Carbon Bridge Research Articles

High−molecular weight poly(2-substituted 1,3-diene)s using iminopyridine iron precatalysts at high polymerization temperature and low iron loading

The synthesis of a series of iron(II) dichloride complexes bearing iminopyridine (ImPy) ligands, differing in the substituents at the pyridine, bridging carbon and N−aryl ring is described (1-LHPh−7-LHS). The X-ray structures of some of them are presented. All the iron compounds and, for comparison, the already reported 8-LHPhP, that features bulky ortho isopropyl N−aryl substituents, have been investigated as precatalysts for the polymerization of 2-substituted 1,3-dienes, i.e., isoprene and β-myrcene, using a low excess of methylaluminoxane (MAO) as alkylating reagent, iron loading as low as 0.025 mol% and variable temperature up to 100 °C. The goal is to have insights into ligand effects on catalyst reactivity and selectivity and to recognize the most robust iron precatalysts to access high-molecular weight (MW) polymers using low iron loading and high polymerization temperature, which meets current demands of mild, operationally simple approach. Particularly, the ketimine 4-LMePh and 5-LPhPh are more stable and least prone to chain termination than all the aldimine parents. 4-LMePh and 5-LPhPh produce cis-1,4/3,4 ultra-high-MW poly(isoprene)s and solid high-MW poly(β-myrcene)s, while maintaining narrow and unimodal molecular weight distribution. In this study we intentionally kept the monomer conversion low to provide a valuable assessment of catalyst stability, uncorrupted by mass or heat transport limitations. Furthermore, the synthesis of the unsubstituted aminopyridine (AmPy) iron(II) dichloride complex 9-LAPh, analogue to 1-LHPh, is described. 9-LAPh has been demonstrated to be a valuable probe for stability studies. Given the variety of catalytic transformations and substrates for which (ImPy)FeCl2 precatalysts have promising reactivity and selectivity, those developed in this study offer promising applications also beyond the polymerization of 1,3-dienes.

Roles of bridge carbon and heteroatom during the dehydrogenation reaction of dicyclohexylmethane derivatives on Pd and Pt catalysts for liquid organic hydrogen carrier

Liquid organic hydrogen carrier (LOHC) has been developed to overcome the low efficiency of conventional hydrogen storage methods. Although 2-[n-methylbenzyl]pyridine (MBP), one of dicyclohexylmethane derivatives, has been reported as a high-performance LOHC material, its dehydrogenation mechanism has yet to be fully understood. Here, we combine both experiments and theoretical calculations to comparatively elucidate the dehydrogenation mechanism of H12-MBP on Pd and Pt catalysts. The experimental results for hydrogen release from H12-MBP and H6-MBP show that Pd/Al2O3 has a faster initial hydrogen release rate than Pt/Al2O3. Density functional theory calculations reveal that the N-heteroatom in the pyridine ring has a significant effect on the adsorption of H12-MBP. In addition, the hydrogen migration in the pyridine ring serves as the rate-determining step, where the activation free energy of Pd(111) is lower than that of Pt(111). Our results provide insight into the dehydrogenation of heterocyclic compounds with a bridge structure on metal catalysts.

Valence Delocalization and Metal-Metal Bonding in Carbon-Bridged Mixed-Valence Iron Complexes.

The carbide ligand in the iron-molybdenum cofactor (FeMoco) in nitrogenase bridges iron atoms in different oxidation states, yet it is difficult to discern its ability to mediate magnetic exchange interactions due to the structural complexity of the cofactor. Here, we describe two mixed-valent diiron complexes with C-based ketenylidene bridging ligands, and compare the carbon bridges with the more familiar sulfur bridges. The ground state of the [Fe2 (μ-CCO)2 ]+ complex with two carbon bridges (4) is S= , and it is valence delocalized on the Mössbauer timescale with a small thermal barrier for electron hopping that stems from the low Fe-C force constant. In contrast, one-electron reduction of the [Fe2 (μ-CCO)] complex with one carbon bridge (2) affords a mixed-valence species with a high-spin ground state (S= ), and the Fe-Fe distance contracts by 1 Å. Spectroscopic, magnetic, and computational studies of the latter reveal an Fe-Fe bonding interaction that leads to complete valence delocalization. Analysis of near-IR intervalence charge transfer transitions in 5 indicates a very large double exchange constant (B) in the range of 780-965 cm-1 . These results show that carbon bridges are extremely effective at stabilizing valence delocalized ground states in mixed-valent iron dimers.

