Model Reaction Research Articles

Preparation of highly dispersed Pt catalyst by CeOx 'islands' modification of dendritic mesoporous SiO2: CO as a probe molecule

There are still challenges in producing noble metal catalysts with atomic dispersion on a large scale in current. This study presents a method for preparing a highly dispersed Pt catalyst (Pt/CeOx/DMS) by modifying dendritic mesoporous SiO2 (DMS) with CeOx 'islands'. The results demonstrate that Pt is highly dispersed on the CeOx/DMS carrier, with the majority of Pt existing in the form of single atoms (Pt/20 wt.% CeOx/DMS). The dendritic DMS has a large specific area (451 m2 g−1) that provides more sites for the formation of CeOx 'islands'. This promotes the dispersion of Pt, significantly improving the oxidation activity of CO. The addition of CeOx 'islands' to the Pt/DMS catalyst promotes the desorption of CO on Pt NPs, enhances the adsorption and activation of O2, and further improves the activity of catalyst. This is because of the synergistic effect between Pt and CeOx 'islands'. The DFT result found that it is more beneficial for Pt1 to adsorb O2 before other reactions. To test the activity and stability of the catalyst, the team conducted catalytic oxidation of CO as a model reaction. The results show that the promotion of CeOx 'island' reduces T90 of CO catalytic oxidation by 16 ℃. In the high-temperature stability test of the catalyst, it was observed that even after reacting at 500 ℃ for 8 h, the catalyst can still achieve 90 % conversion of CO at 147 ℃, demonstrating its good stability. This study provides a foundation for designing a new type of CO oxidation catalyst. The catalyst features high dispersion Pt and exhibits excellent catalytic activity.

Unlocking the potential of Opuntia species mucilage in chemistry

Herein, we describe a detailed protocol to extract the mucilage from different species of the genus Opuntia spp. (i.e., Opuntia Ficus (OFi), Opuntia Dillenii (ODi) and Opuntia Robusta (ORo)). The extracted mucilage was characterized by NMR, FTIR-ATR, HPLC, and TGA. OFi was found to have the highest phenolic content, 7.84 ± 1.93 mg catechol/g mucilage. The mucilage from the three species were characterized by having a high content of monosaccharides, being mannose and glucose the most abundant components (ca. 48–73 % and 23–35 %, respectively). In the context of biomass revalorization, the mucilage was proven to serve as a reducing and stabilizing agent in the synthesis of gold nanoparticles (AuNP/mucilage). The synthesis was optimized with a mucilage concentration of 2 mg/mL using 12.5 μL of KAuCl4 and was carried out at 80 °C for 90 min. This protocol afforded spherical nanoparticles with an average size of 9.7 ± 4.0 nm that were stable for at least 14 days, as demonstrated by TEM. Synthesized AuNP/mucilage was evaluated as a plasmonic catalyst for the reduction of 4-nitrophenol as model reaction, showing a considerable enhancement in its kapp of 97 % under white light and a decrease of 24.8 % in its activation energy.

The interaction between lipid oxidation and the Maillard reaction model of lysine-glucose on aroma formation in fragrant sesame oil

The formation mechanism behind the sophisticated aromas of sesame oil (SO) has not been elucidated. The interaction effects of the Maillard reaction (MR) and lipid oxidation on the aroma formation of fragrant sesame oil were investigated in model reaction systems made of l-lysine (Lys) and d-glucose (Glc) with or without fresh SO (FSO) or oxidized SO (OSO). The addition of OSO to the Lys-Glc model increased the MR browning at 294 nm and 420 nm and enhanced the DPPH radical scavenging activity greater than the addition of FSO (p < 0.05). The presence of lysine and glucose inhibited the oxidation of sesame oil, reduced the loss of γ-tocopherol, and facilitated the formation of sesamol (p < 0.05). The Maillard-lipid interaction led to the increased concentrations of some of the alkylpyrazines, alkylfurans, and MR-derived ketones and acids (p < 0.05) while reducing the concentrations of other pyrazines, lipid-derived furans, aliphatic aldehydes, ketones, alcohols, and acids (p < 0.05). The addition of FSO to the MR model enhanced the characteristic roasted, nutty, sweet, and fatty aromas in sesame oil (p < 0.05), while excessive lipid oxidation (OSO) brought about an unpleasant oxidized odor and reduced the characteristic aromas. This study helps to understand the sophisticated aroma formation mechanism in sesame oil and provides scientific instruction for precise flavor control in the production of sesame oil.

