Search Results (67)

Polysilicon is widely used in the photovoltaic and semiconductor industries. The presence of trace phosphorus impurities in the trichlorosilane feedstock can severely degrade the quality of polysilicon products. To address the urgent need for complete phosphorus removal of trichlorosilane, in this work, on the basis of the reducing ability of PCl₃ and the stronger Lewis base properties of its oxidation product, POCl₃, we developed an efficient material, xMo/Al₂O₃[y], using Al₂O₃ as the support and Mo species as active substances through a simple and straightforward method. Under the optimized preparation conditions of 7.8% Mo loading and a calcination temperature of 450 °C, the adsorbent exhibited optimal performance in an organic system simulating a trichlorosilane system with a P adsorption capacity of 53.52 mg g⁻¹, achieving near-complete elimination of phosphorus impurities. A series of characterization analyses suggested the following primary removal mechanism: initial oxidation of PCl₃ to POCl₃ by Mo⁶⁺ species, followed by its complexation with Mo sites via Lewis acid-base interactions. Furthermore, surface morphology damage during the removal process and the accumulation of reaction products on the spent adsorbent are the main factors contributing to its deactivation. This work presents an effective strategy for the deep dephosphorization of trichlorosilane. Full article

Near-critical and supercritical carbon dioxide (SC-CO₂) is extensively utilized in high-pressure separation, extraction, polymer processing, and carbon capture and utilization (CCU) technologies owing to its tunable density, low viscosity, high diffusivity, and environmentally benign nature. Reliable phase equilibrium data are indispensable for process design and optimization, especially in the near-critical region characterized by pronounced non-idealities, high compressibility, and density fluctuations. This review synthesizes experimental phase behaviour studies for binary mixtures of CO₂ with diverse components, including hydrocarbons, alcohols, ethers, esters, ketones, water, monomers/polymers, ionic liquids (ILs), and deep eutectic solvents (DESs), compiling extensive vapour–liquid equilibrium (VLE), liquid–liquid equilibrium (LLE), and critical data across industrially relevant pressure (up to 40 MPa) and temperature (up to 400 K) ranges. It critically evaluates analytical (sampling and non-sampling) and synthetic methodologies, addressing challenges in CO₂-rich phase handling, depressurization artefacts, and near-critical phenomena, while assessing data consistency against established reliability criteria. Key trends emerge, such as enhanced solubility with increasing pressure and CO₂ density, chain-length dependencies in hydrocarbons and alcohols, and Lewis acid–base interactions driving solvation in polar systems. The review highlights gaps in multicomponent data and proposes integrating high-quality experiments with advanced thermodynamic modelling to enhance predictive accuracy. Future directions emphasize high-precision in situ techniques, expanded datasets for complex mixtures, and novel CO₂-philic solvents to advance sustainable SC-CO₂ applications. Full article

Metallic biomaterials play essential roles in modern medical devices, but their long-term performance depends critically on protein adsorption and subsequent cellular responses at material interfaces. This review examines the molecular mechanisms governing these interactions and discusses surface modification strategies for controlling biocompatibility. The physicochemical properties of oxide layers formed on metal surfaces—including Lewis acid-base chemistry, surface charge, surface free energy, and permittivity—collectively determine protein adsorption behavior. Titanium surfaces promote stable protein adsorption through strong coordination bonds with carboxylate groups, while stainless steel surfaces show complex formation with proteins that can lead to metal ion release. Surface modification strategies can be systematically categorized based on two key parameters: effective ligand density (σ_eff) and effective mechanical response (E_eff). Direct control approaches include protein immobilization, self-assembled monolayers, and ionic modifications. The most promising strategies involve coupled control of both parameters through hierarchical surface architectures and three-dimensional modifications. Despite advances in understanding molecular-level interactions, substantial challenges remain in bridging the gap between surface chemistry and tissue-level biological performance. Future developments must address three-dimensional interfacial interactions and develop systems-level approaches integrating multiple scales of biological organization to enable rational design of next-generation metallic biomaterials. Full article