Organometallic Allene [(μ-C)(Fe(CO)4 )2 ]: Bridging Carbon Showing Transformation from Classical Electron-Sharing Bonding to Double σ-Donor and Double π-Acceptor Ligation.

Allenes (R2 C=C=CR2 ) have been traditionally perceived to feature localized orthogonal π-bonds between the carbon centres. We have carried out quantum-mechanical studies of the organometallic allenes envisioned by the isolobal replacement of the terminal CH2 groups by the d8 Fe(CO)4 fragment. Our studies have identified two organometallic allenes viz. D2d symmetric [(μ-C)(Fe(CO)4 )2 ] (2) and D3 symmetric [(μ-C)(Fe(CO)4 )2 ] (3) with trigonal bipyramidal coordination at the Fe atoms. Compound 2 features the bridging carbon atom in an equatorial position with respect to the ligands on the TM centre, while 3 features the central carbon atom in an axial position. The bis-pseudoallylic anionic delocalisation proposed in the C2-C1-C3 spine of organic allene is retained in the organometallic allene 2, and is transformed to a typical three-centre bis-allylic anionic delocalisation in the organometallic allene 3. The topological analysis of electron density also indicates a bis-allylic anionic type delocalisation in the organometallic allenes. The quantitative bonding analysis using the EDA-NOCV method suggests a transition from classical electron-sharing bonding between the central carbon atom and the terminal groups in 1 to donor-acceptor bonding in 3. Meanwhile, both electron-sharing and donor-acceptor bonding models are found to be probable heuristic bonding representations in the organometallic allene 2.

Scalable synthesis of MOF-derived Nd2O3@C and V2O5@C nanohybrid: Efficient electrocatalyst for OER in alkaline medium

Craving to search for renewable energy reservoirs for the development of green and robust electrocatalysts, now become essential for catalytic performance by using energy conversion devices. Herein, we fabricated a metal–organic framework (MOF) derived transition metal and rare earth metal oxides-based materials for water electrocatalysis. MOF is regarded as the potential hotspot to increase catalytic activity through fascinating chemical and structural traits. This study summarizes the oxygen evolution reaction (OER) of MOF-derived Nd2O3@C and V2O5@C by depositing them on stainless steel substrate (SS) in an alkaline medium. The grown electrocatalysts Nd2O3, V2O5, Nd-MOF, V-MOF, and MOF-derived Nd2O3@C and V2O5@C probed by various useful techniques to confirm oxidation states, phase-changing, structural, morphological, and compositional properties. The MOF-derived Nd2O3@C and V2O5@C formed irregular spherical shaped and nanorod-like morphology, respectively, which proved helpful for the easy transfer of electrons to enhance OER. The electrochemical study indicates that among all electrocatalysts, the V2O5@C electrode exhibits remarkable electrochemical results having low overpotential (282 mV), and smaller Tafel slope of 60 mVdec-1 at a current density of 10 mAcm−2, exhibiting that the transition metal based MOF has good efficiency as compared to the rare earth metal MOF. The grown catalysts enable additional reaction sites and open up new channels, besides it approaches quick electron transfer in V2O5@C through a carbon bridge. Thus, the porous skeleton of the resulting hybrid catalyst showed superior electrical conductivity, boosting electrochemical properties and making it an efficient and durable electrocatalyst for industrial-scale water electrolysis.

Model construction and optimization of coal molecular structure

Understanding the structural characteristics of coal molecular at the molecular level is of paramount importance for the effective utilization of coal. In this work, the molecular structure of coal sample, from Liuzhuang(LZ) Coal Mine in Anhui Province, China, is investigated using modern analytical techniques, such as elemental analysis, X-ray photoelectron spectroscopy (XPS),Fourier Transform Infrared Spectroscopy(FT-IR) and Solid 13C nuclear magnetic resonance spectroscopy (13C NMR). It is found that the aromatic compounds of LZ coal are mainly in the form of 2 and 3 rings, with an aromaticity of 40.99% and the ratio of aromatic bridge carbon to aromatic peripheral carbon is 0.232. sulfur element is too low to considered in the model. Based on the above analysis, the molecular formula of LZ coal is inferred as C158H143O35N7. The experimental 13C NMR is consistent with the simulated spectrum, which indicates the accuracy of LZ molecular structure model. The molecular structure model is constructed and optimized by using classical molecular dynamics and the density functional based tight-binding method to obtain the lowest energy and most stable conformation, respectively. The optimized model has a more prominent steric configuration, but the lamellar structure of the aromatic layer is arranged in a more disordered manner. The experimental FT-IR spectra of the model are in preferably good agreement with the simulated results, which proves the correctness of LZ molecular structure. The molecular structure of LZ mine coal established in this paper can provide basic scientific data for further investigation of gas adsorption and resolution in coal seams at the atomic and molecular scales. Overall, Compared to contemporary technologies, these results show a good comparability among the different techniques and therefore provide comprehensive, accurate analytical technique to analyze the molecular structure of coal.