The Synthesis of 2'-Hydroxychalcones under Ball Mill Conditions and Their Biological Activities.

Chalcones are polyphenols that belong to the flavonoids family, known for their broad pharmacological properties. They have thus attracted the attention of chemists for their obtention and potential activities. In our study, a library of compounds from 2'-hydroxychalcone's family was first synthesized. A one-step mechanochemical synthesis via Claisen-Schmidt condensation reaction under ball mill conditions was studied, first in a model reaction between a 5'-fluoro-2'-hydroxyacetophenone and 3,4-dimethoxybenzaldehyde. The reaction was optimized in terms of catalysts, ratio of reagents, reaction time, and influence of additives. Among all assays, we retained the best one, which gave the highest yield of 96% when operating in the presence of 1 + 1 eq. of substituted benzaldehyde and 2 eq. of KOH under two grinding cycles of 30 min. Thus, this protocol was adopted for the synthesis of the selected library of 2'-hydroxychalcones derivatives. The biological activities of 17 compounds were then assessed against Plasmodium falciparum, Leishmania donovani parasite development, as well as IGR-39 melanoma cell lines by inhibiting their viability and proliferation. Compounds 6 and 11 are the most potent against L. donovani, exhibiting IC50 values of 2.33 µM and 2.82 µM, respectively, better than the reference drug Miltefosine (3.66 µM). Compound 15 presented the most interesting antimalarial activity against the 3D7 strain, with IC50 = 3.21 µM. Finally, chalcone 12 gave the best result against IGR-39 melanoma cell lines, with an IC50 value of 12 µM better than the reference drug Dacarbazine (IC50 = 25 µM).

HLM chip – A microfluidic approach to study the mechanistic basis of cytochrome P450 inhibition using immobilized human liver microsomes

Cytochrome P450 (CYP) system is a critical elimination route to most pharmaceuticals in human, but also prone to drug-drug interactions arising from the fact that concomitantly administered pharmaceuticals inhibit one another's CYP metabolism. The most severe form of CYP interactions is irreversible inhibition, which results in permanent inactivation of the critical CYP pathway and is only restored by de novo synthesis of new functional enzymes. In this study, we conceptualize a microfluidic approach to mechanistic CYP inhibition studies using human liver microsomes (HLMs) immobilized onto the walls of a polymer micropillar array. We evaluated the feasibility of these HLM chips for CYP inhibition studies by establishing the stability and the enzyme kinetics for a CYP2C9 model reaction under microfluidic flow and determining the half-maximal inhibitory concentrations (IC50) of three human CYP2C9 inhibitors (sulfaphenazole, tienilic acid, miconazole), including evaluation of their inhibition mechanisms and nonspecific microsomal binding on chip. Overall, the enzyme kinetics of CYP2C9 metabolism on the HLM chip (KM = 127 ± 55 µM) was shown to be similar to that of static HLM incubations (KM = 114 ± 14 µM) and the IC50 values toward CYP2C9 derived from the microfluidic assays (sulfaphenazole 0.38 ± 0.09 µM, tienilic acid 3.4 ± 0.6 µM, miconazole 0.54 ± 0.09 µM) correlated well with those determined using current standard IC50 shift assays. Most importantly, the HLM chip could distinguish between reversible (sulfaphenazole) and irreversible (tienilic acid) enzyme inhibitors in a single, automated experiment, indicating the great potential of the HLM chip to simplify current workflows used in mechanistic CYP inhibition studies. Furthermore, the results suggest that the HLM chip can also identify irreversible enzyme inhibitors, which are not necessarily resulting in a time-dependent inhibition (like suicide inhibitors), but whose inhibition mechanism is based on other kind of covalent or irreversible interaction with the CYP system. With our HLM chip approach, we could identify miconazole as such a compound that nonselectively inhibits the human CYP system with a prolonged, possibly irreversible impact in vitro, even if it is not a time-dependent inhibitor according to the IC50 shift assay.

