RSC Mechanochemistry最新文献

Complex molybdates are traditionally prepared via solid-state synthesis and aqueous chemistry methods, which generally require long reaction times and large solvent volumes or high sintering temperatures. However, these techniques often result in undesired secondary species, incomplete reactions, and relatively low yields. Mechanochemistry has proven effective for the synthesis of complex molybdates. This work expands on the development of the mechanochemical synthesis of various heptamolybdates (i.e., sodium, rubidium, and cesium), and trimolybdates (i.e., sodium, rubidium, cesium, strontium, and barium). The obtained materials were characterized via powder X-ray diffraction, Fourier-transform infrared spectroscopy, Raman spectroscopy, thermo-gravimetric analysis, and scanning electron microscopy to assess the purity, morphology, and quality of the sample. High purity samples of the various trimolybdates and heptamolybdates were obtained in less than three hours of reaction time, with minimal energy input and by-products. Mechanochemistry provides a fast, more sustainable, and simple procedure for the synthesis of a wide variety of both trimolybdates and heptamolybdates including the monohydrate form of sodium trimolybdate instead of the trihydrate variant commonly obtained from aqueous reactions.

An efficient diazotization of phenolic compounds with aryltriazenes is herein demonstrated by employing ball milling under catalyst-, promoter- and solvent-free conditions. The present protocol offers several advantages including mild conditions, good selectivity and high yields, simple operation and practical gram-scale synthesis. Overall, this novel strategy significantly improves the reaction efficiency, simplifies purification procedures of the diazotization reaction and provides potential for the industrial preparation of azo dyes.

Ball milling stands as a versatile and widely used technique that involves the mechanical grinding of solid materials via ball mills. Conventionally employed for synthesizing nanomaterials and complex compounds, this method has now been harnessed directly for catalysis due to its capability for surface charge separation. Herein, in the present study, we have explored the potential of ball milling to activate material with low piezoelectric coefficient for catalysis by demonstrating the ball-milling-induced mechano-catalytic activity of SrTiO₃ (STO) nanoparticles for the degradation of toxic methylene blue (MB) dye. With the assistance of ball milling, STO nanoparticles (of 0.3 g dosage) were found capable of degrading 70% of 10 ppm MB dye at 400 rpm speed with 10 Zr balls in just 1 hour. A series of parametric studies were performed to analyze the effect of various process conditions, like catalyst dosage, initial concentration of dye, ball milling speed, and number of milling balls. Further, scavenging tests were carried out to detect the responsible reactive species for dye degradation. Moreover, the present ball milling process was compared with the trivial ultrasonication method where STO showed just 12% degradation in 1 hour. The results manifest the superiority of ball milling catalysis which not only offers precise control over reaction parameters but also encompasses scalability, simplicity, and better potential to conduct catalysis under environmentally benign conditions.

We analyze the effect of pressure on the Diels–Alder (D–A) dimerization reactions using Evans–Polanyi (E–P) theory, a thermodynamic analysis of the way in which a perturbation, in this case a hydrostatic pressure, modifies a reaction rate. Because it is a thermodynamic analysis, the results depend only on the volumes of the initial- and transition-state structures and not on the pathways between them. The volumes are calculated by enclosing the initial- and transition-state structures in a van der Waals' cocoon. Pressure is exerted by multiplying the van der Waals' radii by some factor without allowing the initial- and transition-state structures to relax. The influence of the surrounding solvent is included by using the extreme-pressure, polarizable-continuum method (XP-PCM). The approach is illustrated in detail using cyclopentadiene dimerization for which the rates have been independently measured by two groups. The analysis provides results that are in good agreement with those found experimentally for measurements made up to ∼0.3 GPa. The activation volumes of other D–A reactions are calculated in the same way and lead to good agreement for non-polar reactants, but less good agreement for polar ones. The pressure can also distort the initial- and transition-state structures, which can be calculated from the initial- and transition-state Hessians. A pressure-dependent distortion requires knowing the area over which the hydrostatic pressure acts. This is obtained using the Stearn–Eyring postulate that the activation volume is the product of an activation length and the area over which the stress acts. The activation length is obtained from quantum calculations of the difference in the distances between the diene and dienophile in the initial- and transition states. This provides only minor corrections to the results for routinely accessible hydrostatic pressures.

Extracting edible nutrient-rich food fractions from unconventional sources, such as grass, could play a pivotal role in ensuring food security, bolstering economic prosperity, combating climate change, and enhancing overall quality of life. Current extraction techniques rely heavily on harsh chemicals, which not only degrade nutrients but can also substantially add to the cost of the process and make downstream separation challenging. In this study, we harnessed a mechanochemical process, liquid-assisted grinding (LAG) with and without Na₂CO₃, termed sodium carbonate assisted grinding (SAG), to extract the protein fraction from moor grass. These techniques were compared to the conventional alkaline extraction (AE) method. Unlike alkaline extraction, which solubilized over 70% of the material, the mechanochemical approach using Na₂CO₃ solubilized only 55% of the grass while still extracting the vast majority of the protein in the original grass feedstock. The protein fractions obtained from the SAG process had a similar amino acid profile to the core feedstock but also contained distinct characteristics over the other methods of extraction. FT-IR analysis, for example, identified the presence of an amide III band in the protein fractions obtained from the SAG process, indicating unique structural features that contribute to improved dispersibility, gelation properties, and water-in-water stability. Furthermore, the extracted moor grass protein contained a higher proportion of glutamic acid in comparison to other amino acids in the protein, which indicates a savoury umami (meaty) characteristic to the protein fraction. The protein extracted via SAG also exhibited good heat stability (139–214 °C), rendering them potentially suitable for baking applications. Additionally, coupling Na₂CO₃ with liquid assisted grinding not only removed the need for organic solvents and conventional heating but also reduced solvent consumption by 83%, compared with the typical alkaline extraction, thus simplifying the downstream processes necessary to produce food fractions. This study demonstrates the potential significance of mechanochemical extraction processes in unlocking nutrients from unconventional resources like grass, to produce the next generation of sustainable food ingredients.