The effect of weld groove variations on the toughness of welding joints of AISI 1050 material

SMAW (Shielded Metal Arc Welding) welding is a metal joining process that uses heat energy to melt the workpiece and electrode (fill material). The flux material used for type E7016, a low hydrogen electrode wire typically used for welding heavy-duty plates and structures. Its use is for welding medium carbon steel, bridges, ships and machinery. The result of welding electrode E7016 is very smooth, deep penetration, crack resistant, ductile, good weld appearance and stable arc, the material used in the SMAW welding process is AISI 1050 steel. While AISI 1050 steel is steel that has a carbon content of 0.50 % so that it is classified as medium carbon steel. This steel is widely used in the market because it has many advantages, one of which is as an automotive component. This steel has the characteristics of good machinability, good wear resistance and medium mechanical properties. This study aims to determine the shock strength (impact) and the difference in the time of making weld grooves on SMAW welding results on AISI 1050 steel with variations of Double Bevel and Double V Groove grooves. In testing in the Weld Metal area with a current used of 110 Ampere. From the tests that have been carried out, it is known that the value of the highest impact strength is in the Double Bevel groove which has a value of 1.91 Joule/mm2, for the manufacture of welded grooves where the Double Bevel time is shorter than Double V Groove, so the time produced by Double Bevel which is 3.44 minutes/second.

Robust carbon bridge to construct double-shell FeCo@C@Al2O3 heterogeneous structure with dual-function for extraordinary microwave absorption and anti-corrosion

The complexity of the environment leads to corrosion and failure of absorbing functions. The encapsulation and surface modification of multi-gradient structures are typical ways to address this challenge. Herein, a FeCo@C@Al2O3 core–shell heterostructure is developed for the dual functions of absorbing and anti-corrosion using the chemical vapor deposition and hydrolysis of the aluminum sulfate. This unique double-shell structure provides more multiple interface relaxation polarizations, electromagnetic wave scatterings. And the robust carbon layer produces sufficient conduction loss for the FeCo@C@Al2O3. Compared with pure FeCo, the absorption capacity of FeCo@C@Al2O3 increases up to 1.4 times, the minimum reflection loss value achieves −46.7 dB at the thickness of 1.4 mm. And the maximum effective absorption bandwidth is up to 9.3 GHz. While it possesses minimum total RCS value of −13.29 dB∙m2, reflecting the optimal absorbing stealth performance. Besides, the coating Al2O3 layer effectively isolates the diffusion of corrosion ions including Cl-, H2O and O2, the corrosion current and polarization resistance of FeCo@C@Al2O3 are well adjusted to 7.96 × 10-8 A/cm2 and 5.40 × 105 Ω·cm2, respectively. Therefore, the FeCo@C@Al2O3 heterostructure provides an updated platform for the research and development of new absorbing and anti-corrosion materials.

Experimental and theoretical study on molecular structure construction of Hongliulin coal

A suitable model can reflect the properties of coal well. In this study, the properties of HongLiuLin (HLL) coal were studied through industrial analysis, XPS, 13C NMR and FTIR. The results show the coal has middle-rank bituminous coal characteristics, and the ratio of aromatic bridge carbon to aromatic peripheral carbon is 0.16. Benzene and naphthalene ring are the main components of the aromatic structure. N and S exist in pyrrole nitrogen and fatty sulfur, respectively. The hypothesis method was used to deduce the molecular formula C130H73O21NS of the coal model. The stability of the carbon skeleton was improved through the Van Der Waals (VDW) forces in non-bonding energy. Verification of NMR, FTIR and density was completed based on quantum chemistry and molecular mechanics. The coal model energy level orbitals analysis shows that the LUMO and HOMO orbitals are located in the aromatic functional groups. This work provides a reference for further research on the nature of coal in north Shaanxi and improving the utilization rate of coal.