Synthesis of PEI Grafted Poly (Ionic Liquid)s: Optimization and Kinetics Modeling of Effective CO2 Fixation Reactions

AbstractFixing the greenhouse gas CO2 through epoxide helps to mitigate worldwide ecological troubles. The applications of metal‐free and solvent‐free catalysts remain a challenge for CO2 catalytic conversion. In this work, an array of quaternary ammonium salts derived from polyethyleneimine with hydroxyl groups ([PEI‐GDMAB‐Cn]Br) were constructed by the reaction of branched PEI with a molecular weight of 10000 and glycidyl alkyl dimethylammonium bromide. A range of experiments were designed to demonstrate that [PEI‐GDMAB‐Cn]Br can be considered as a valid metal‐free and solvent‐free homogeneous catalyst for the CO2‐epoxide cycloaddition reaction. Among of [PEI‐GDMAB‐Cn]Br, [PEI‐GDMAB‐C18]Br catalyzed the model reaction of CO2 and epichlorohydrin under optimized reaction conditions (T=80 °C, 1.0 atm CO2, catalyst 1 mol%, ECH 15 mmol, 16 h) and the conversion achieved at 97.5 %. Moreover, the catalyst exhibited stable reusability and broad substrate applicability, which was used in the following cycle succinctly, because of self‐separated properties by temperature control. The [PEI‐GDMAB‐C18]Br catalyzed reaction process was detected as a pseudo‐first‐order reaction after kinetic studies and an Ea was calculated to be 50.65 kJ/mol. A combinatorial catalytic mechanism of hydrogen bonding and bromide ions is suggested to explain the remarkable catalytic performance of this bifunctional catalyst.

CuPd bimetallic nanoparticles supported magnetic ionic liquid-derived N-doped carbon as a highly efficient heterogeneous catalyst for the one-pot oxidative multicomponent reactions

BackgroundMulticomponent reactions often rely on aldehydes as the reactants, limiting their widespread use. To enhance the versatility and scope of these reactions, aldehydes can be replaced with alcohols. MethodsIn this study, nitrogen-doped magnetic carbon nanostructures modified with imidazolium-based ionic liquid (Fe3O4@NC-IL) were prepared. These nanostructures were synthesized by a one-pot hydrothermal carbonization method using ferric chloride in the presence of glucose, urea, epichlorohydrin and 1-methylimidazole as carbon source, nitrogen source, linker and ionic liquid, respectively. Then, CuPd bimetallic nanoparticles were immobilized on the synthesized nanostructures by a wet chemical reduction process. Significant findingsThe catalytic activity of the nanostructures was evaluated in the oxidation of alcohol under base-free conditions. The results indicate that the CuPd bimetallic catalyst exhibited better catalytic performance than both Cu and Pd monometallic catalysts, suggesting a synergistic effect between copper and palladium. Also, a non-ionic liquid-based catalyst was synthesized and used in the model reaction to study the effect of imidazolium ionic liquid species on the catalytic activity. The results showed that these species enhanced the catalytic activity. Finally, the catalytic activity of the synthesized structure was evaluated through a one-pot tandem oxidative synthesis of dihydropyrimidinones (Biginelli reaction) and dihydropyridines (Hantzsch reaction).

Diphenyl Carbonate: Recent Progress on Its Catalytic Synthesis by Transesterification

Diphenyl carbonate is one of the raw materials used for the synthesis of polycarbonate, and its green and clean production is of great importance to the non-phosgene process for polycarbonate. The production of diphenyl carbonate by transesterification is its representative process route and is considered to be one of the typical examples of a green and sustainable process for chemicals. Since the discovery of the transesterification catalyst for diphenyl carbonate in the 1970s, researchers have been committed to improving its catalytic activity and selectivity and, correspondingly, the reaction engineering process. However, thermodynamic limitations, low activity, low selectivity, and limited stability have been bottlenecks that the transesterification catalyst has not been able to completely overcome, and the improvement of the catalyst is still ongoing. Therefore, this review takes the transesterification reaction of dimethyl carbonate and phenol as a model reaction and, based on a review of the progress in catalyst research on catalytic reaction processes, tries to clarify the structure–activity relationship between catalytic active sites and catalytic performance in homogeneous and heterogeneous catalytic processes and provides an overview of the progress in catalyst synthesis and modification.

