesulfonic acid-immobilized catalyst, and (ii) a concerted acid–base activation enabling direct 1,4-addition for the 3-amino isomer.

Octacalcium phosphate (OCP) allows substitution of HPO₄²⁻ in the hydrated layer with dicarboxylate ions. We investigated the thermal behavior of pyrazole-3,5-dicarboxylic acid (PD)-substituted OCP. The substitution suggested the localized conversion toward an apatite-like structure upon heating in low-temperature region, indicating that hydrogen-bonding network modulated by PD influence the conversion features.

Glucaric acid, a high-value platform compound derived from renewable resources, has garnered increasing attention due to its broad applications in food additives, pharmaceutical precursors, and green chemical industries. Compared to traditional chemical synthesis routes that rely heavily on strong oxidizing agents, the associated high energy consumption and environmental pollution have become increasingly prominent concerns. As a result, microbial biosynthesis has emerged as a more sustainable and environmentally friendly alternative. In recent years, the rapid advances in metabolic engineering, synthetic biology, and systems biology have propelled Saccharomyces cerevisiae into the spotlight as a promising microbial host for glucaric acid production, owing to its well-characterized genetic background, robust expression systems, and excellent adaptability to industrial fermentation environments. This review provides a comprehensive overview of the current progress in engineering microbial strains for glucaric acid production, highlighting strategies for pathway construction and optimization, including functional enhancement of key enzymes, metabolic flux redistribution, and host stress-response modulation. Furthermore, recent developments in fermentation process optimization and downstream purification techniques are summarized. The article also explores the potential of glucaric acid in emerging applications such as biodegradable materials, biopharmaceuticals, and sustainable chemicals. Future research should prioritize the integration of innovative biotechnological strategies with scalable manufacturing processes to fully realize the industrial potential of glucaric acid within a framework of environmental sustainability and economic viability.

A mobile microplasma jet was used for the direct, reductant-free, and controlled synthesis of silver/graphene nanocomposites. These nanocomposites were integrated with polydimethylsiloxane to construct flexible strain sensors. The correlation between AgNP content and sensor performance was systematically investigated. The Ag/Gr-16.9% sample exhibited high sensitivity and excellent durability, showing an overall stable ΔR/R₀ under 800 stretching cycles at 200% strain (10 mm s⁻¹) with only a slight decline. The sensor enabled reliable motion monitoring, including finger bending with a relative resistance change of ∼500%, and knee bending/extension at 15°, 30°, 45°, 60°, and 75° with ΔR/R₀ changes of ∼470%, 870%, 890%, 1000%, and 980%, respectively. These results highlight the sensor's capacity to track joint kinematics and bone-related mechanical loading. This work demonstrates a green and transfer-free route for in situ fabrication of Ag/Gr nanocomposites, providing guidance for constructing high-performance flexible strain sensors tailored for human motion monitoring and orthopedic diagnostic applications.

High magnetic fields have emerged as a powerful means for enabling controllable chemical reactions. However, the efficient integration of parallel reactors under high magnetic fields remains a significant challenge in reaction engineering. In this work, pneumatically-stirred parallel reactors capable of operating under a 10 T magnetic field were developed using 3D printing technology. Through a pneumatic actuation-based design, the device redesigns a single long stirring rod (1500 mm) into two shorter rods (each 120 mm), increasing the theoretical natural frequency and critical rotational speed by approximately 39-fold, thereby enhancing mechanical stability. The parallel reactor array enables synchronized stirring of four reaction cells within a single batch, thereby increasing experimental throughput by approximately 400% compared with a conventional single-reactor system. When operated under a 10 T magnetic field, the system maintains excellent stirring stability, with a relative speed deviation below 3.5%. The device was successfully applied to McMurry coupling, improving the trans/cis ratio of TPE–2NH₂ from 50 : 50 to 71 : 29. To the best of our knowledge, this work represents the first pneumatically-stirred parallel reactors enabling efficient chemical synthesis under high magnetic fields, offering valuable design insights for magnetically controlled synthesis equipment.

Acid–base sites are critical for catalytic transfer hydrogenation of furfural to furfuryl alcohol via the Meerwein–Ponndorf–Verley (MPV) reduction. Zirconium-based metal–organic frameworks contain abundant acid–base sites and show high activity in MPV reduction. Here, we report two distinct strategies to prepare defective MOF-808 (denoted as MOF-808-II_x and MOF-808-I_y) through partial substitution of tricarboxylate ligands with dicarboxylate or monocarboxylate ligands. Structural and physicochemical properties of the defective MOF-808 catalysts were systematically analyzed. Linker defects introduced additional acid–base sites at missing-linker nodes compared to pristine MOF-808, leading to significantly enhanced catalytic activity in MPV reduction of furfural. Furfural conversion increased from 72.9% (pristine MOF-808) to 85.3% (MOF-808-II₁₀) and 94.7% (MOF-808-I₄₀). The defective MOF-808 catalysts maintained activity over five consecutive cycles without significant deactivation, and a plausible reaction mechanism was proposed.