Lithium-ion batteries (LIBs) stand as the dominant power source for electric vehicles owing to their mature technology and exceptional performance. Consequently, metallic components of LIB cathode materials (Ni, Co, Li, and Mn) are assuming strategic significance. The imperative recycling of these metals has necessitated the development of novel technologies that can curtail secondary pollution arising from prevailing hydrometallurgical procedures, including issues such as wastewater generation and excessive energy and chemical consumption. In this study, we present an optimised mechanochemical process tailored for the magnetic recovery of cobalt from LiCoO₂, which is a crucial component of LIBs. Our methodology involves the initial reduction of cobalt, facilitated by aluminium, followed by a selective extraction process that leverages the magnetic properties of the obtained species. A systematic exploration of milling parameters was undertaken to comprehensively understand their influence on chemical reactions and to improve reduction efficiency. This research represents a significant stride towards fostering sustainable practices in the realm of LIB cathode material recycling, addressing critical concerns related to resource management and environmental impact.

This work provides an overview of sixteen different polymers potentially applicable as vessel materials in mechanochemical reactions, facilitating the selection of the optimal material tailored to each system individually. The investigation focused on the chemical resistances, especially under simultaneous mechanical stress, and the long-term stability of the utilized polymers. To assess these aspects, two reference reactions were employed: the direct mechanocatalytic Suzuki coupling of iodobenzene and phenylboronic acid, and the acid-catalysed acetalization reaction of ethylene glycol and 3-nitrobenzaldehyde. The palladium abrasion of the precious milling ball material used in the Suzuki reaction was examined through ICP-OES measurements for the polymers studied. Additionally, the temperature resistance of the polymers was discussed, along with their aptitude for in situ monitoring.

We demonstrate here the mechanochemical cocrystallization of trans-aconitic acid (TACA) with nicotinamide (NA) that leads to the formation of multi-component crystal forms with stoichiometric diversity, polymorphism with high Z′′ and the simultaneous existence of salt and cocrystal. During cocrystallization, we obtained a 1 : 1 molecular salt hydrate of TACA with NA and two polymorphic cocrystal hydrates of the same in 1 : 2 ratios, with a Z′′ value of seven, respectively. Manual grinding shows that 1 : 1 molecular salt and 1 : 2 cocrystal polymorphs are interconvertible under appropriate conditions. Moreover, cocrystal dissociation was observed upon heating the 1 : 2 cocrystal and in the presence of excess TACA during the preparation of the form I cocrystal using LAG. Thermal analysis, powder XRD, and DFT calculations establish the relative stability of the multi-component solids. Three-component polymorphic systems with high Z′′ are quite unusual; however, based on mechanochemistry, we have successfully synthesized and characterized them.

Pitavastatin (PTV), a potent cholesterol-lowering agent, holds considerable commercial appeal, driving chemists to fervently pursue its efficient and sustainable synthesis. Despite prolonged efforts over several decades, the quest for a simplified, more efficacious, and environmentally conscious manufacturing process for PTV remains a significant challenge. Our study introduces a three-step total mechano-synthesis, commencing with readily available 4-bromoquinoline, to produce the key intermediate (2-cyclopropyl-4-(4-fluorophenyl)quinoline-3-acrylaldehyde) of PTV. This methodology incorporates an extrusive Suzuki–Miyaura coupling, mechanochemical Minisci C–H alkylation, and extrusive oxidation Heck coupling, each thoroughly presented to display their scalability. Notably, we emphasize the extensive exploration of substrate versatility in Minisci reactions to access cyclopropane-bearing pharmaceutical compounds and natural products. This total mechano-synthesis route distinguishes itself through eco-friendly reaction conditions, exceptional stepwise efficiency, intuitive operability, and pronounced potential for large-scale implementation, paving the way for PTV's streamlined and sustainable manufacture.

Tribochemical reactions, chemical processes that occur by frictional shear at sliding interfaces, lead to tribofilm formation or substrate wear that directly affect the efficiency of machinery. Here, we report tribofilm growth through tribopolymerization and tribochemical wear of a silica surface due to reactions with organic precursors methylcyclopentane, cyclohexane, cyclohexene, and α-pinene. The activation volume determined from the stress dependence of reaction yield is correlated to the chemical reactivity of the precursor molecules. The molecules with higher tribochemical reactivity exhibited smaller activation volume, implying that less mechanical energy was required to initiate tribochemical reactions. Nudged elastic band calculations for the hypothetical pathways for the observed tribochemical reactions suggested that the smaller activation volume could be related to smaller thermal activation energy at the rate-limiting step. The tribofilm formation yield was found to increase with load whereas the load dependence of tribochemical wear was negligible. The environment dependence of the sliding processes was also analyzed. Results showed that, compared to a dry N₂ environment, the tribopolymerization reaction yield increased in dry air but decreased in N₂ with 40% relative humidity, while the wear rate remained unchanged. This finding suggested that during sliding, the reactive sites exposed at the worn surface could be re-oxidized by even trace amounts of oxygen or water vapor in the environment. This analysis of tribofilm yield and substrate wear in various environments showed that ambient gas can change the tribochemical reactivities of the reactant, which leads to different load dependencies of tribopolymerization and tribochemical wear.