N-Doped Yolk–Shell Carbon Nanospheres with “Carbon Bridges” for Supercapacitors

N-doping multilocular carbon spheres are beneficial to improving the electrical property due to their unique pore structure and elemental composition; nevertheless, there is a great challenge to fabricate this structure in a facile way. In this work, an N-doping yolk–shell carbon nanosphere with a “carbon bridges” structure was prepared by domain-limited carbonization of RF@SiO2 (RF = resorcinol-formaldehyde resin) with ethylenediamine (EDA) as the nitrogen precursor. The structure of the “carbon bridges” and the carbon shell’s thickness can be adjusted by controlling the thickness of the silica layer, resulting in a change in morphology (from dense nanospheres to yolk–shell nanospheres). The optimized yolk–shell carbon nanospheres (C@C-2 nanospheres) exhibited high N-doping, an abundant micro-mesoporous structure, and an optimum “carbon bridges” structure, contributing to a high-rate capability in a supercapacitor, which was reflected in the energy storage dynamics. Herein, C@C-2 nanospheres, as an electrode material for supercapacitors, presented a reversible specific capacitance of 373.3 F g–1 at 0.5 A g–1 in 2 M KOH and retained a well-advanced capacitance retention capability (95.8%) at 4 A g–1 for more than 10,000 cycles. This work sheds light on an avenue to design high-performance porous carbons for efficient energy storage.

Vanadium (III) catalysts with bulky Bis-NHCs ligands for ethylene-norbornene (co)polymerization

A series of vanadium catalysts with bulky bis(N-heterocyclic carbenes) (bis-NHCs) ligands were synthesized by in-situ reaction. With diethylaluminum chloride (AlEt2Cl) as cocatalyst and ethyl trichloroacetate (ETA) as activator, these catalysts exhibit good activity when used to catalyze ethylene (co)polymerization. The structure of the catalyst, especially the bridging carbons number of the bis-NHCs ligands, is related to the performance of the (co)polymer. When the bis-NHCs ligand with tBu substituted, increased the bridging carbons number of the bis-NHCs ligand is easier to obtain higher molecular weight polymers. But when the bis-NHCs ligand with 2,6-diisopropyl phenyl substituted, the increase of the bridging carbons number is not conducive to obtaining higher molecular weight polymers. Under the same concentration of comonomer, the increase of the bis-NHCs ligand bridged carbon number of the V-complexes is more beneficial to obtain the copolymer with high norbornene (NB) content.

Chromium-Based Complexes Bearing Aminophosphine and Phosphine-Imine-Pyrryl Ligands for Selective Ethylene Tri/Tetramerization.

A series of Cr-based complexes 6-10 bearing aminophosphine (P,N) ligands Ph2P-L-NH2 [L = CH2CH2 (1), L = CH2CH2CH2 (2), and L = C6H4CH2 (3)] and phosphine-imine-pyrryl (P,N,N) ligands 2-(Ph2P-L-N=CH)C4H3NH [L = CH2CH2CH2 (4) and L = C6H4CH2 (5)] were prepared, and their catalytic properties were examined for ethylene tri/tetramerization. X-ray crystallographic analysis of complex 8 indicated the κ2-P,N bidentate coordination mode at the Cr(III) center and the distorted octahedral geometry of monomeric P,N-CrCl3. Upon activation by methylaluminoxane (MAO), complexes 7-8 bearing P,N (PC3N backbone) ligands 2-3 showed good catalytic reactivity for ethylene tri/tetramerization. On the other hand, complex 6 bearing the P,N (PC2N backbone) ligand 1 was found active for non-selective ethylene oligomerization, while complexes 9-10 bearing P,N,N ligands 4-5 only produced polymerization products. In particular, the high catalytic activity of 458.2 kg/(g·Cr·h), excellent selectivity of 90.9% (1-hexene and 1-octene combined), and extremely low PE content of 0.1% were obtained with complex 7 in toluene at 45 °C and 45 bar. These results suggest that rational control of P,N and P,N,N ligand backbones, including a carbon spacer and rigidity of a carbon bridge, can lead to the high-performance catalyst for the ethylene tri/tetramerization process.