Polyethylene terephthalate (PET) is widely used, yet the accumulation of its waste poses serious environmental challenges, making efficient recycling essential. PET glycolysis using EG as a solvent has emerged as a green recycling strategy. In this study, a cyclic alkylamino carbene copper (CAAC-Cu) complex was prepared as a catalyst for PET glycolysis. Under optimized conditions (160 °C, 90 min, catalyst amount 3 wt%, and PET/EG = 1:4.), PET conversion reached 98.2%, the selectivity toward BHET was 88.1%, and the yield was 86.5%. Kinetic analysis indicated that the glycolysis follows first-order kinetics with an activation energy of 98.7 kJ mol⁻¹. In addition, the catalyst can be recovered together with excess EG, and after multiple recycles, PET degradation remained above 95% and BHET yield remained above 80%. A possible mechanism has also been proposed: Cu acts as a Lewis acid coordinating to the carbonyl oxygen of PET, facilitating ester bond activation, while the amino-carbene forms hydrogen bonds with EG, assisting bond cleavage in a Brønsted-base manner. This catalytic system provides a novel and efficient approach for the green, high-performance glycolysis of PET. Full article

The 1:1 stoichiometric reactions of α-amino isobutyric acid (H₂Aib) and diaminosilanes of the type SiRR′(NR¹R²)₂ (SiMe₂(imidazol-1-yl)₂, SiMe₂(NHnPr)₂, and SiRR′(pyrrolidin-1-yl)₂ with R,R′ = Me,Me, Me,H, Me,Vi, and Et,Et) afforded the pentacoordinate silicon complexes (Aib)SiRR′(HNR¹R²) with the release of one equivalent of HNR¹R². Single-crystal X-ray diffraction analyses confirmed the coordination of the N-donor Lewis base (i.e., imidazole, n-propylamine, and pyrrolidine, respectively) in an axial position of the distorted trigonal-bipyramidal Si-coordination sphere, trans to the carboxylate O atom of the Si-chelating Aib-dianion. The N–H moieties of the adduct-forming Lewis bases are involved in N–H⋯O hydrogen bonds with carboxylate groups of adjacent complex molecules, thus supporting the supramolecular structures of these adducts. The equatorially bound NH group of the Aib-dianion is involved in N–H⋯O hydrogen bonds in most cases, and it gives rise to residual dipolar coupling of the ¹⁴N nucleus with its directly bound atoms C and Si, thus causing characteristic shapes of both the ²⁹Si and ¹³C NMR signals of these two atoms in the solid-state spectra. In contrast to the adduct-formation reactions, the analogous conversion of H₂Aib and SiMe₂(NHtBu)₂ did not afford an amine adduct. Instead, a second equivalent of H₂Aib entered the reaction, and the ionic silicon complex [tBuNH₃]⁺[(Aib)₂SiMe]⁻ was obtained and characterized by crystallography and solution NMR spectroscopy. Full article

Titanium, the second most abundant and one of the cheapest, non-toxic transition metals in the Earth’s crust, is highly favorable for catalytic applications due to its widespread availability, low cost, low toxicity, and well-documented biocompatibility. However, because of its high affinity for oxygen and inherent Lewis acidity, titanium complexes generally exhibit lower tolerance toward various functional groups compared with complexes of later transition metals. The incorporation of cyclopentadienyl ligands significantly enhances the structural tunability of these complexes in their 3D configuration. By modifying the ligand framework, it is possible to fine-tune the Lewis acidity of the central titanium atom as well as the lability and binding characteristics of the ligands. This strategy enables precise control over the catalytic performance of titanocene complexes. The main body of this review provides an overview of recent advances in titanocene catalysis within the field of chemical synthesis since 2019. It includes illustrative examples that demonstrate the substrate scope and practical applications of titanocene catalysts in the synthesis of complex organic molecules and natural products. Finally, the review outlines current research opportunities and strategic directions for future developments in titanocene-based catalysis. Full article