Viscous dissipation and Joule heating effects of Carreau nanofluid axisymmetric flow past unsteady radially stretching porous disk

In this piece of communication, a theoretical investigation of two dimensional boundary layer flow of Magnetohydrodynamics (MHD) Carreau nanofluid axisymmetric flow past unsteady radially stretching porous disk is made. The investigation includes the effects of viscous dissipation, Joule heating, thermal radiation, suction/injection, Darcy–Forchheimer porosity model and binary chemical reaction with activation energy, etc. To examine the impacts of the aforementioned effects, the conservation laws are formulated with strongly nonlinear partial differential equations (PDEs), which are then transformed into a system of initial value problems (IVPs) using appropriate similarity transformations and techniques. The 5th order Runge–Kutta with the shooting technique is used to find numerical solutions aided by Python programming with built in program “fsolve”. The method is validated with other published articles under common assumptions and it agrees nicely. The impacts of the pertinent parameters on velocity, temperature, concentration, skin friction coefficient and the rates of mass and heat transfers with in the flow regime are displayed using graphs and tables. The main outcomes include the motivation of local Nusselt and Sherwood numbers for shear thickening (n=1.5) than shear thinning (n=0.5) cases of the Carreau nanofluid. The momentum boundary layer of the Carreau nanofluid gets thinner with an increase in Forchheimer number, unsteady and suction parameters. A dual nature is observed for concentration of the Carreau nanofluid with a rise in Eckert number, i.e increasing in concentration around the wall and decreasing far away from the wall. The rise in destructive and constructive chemical reaction parameters disperse and accumulate the concentration of the system, respectively.

Study of Direct N7 Regioselective tert-Alkylation of 6-Substituted Purines and Their Modification at Position C6 through O, S, N, and C Substituents.

A new N7 direct regioselective method allowing the introduction of tert-alkyl groups into appropriate 6-substituted purine derivatives is developed. This method is based on a reaction of N-trimethylsilylated purines with a tert-alkyl halide using SnCl4 as a catalyst. In this work, we study the structure and optimal reaction conditions leading to the N7 isomer and in some cases also to the N9 isomer. The main goal is devoted to preparing 7-(tert-butyl)-6-chloropurine as a suitable compound for other purine transformations. The stability of the tert-butyl group at the N7 position is tested for classic model reactions, leading to the preparation of new 6,7-disubstituted purine derivatives, which is also interesting from the point of view of possible biological activity.

Glucometabolic-Related Genes as Diagnostic Biomarkers and Therapeutic Targets for Alzheimer's Disease and Type 2 Diabetes Mellitus: A Bioinformatics Analysis.

Alzheimer's disease (AD) and type 2 diabetes mellitus (T2DM) are two widespread chronic disorders characterized by shared risk factors and molecular pathways. Glucose metabolism, pivotal for cellular homeostasis and energy supply, plays a critical role in these diseases. Its disturbance has been linked to the pathogenesis of both AD and T2DM. However, a comprehensive investigation into the specific roles of glucometabolic genes in the onset and progression of AD and T2DM has yet to be conducted. By analyzing microarray datasets from the Gene Expression Omnibus (GEO) repository, we identified differentially expressed glucometabolic genes (DEGs) in AD and T2DM cohorts. A range of bioinformatics tools were employed for functional annotation, pathway enrichment, protein interaction network construction, module analysis, ROC curve assessment, correlation matrix construction, gene set enrichment analysis, and gene-drug interaction mapping of these DEGs. Key genes were further validated using quantitative real-time polymerase chain reaction (qRT-PCR) in AD and T2DM murine models. Our investigation identified 41 glucometabolic-related DEGs, with six prominent genes (G6PD, PKM, ENO3, PFKL, PGD, and TALDO1) being common in both AD and T2DM cohorts. These genes play crucial roles in metabolic pathways including glycolysis, pentose phosphate pathway, and amino sugar metabolism. Their diagnostic potential was highlighted by area under curve (AUC) values exceeding 0.6 for AD and 0.8 for T2DM. Further analysis explored the interactions, pathway enrichments, regulatory mechanisms, and potential drug interactions of these key genes. In the AD murine model, quantitative real-time polymerase chain reaction (qRT-PCR) analysis revealed significant upregulation of G6pd, Eno3, and Taldo1. Similarly, in the T2DM murine model, elevated expression levels of G6pd, Pfkl, Eno3, and Pgd were observed. Our rigorous research sheds light on the molecular interconnections between AD and T2DM from a glucometabolic perspective, revealing new opportunities for pharmacological innovation and therapeutic approaches. This study appears to be the first to extensively investigate glucometabolic-associated DEGs and key genes in both AD and T2DM, utilizing multiple datasets. These insights are set to enhance our understanding of the complex pathophysiology underlying these widespread chronic diseases.