Biochar doped carbon nitride to enhance the photocatalytic hydrogen evolution through synergy of nitrogen vacancies and bridging carbon structure: Nanoarchitectonics and first-principles calculation

Enhancing the separation and transfer of photogenerated carries is vital for improving the efficiency of photocatalytic hydrogen evolution reaction (HER) of graphitic carbon nitride (g-C3N4). Herein, a carbon-rich g-C3N4 with nitrogen vacancies (CCN4) was constructed by incorporating the biochar into g-C3N4 during a thermal polymerization in N2 atmosphere. The doped carbon atoms replaced the bridged nitrogen and increased the delocalization π states. The synergy of the enhanced π states and nitrogen vacancy favored narrowing the bandgap and accelerating the charge separation and migration in catalyst. Meanwhile, the CCN4 catalyst had favorable kinetics for HER, with simpler steps and a lower energy barrier than the PCN sample, in which H2 production from *H is prior to OH generation. The CCN4 catalyst exhibited excellent HER activity with a hydrogen evolution rate of 3342.4 μmol∙g−1∙h−1 with 0.5 wt% cocatalyst Pt, which was 5.1 times higher than that of pristine g-C3N4 (PCN). Additionally, CCN4 exhibited good resistance to salt with the concentration near that of natural seawater, showing the further improved hydrogen evolution rate of 3808.8 μmol∙g−1∙h−1. The findings reported in this work shed light on a biochar-tailored protocol to control the defects of g-C3N4 and optimize its intrinsic electronic properties and photocatalytic HER.

Synthesis, antitumor activities and functional mechanism of purine derivatives harboring phenyl moieties through three carbon bridges

Synthesis, antitumor activities and functional mechanism of purine derivatives harboring phenyl moieties through three carbon bridges

Designing Excess Electron Compounds by Substituting Alkali Metals to a Small and Versatile Tetracyclic Framework: A Theoretical Perspective.

Organic compound-based nonlinear optical (NLO) materials have sparked a lot of attention due to their multitude of applications and shorter optical response times than those of inorganic NLO materials. In the present investigation, we designed exo-exo-tetracyclo[6.2.1.13,6.02,7]dodecane (TCD) derivatives, which were obtained by replacing H atoms of methylene bridge carbon with alkali metals (Li, Na, and K). It was observed that upon the substitution of alkali metals at bridging CH2 carbon, absorption within the visible region occurred. Moving from 1 to 7 derivatives, the maximum absorption wavelength of the complexes exhibited a red shift. The designed molecules showed a high degree of intramolecular charge transfer (ICT) and excess electrons in nature, which were responsible for rapid optical response time and significant large molecular (hyper)polarizability. Calculated trends also inferred that the crucial transition energy decreased in order that also played a key role in the higher nonlinear optical response. Furthermore, to examine the effect of the structure/property relationship on the nonlinear optical properties of these investigated compounds (1-7), we calculated the density of state (DOS), transition density matrix (TDM), and frontier molecular orbitals (FMOs). The largest first static hyperpolarizability (βtot) of TCD derivative 7 was 72059 au, which was 43 times greater than that of the prototype p-nitroaniline (βtot = 1675 au).

Construction of macromolecular model and analysis of oxygen absorption characteristics of Hongyang No. 2 coal mine

Understanding the molecular structure characteristics of coal from the molecular level is of great significance for realizing rational utilization and efficient transformation of coal. The molecular structure of coal samples from 1304 working face in No.13 coal seam of Hongyang No.2 Mine (HY) was studied by industrial analysis, elemental analysis, Nuclear magnetic resonance carbon spectroscopy (13C NMR) and Fourier transform infrared spectroscopy (FTIR). The results show that the aromatic compounds in coal samples of HY are mainly naphthalene ring structures. The aliphatic structure mainly consists of methyl, ethyl side chains and cycloalkanes. The ratio of aromatic bridge carbon to weekly carbon in molecular structure is 0.17. Oxygen atoms exist in the form of carbonyl, hydroxyl, and ether bonds, nitrogen atoms exist in the form of pyridine and pyrrole respectively, and sulfur atoms exist in the form of thiophene. Based on this, the planar structure model of coal macromolecule in HY is constructed, and its molecular formula is C129H88O29N2S, and its molecular weight is 2160. The structure optimization and annealing kinetics simulation of a single macromolecule model were carried out, and a stable three-dimensional coal model of HY was obtained. In addition, the oxygen absorption characteristics of coal samples in HY were studied by molecular dynamics and quantum chemistry. The results show that the adsorption capacity of the Wiser model is less than that of HY coal model. This is because, compared with the Wiser model, the content of oxygenated aliphatic hydrocarbons in the molecular structure of HY coal is higher, and the condensation degree of polycyclic aromatic hydrocarbons is lower. Due to the stronger physical adsorption capacity of hydroxyl, ether bond, and carbonyl on O2, HY Mine has stronger physical adsorption capacity on O2.