The main categories of transition metal–mercury heterometallic compounds are briefly summarized. The attention is focused on complexes and clusters where the {Hg-Y} fragment, where Y represents a halide atom, interacts with transition metals. Most of the structurally characterized derivatives are organometallic compounds where the transition metals belong to the Groups 6, 8, 9 and 10. More than one {Hg-Y} group can be present in the same compound, interacting with the same or with different transition metals. The main synthetic strategies are discussed, and structural data of representative compounds are reported. According to the isolobality with hydrogen, {Hg-Y} can form from one to three M-{Hg-Y} bonds, but further interactions can be present, such as mercurophilic and Hg···halide contacts. The formal oxidation state of mercury is sometimes ambiguous and thus {Hg-Y} can be considered as a Lewis acid or base on varying the transition metal fragment. Density functional theory calculations on selected Group 6 and Group 9 model compounds are provided in order to shed light on this aspect. Full article

The discriminative detection of volatile primary aliphatic diamines (VPADs) is a relevant and timely issue. This paper explores the distinctive optical features of H-type and J-type aggregates on paper-based (PB) films, namely H-PB and J-PB films, respectively, of a Lewis acidic Zn(salen)-type complex upon chemisorption of vapors of ditopic VPADs versus those of monotopic volatile amines. While volatile monotopic Lewis bases upon chemisorption give rise to mono-adducts accompanied by enhancement of the fluorescence, in contrast, VPADs act as ditopic bases forming di-adducts with distinct optical properties, leading to fluorescence quenching. This behavior enables the sensitive and discriminative detection of VPAD vapors from those of volatile monoamines. For example, for ethylenediamine (EDA), using J-PB films, sensitive detection is achieved with a LOD down to 6.6 ppm, lower than the OSHA permissible exposure limit of 10 ppm for EDA, and a linear dynamic range up to 100 ppm. Instead, H-PB films enable the detection of EDA vapors at higher ppm concentrations (up to 3000 ppm) with a linearity of up to 1000 ppm. Thus, the combination of both H-PB and J-PB films of the Zn(salen)-type complex represents a unique example of the sensitive and discriminative detection of EDA vapors in such a wide concentration range. Full article

Unique structural and chemical properties, such as ion exchange, developed inner surface, etc., as well as the wide possibilities and flexibility of regulating these properties, cause a keen interest in zeolites. They are widely used in industry as molecular sieves, ion exchangers and catalysts. Current trends in the development of zeolite-based catalysts include the adaptation of their cationic composition, acidity and porosity for a specific catalytic process. Recent studies have shown that mesoporosity is beneficial to the rational design of catalysts with controlled product selectivity and an improved catalyst lifetime due to its efficient mass-transport properties. Nuclear magnetic resonance (NMR) has proven to be a reliable method for studying zeolites. Solid-state NMR spectroscopy allows for the quantification of both Lewis and Brønsted acidity in zeolite catalysts and, nowadays, ²⁷Al and ²⁹Si magic angle spinning NMR spectroscopy has become firmly established in the set of approved methods for characterizing zeolites. The use of probe molecules opens up the possibility for the indirect measurement of the characteristics of acid sites. NMR relaxation is less common, although it is especially informative and enlightening for studying the mobility of guest molecules in the porous matrix. Moreover, the NMR relaxation of guest molecules and NMR cryoporometry can quantify pore size distribution on a broader scale (compared to traditional methods), which is especially important for systems with complex pore organization. Over the last few years, there has been a growing interest in the use of 2D NMR relaxation techniques to probe porous catalysts, such as 2D $T_1$–$T_2$ correlation to study the acidity of the surface of catalysts and 2D $T_2$–$T_2$ exchange to study pore connectivity. This contribution provides a comprehensive review of various NMR relaxation techniques for studying porous media and recent results of their applications in probing micro- and mesoporous zeolites, mainly focused on the mobility of adsorbed molecules, the acidity of the zeolite surface and the pore size distribution and connectivity of zeolites with hierarchical porosity. Full article