Comparative Study on the H-Abstraction Reactions of Isopropyl Acetate and Propyl Acetate by HO2 and OH Radicals.

Isopropyl acetate (IPA) and propyl acetate (PA) are recognized as promising biofuels suitable for applications as fuel additives and biodiesel models. The H-abstraction reactions with radicals stand out as the fundamental initiating reactions in the combustion kinetic models for IPA and PA. In the present work, the kinetic calculations of IPA and PA plus HO2 and OH radicals were investigated at M06-2X/cc-pVTZ//G4, M08-HX/maug-cc-pVTZ, and CCSD(T)/jul-cc-pVTZ levels. The thermodynamic calculations were obtained based on the G4 and CBS-APNO methods. Rate coefficients were calculated using both transition state theory and canonical variational transition state theory with tunneling correction at the temperature range of 250-2000 K. The total rate constants for the IPA + OH system were fitted as follows: k = 0.4674 × T3.927 exp(2128/T) (cm3 mol-1 s-1), and for the PA + OH system, the total rate constants were determined using the following equation: k = 0.0161 × T4.373 exp(2220/T) (cm3 mol-1 s-1). The rate coefficients of IPA + OH reactions determined based on the M08-HX/maug-cc-pVTZ level effectively replicate the experimental data, while H-abstraction rate coefficients of PA + OH by the CCSD(T)/jul-cc-pVTZ method accurately reproduce the experimental data. Refining the H-abstraction rate coefficients in the kinetic mechanism of PA, as proposed by Dayma et al. [Proc. Combust. Inst. 37 (2019) 429-436], has been achieved through incorporating the present calculated data, leading to the development of a revised mechanism. The validation of the updated mechanism against jet-stirred reactor data is presented, showcasing its effective performance in predicting JSR data.

The importance of properly correcting the electric double layer effect in unravelling the intrinsic kinetics of electrode reactions

Understanding the effects of the electric double layer (EDL) on electrode kinetics is of great importance for improving the performance of electrochemical devices. In this work, by using the HER at Au(111) in x M HClO4 ​+ ​(1−x) M NaClO4 or NaOH as a model reaction, the intrinsic kinetic parameters for HER has been unveiled based on the modified Poisson-Nernst-Planck equations and the Frumkin-Butler-Volmer theory. Our analysis reveals that i) the EDL effects induced changes in proton concentration cH+RP and electric potential ϕRP at the reaction plane are the main reason for the difference of HER current in the cases with x M HClO4 and x M HClO4 ​+ ​(1−x) M NaClO4; ii) the EDL effects are the main origin for the difference in HER current between acidic and alkaline solutions at the Au(111). Our work demonstrates that microkinetic simulation with properly considering the EDL effects is important for unravelling intrinsic reaction kinetics of electrocatalytic reactions.

Polyurethane‐based nanocomposite for catalytic reduction of toxic dyes

AbstractIn this work, we prepared AuNPs loaded polyurethane‐sodium alginate (Au‐PU‐ALg) composite polymers by casting and in‐situ reduction method. Successful fabrication of AuNPs was confirmed by UV–visible, Fourior transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), field emission scanning elcetron microscopy (FESEM), and energy dispersive X‐ray (EDX) analysis along with the change in color of the suspension from yellow to dark purple. Thermo‐gravimetric analysis (TGA) also confirmed the loading of 7.44 % AuNPs of total nanocomposite contents. The catalytic activity of Au‐PU‐ALg nanocomposites was checked by reducing Rhodamine B (RhB) as a model reaction. It was seen that reduction of RhB was successfully done in the presence of NaBH4 and Au‐PU‐ALg nanocomposite in just 8 min with value of kapp found as 0.648 min−1. While the value of kapp for RhB reduction was found as 0.0008, 0.00221, and 0.0008 min−1 in the presence of catalyst, NaBH4 and polymer gel particles, respectively. Thus results show that the value of kapp for the reduction of RhB in the presence of NaBH4 and catalyst was found high as compared to the controlled reactions. Complex mixture of dyes such as RhB, crystal violet (CV), Congo red (CR), and dyes polluted industrial wastewater was become colorless in 10 and 3 min, respectively on mixing with catalyst and reducing agent. It was also observed that reduction of RhB followed pseudo first order kinetic model and Langmuir Hinshelwood mechanism.