Iodosilarene derivatives (PhIO, PhI(OAc)₂) constitute an important class of oxygen atom transfer reagents in organic synthesis and are often used together with iron-based catalysts. Since the factors controlling the ability of iron centers to catalyze alkane hydroxylation are not yet fully understood, the aim of this report is to develop bioinspired non-heme iron catalysts in combination with PhI(OAc)₂, which are suitable for performing C-H activation. Overall, this study provides insight into the iron-based ([Fe^II(PBI)₃(CF₃SO₃)₂] (1), where PBI = 2-(2-pyridyl)benzimidazole) catalytic and stoichiometric hydroxylation of triphenylmethane using PhI(OAc)₂, highlighting the importance of reaction conditions including the effect of the co-ligands (para-substituted pyridines) and oxidants (para-substituted iodosylbenzene diacetates) on product yields and reaction kinetics. A number of mechanistic studies have been carried out on the mechanism of triphenylmethane hydroxylation, including C-H activation, supporting the reactive intermediate, and investigating the effects of equatorial co-ligands and coordinated oxidants. Strong evidence for the electrophilic nature of the reaction was observed based on competitive experiments, which included a Hammett correlation between the relative reaction rate (logk_rel) and the σ_p (4R-Py and 4R’-PhI(OAc)₂) parameters in both stoichiometric (ρ = +0.87 and +0.92) and catalytic (ρ = +0.97 and +0.77) reactions. The presence of [(PBI)₂(4R-Py)Fe^IIIOIPh-4R’]³⁺ intermediates, as well as the effect of co-ligands and coordinated oxidants, was supported by their spectral (UV–visible) and redox properties. It has been proven that the electrophilic nature of iron(III)-iodozilarene complexes is crucial in the oxidation reaction of triphenylmethane. The hydroxylation rates showed a linear correlation with the Fe^III/Fe^II redox potentials (in the range of −350 mV and −524 mV), which suggests that the Lewis acidity and redox properties of the metal centers greatly influence the reactivity of the reactive intermediates. Full article

In recent years, dibenzyl disulfide (DBDS) in transformer oils has caused many transformer failures around the world, and its removal has attracted more attention. In this work, nine imidazolium-based ionic liquids (ILs) were applied as effective, green desulfurization extractants for DBDS-containing transformer oil for the first time. The results show that the desulfurization ability of the ILs for DBDS followed the order of [BMIM]FeCl₄ > [BMIM]N(CN)₂ > [BMIM]SCN > [BMIM](C₄H₉O)₂PO₂ > [BMIM]MeSO₄ > [BMIM]NTf₂ > [BMIM]OTf > [BMIM]PF₆ > [BMIM]BF₄. Especially, [BMIM]FeCl₄ ionic liquid had excellent removal efficiency for DBDS, with its S partition coefficient K_N (S) being up to 2642, which was much higher than the other eight imidazolium-based ILs. Moreover, the extractive performance of [BMIM]FeCl₄ increased with an increasing molar ratio of FeCl₃ to [BMIM]Cl, which was attributed to its Lewis acidity and fluidity. [BMIM]FeCl₄ ionic liquid could also avail in the desulfurization of diphenyl sulfide (DPS) from model oils. The experimental results demonstrate that π−π action, π-complexation, and Lewis acid−base interaction played important roles in the desulfurization process. Finally, the ([BMIM]FeCl₄) ionic liquid could be recycled five times without a significant decrease in extractive ability. Full article

Facile and sensitive methods for detecting neonicotinoids (NEOs) in aquatic environments are crucial because they are found in extremely low concentrations in complex matrices. Herein, nitrogen-based magnetic conjugated microporous polymers (Fe₃O₄@N-CMP) with quaternary ammonium groups were synthesized for efficient magnetic solid-phase extraction (MSPE) of NEOs from tap water, rainwater, and lake water. Fe₃O₄@N-CMP possessed a suitable specific surface area, extended π-conjugated system, and numerous cationic groups. These properties endow Fe₃O₄@N-CMP with superior extraction efficiency toward NEOs. The excellent adsorption capacity of Fe₃O₄@N-CMP toward NEOs was attributed to its π–π stacking, Lewis acid–base, and electrostatic interactions. The proposed MSPE-HPLC-DAD approach based on Fe₃O₄@N-CMP exhibited a wide linear range (0.1–200 µg/L), low detection limits (0.3–0.5 µg/L), satisfactory precision, and acceptable reproducibility under optimal conditions. In addition, the established method was effectively utilized for the analysis of NEOs in tap water, rainwater, and lake water. Excellent recoveries of NEOs at three spiked levels were in the range of 70.4 to 122.7%, with RSDs less than 10%. This study provides a reliable pretreatment method for monitoring NEOs in environmental water samples. Full article