Quantum information scrambling and chemical reactions

The ultimate regularity of quantum mechanics creates a tension with the assumption of classical chaos used in many of our pictures of chemical reaction dynamics. Out-of-time-order correlators (OTOCs) provide a quantum analog to the Lyapunov exponents that characterize classical chaotic motion. Maldacena, Shenker, and Stanford have suggested a fundamental quantum bound for the rate of information scrambling, which resembles a limit suggested by Herzfeld for chemical reaction rates. Here, we use OTOCs to study model reactions based on a double-well reaction coordinate coupled to anharmonic oscillators or to a continuum oscillator bath. Upon cooling, as one enters the tunneling regime where the reaction rate does not strongly depend on temperature, the quantum Lyapunov exponent can approach the scrambling bound and the effective reaction rate obtained from a population correlation function can approach the Herzfeld limit on reaction rates: Tunneling increases scrambling by expanding the state space available to the system. The coupling of a dissipative continuum bath to the reaction coordinate reduces the scrambling rate obtained from the early-time OTOC, thus making the scrambling bound harder to reach, in the same way that friction is known to lower the temperature at which thermally activated barrier crossing goes over to the low-temperature activationless tunneling regime. Thus, chemical reactions entering the tunneling regime can be information scramblers as powerful as the black holes to which the quantum Lyapunov exponent bound has usually been applied.

Reductive Doping Inhibits the Formation of Isomerization‐Derived Structural Defects in N‐doped Poly(benzodifurandione) (n‐PBDF)

AbstractRecently, solution‐processable n‐doped poly(benzodifurandione) (n‐PBDF) has been made through in‐situ oxidative polymerization and reductive doping, which exhibited exceptionally high electrical conductivities and optical transparency. The discovery of n‐PBDF is considered a breakthrough in the field of organic semiconductors. In the initial report, the possibility of structural defect formation in n‐PBDF was proposed, based on the observation of structural isomerization from (E)‐2H,2′H‐[3,3′‐bibenzofuranylidene]‐2,2′‐dione (isoxindigo) to chromeno[4,3‐c]chromene‐5,11‐dione (dibenzonaphthyrone) in the dimer model reactions. In this study, we present clear evidence that structural isomerization is inhibited during polymerization. We reveal that the dimer (BFD1) and the trimer (BFD2) can be reductively doped by several mechanisms, including hydride transfer, forming charge transfer complexes (CTC) or undergoing an integer charge transfer (ICT) with reactants available during polymerization. Once the hydride transfer adducts, the CTC, or the ICT product forms, structural isomerization can be effectively prevented even at elevated temperatures. Our findings provide a mechanistic understanding of why isomerization‐derived structural defects are absent in n‐PBDF backbone. It lays a solid foundation for the future development of n‐PBDF as a benchmark polymer for organic electronics and beyond.

Reductive Doping Inhibits the Formation of Isomerization-Derived Structural Defects in N-doped Poly(benzodifurandione) (n-PBDF).

Recently, solution-processable n-doped poly(benzodifurandione) (n-PBDF) has been made through in-situ oxidative polymerization and reductive doping, which exhibited exceptionally high electrical conductivities and optical transparency. The discovery of n-PBDF is considered a breakthrough in the field of organic semiconductors. In the initial report, the possibility of structural defect formation in n-PBDF was proposed, based on the observation of structural isomerization from (E)-2H,2'H-[3,3'-bibenzofuranylidene]-2,2'-dione (isoxindigo) to chromeno[4,3-c]chromene-5,11-dione (dibenzonaphthyrone) in the dimer model reactions. In this study, we present clear evidence that structural isomerization is inhibited during polymerization. We reveal that the dimer (BFD1) and the trimer (BFD2) can be reductively doped by several mechanisms, including hydride transfer, forming charge transfer complexes (CTC) or undergoing an integer charge transfer (ICT) with reactants available during polymerization. Once the hydride transfer adducts, the CTC, or the ICT product forms, structural isomerization can be effectively prevented even at elevated temperatures. Our findings provide a mechanistic understanding of why isomerization-derived structural defects are absent in n-PBDF backbone. It lays a solid foundation for the future development of n-PBDF as a benchmark polymer for organic electronics and beyond.