Laser ablated Be atoms have been reacted with acetonitrile molecules in 4 K solid neon matrix. The diberyllium products BeBeNCCH₃ and CNBeBeCH₃ have been identified by D and ¹³C isotopic substitutions and quantum chemical calculations. The stabilization of the diberyllium species is rationalized from the formation of the real Be−Be single bonds with bond distances as 2.077 and 2.058 Å and binding energies as −27.1 and −77.2 kcal/mol calculated at CCSD (T)/aug-cc-pVTZ level of theory for BeBeNCCH₃ and CNBeBeCH₃, respectively. EDA-NOCV analysis described the interaction between Be₂ and NC···CH₃ fragments as Lewis “acid−base” interactions. In the complexes, the Be₂ moiety carries positive charges which transfer from antibonding orbital of Be₂ to the bonding fragments significantly strengthen the Be−Be bonds that are corroborated by AIM, LOL and NBO analyses. In addition, mono beryllium products BeNCCH₃, CNBeCH₃, HBeCH₂CN and HBeNCCH₂ have also been observed in our experiments. Full article

In chloroform solution, the reaction of bis(tert-butylamino)dimethylsilane ((tBuNH)₂SiMe₂) and an α-amino acid (α-amino isobutyric acid, H₂Aib; D-phenylglycine, H₂Phg; L-valine, H₂Val) in the presence of N-methylimidazole (NMI) gave rise to the formation of the pentacoordinate silicon complexes (Aib)SiMe₂-NMI, (Phg)SiMe₂-NMI and (Val)SiMe₂-NMI, respectively. Therein, the amino acid building block was a di-anionic bidentate chelator at the silicon atom. In solution, the complexes were involved in rapid coordination–dissociation equilibria between the pentacoordinate Si complex (e.g., (Aib)SiMe₂-NMI) and its constituents NMI and a five-membered silaheterocycle (e.g., (Aib)SiMe₂), as shown by ²⁹Si NMR spectroscopy. The energetics of the Lewis acid-base adduct formation and the competing solvation of the NMI molecule by chloroform were assessed with the aid of computational methods. In CDCl₃ solution, deuteration of the silaheterocycle NH group proceeded rapidly, with more than 50% conversion within two days. Upon cooling to −44 °C, the chloroform solvates of the adducts (Aib)SiMe₂-NMI and (Phg)SiMe₂-NMI crystallized from their parent solutions and allowed for their single-crystal X-ray diffraction analyses. In both cases, the Si atom was situated in a distorted trigonal bipyramidal coordination sphere with equatorial Si–C bonds and an equatorial Si–N bond (the one of the silaheterocycle). The axial positions were occupied by a carboxylate O atom of the silaheterocycle and the NMI ligand’s donor-N-atom. Full article

Tetravalent Sn species, such as zeolite or oxide, possess Lewis acidic properties, and thus exhibit prominent catalytic performance in several reactions when they are incorporated into the silica framework. Unfortunately, the synthesis of Sn-based zeolite (Sn–Beta) usually suffers from several drawbacks, including a long crystallization time, limited framework Sn content and complex synthesis steps. Sn-based composite oxides are favored in the industry, due to their simple synthesis steps and easy control of their pore structure, morphology and Sn content. In this work, an aerosol-assisted method is used to prepare Sn–Si composite oxide microspheres, using CTAB as template. The method is based on the formation of aerosol from a solution of Sn, Si precursors and a template (CTAB). The introduction of CTAB causes the surface tension of the atomized droplets to decrease. During the fast drying of the droplets, the Sn–Si composite oxide microspheres with a concave hollow morphology were first formed. After calcination, calibrated mesopores of 2.3 nm were also formed, with a specific surface area of 1260 m²/g and a mesopores ratio of 0.84. Sn species are incorporated in the silica network, mainly in the form of single sites. The resulting material proved to exhibit high catalytic performances in the Baeyer–Villiger oxidation of 2-adamantanone by using H₂O₂ as green oxidant, which was mainly attributed to the enhancement of the access to the catalytic tin sites through both the continuous hollow and mesopore channels, which have a 52% conversion of 2-adamantanone after 3 h of reaction. This method is simple, convenient, cheap and can be continuously produced, meaning it has broad potential for industrial application. Full article