Cu@SiO2 catalyst with high copper dispersion for chemoselective hydrogenation of p-chloronitrobenzene

Selective hydrogenation of p-chloronitrobenzene (p-CNB) is not only of significant industrial importance, but also an important model reaction for selectivity investigation. Despite non-precious metal Cu has been proven to be an effective promoter in bimetallic catalysts, Cu as a single active metal achieving both high conversion and high selectivity are rare reported. In this work, Cu@SiO2 catalysts with high specific surface area (509.8–694.3 m2/g), high Cu dispersion (58.4–69.6 %), and small particle size (2.0–3.0 nm) has been prepared by a simple sol–gel method. The catalysts completely suppress the dechlorination reaction, achieving complete conversion of p-CNB with 99.9 % selectivity for p-chloroaniline (p-CAN). Its microstructure, composition, chemical state, adsorption and reaction behavior have been identified by various conventional ex-situ characterizations of catalysts and in-situ DRIFTs of hydrogenation of p-CNB. Interestingly, even at high loadings, Cu in the catalyst could be highly dispersed, thus exhibiting good catalytic activity. In addition, the Cu catalyst exhibits unique adsorption performance towards p-CNB, which perhaps one of the factors for its good performance. This work not only provides a selective hydrogenation catalyst with high Cu dispersion even at high loading amount by a simple method and but also reveals the importance of the adsorption mode of p-CNB, providing guidance for the development of more efficient catalysts in the future.

Possibilities and Limitations of Kinetic Studies in On-Surface Synthesis by Real Time X-ray Photoelectron Spectroscopy.

The kinetics of coupling reactions on surfaces can be quantitatively studied in real time by X-ray Photoelectron Spectroscopy (XPS). From fitting experimental data, kinetic reaction parameters such as the rate constant's pre-exponential and activation energy can be deduced and compared to quantum chemical simulations. To elucidate the possibilities and limitations of this approach, we propose studies in which experimental data are first simulated and subsequently fitted. Knowing the exact kinetic parameters used in the simulation allows one to evaluate the accuracy of the fit result. Here, several experimental influences, such as the data point density and the addition of noise, are explored for a model reaction with first-order kinetics. The proposed procedure sheds light on the accuracy with which kinetic parameters can be derived and may also help in the design of future experiments.

A parallel line probe for spatially selective electrochemical NMR spectroscopy

In situ NMR is a valuable tool for studying electrochemical devices, including redox flow batteries and electrocatalytic reactors, capable of detecting reaction intermediates, metastable states, time evolution of processes or monitoring stability as a function of electrochemical conditions. Here we report a parallel line detector for spatially selective in situ electrochemical NMR spectroscopy. The detector consists of 17 copper wires and is doubly tuned to 1H/19F and X nuclei ranging from 63Cu (106.1 MHz) to 7Li (155.5 MHz). The flat geometry of the parallel line detector allows its insertion into a high electrode surface-to-volume electrochemical flow reactor, enabling a detector-in-a-reactor design. This integrated device is named “eReactor NMR probe”. Combined with B1-selective pulse sequences, selective detection of the nuclei at the electrode-electrolyte interface, that is within a distance of 800 μm from the electrode surface, has been achieved. The selective detection of 7Li and 19F nuclei is demonstrated using two electrolytes, LiCl and LiBF4 solutions, respectively. A good B1 homogeneity with an 810° to 90° pulse intensity ratio of 68–72 % was achieved. Using electrochemical plating of lithium metal as a model reaction, we further demonstrated the operando functionality of the probe. The new eReactor NMR probe offers a general method for studying flow electrochemistry, and we envision applications in a wide range of environmentally relevant energy systems, for example, Li metal batteries, electrochemical ammonia synthesis, carbon dioxide capture and reduction, redox flow batteries, fuel cells, water desalination, lignin oxidation etc.