Carbon-deuterium bonds as reporters of electric fields in solvent and protein environments.

Use of vibrational probes to measure electric fields inside proteins has illuminated the role of electrostatics in biological applications ranging from binding interactions to enzyme catalysis. While prior work focused on strongly absorbing carbonyl and nitrile probes, more recent work has begun exploring weakly absorbing carbon-hydrogen bonds, beginning with measurements of electric fields inside oxidoreductases using the vibrational Stark effect (VSE). Originally, an alcohol dehydrogenase inhibitor containing a deuterated aldehyde was used to measure the field in two directions—on carbonyl and carbon-deuterium (C-D) bonds—in the enzyme active site. Now, several more distinct cases demonstrate how C-D probes map electric fields to vibrational frequency shifts, with new implications for our understanding of the VSE. To probe the field along a different dimension in oxidoreductases, we consider singly deuterated NAD(P)H which reports fields along the hydride transfer axis and whose frequency detection is facilitated by advancements in quantum cascade laser (QCL) technology for infrared spectroscopy. Unusually, the solvatochromic shift for this C-D probe appears opposite to that observed for carbonyls and nitriles; that is, the probe blueshifts in more polar solvents. In another example, the chromophore of green fluorescent protein (GFP) with a deuterated bridge carbon demonstrates similarly unusual frequency shifts in solvent and protein environments, with stronger fields parallel to the C-D dipole causing blueshifts. Observed Stark tuning rates for these molecules are recapitulated by in silico Stark calculations at the B3LYP or ωB97X-D/6-31+G(d) level. Stark tuning rate comparison with other C-D containing molecules including deuterated aldehydes and chloroform-d indicates a large sensitivity of the Stark tuning rate to molecular structure. We demonstrate how properly calibrated C-D probes can be effective reporters of electric fields in applications such as enzyme-catalyzed hydride transfer, biological photophysics and beyond.

Understanding the molecular structure of Datong coal by combining experimental and computational study

Understanding the structure of coal is crucial to explain its chemical reactivity. In order to study the microstructure characteristics of coal in-depth, ultimate analysis, solid-state 13C nuclear magnetic resonance (13C-NMR), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) are used to analyze the Datong coal. The results show that the aromaticity of Datong coal is 62.60%, and the ratio of aromatic bridge carbon to aromatic peripheral carbon is 0.238, indicating that more naphthalene and anthracene are in the aromatic structure of coal. Hydroxyl (C–O), carbonyl (C=O) and carboxyl (COO–) are the main oxygen-containing groups in coal, and the nitrogen element mainly exists in the form of pyrrole and pyridine. The main substitution modes on the benzene ring are di- and tri-substituted. Based on the above analysis, the 2D and 3D macromolecular models are constructed and optimized by using computer-aided modeling. The model is verified by 13C-NMR and FTIR spectra with density functional theory calculations. The coal molecular formula is defined as C149H112O24N2. The reaction sites in coal structure are oxygen-containing functional groups and aliphatic structures (–CH, –CH2). Therefore, the molecular structure of Datong coal has been systematically described and understood at the molecular level based on experimental data and quantum chemical calculations.

Multifunctional lithium compensation agent based on carbon edges catalysis and its application in anode-free lithium batteries

Lithium compensation agents, especially the self-sacrificing salts, can effectively compensate for the irreversible capacity loss of lithium-ion battery, but most lithium compensation materials only have the function of lithium compensation and their mechanisms are still unknown. In this study, a method for preparing multifunctional lithium compensation agent Li2C4O4 (lithium squarate) microspheres using spray drying to extend the cycle life of anode-free batteries is proposed, and the catalytic effect of the carbon edges on Li2C4O4 decomposition was evaluated. The Li2C4O4 microspheres can release additional capacity via decomposition and produce CO2 to improve the stability of the battery, as well as generate carbon bridges at the carbon edges to improve the rate performance of the battery. When it was applied to LiFePO4 battery system, the capacity increased from 60 mAh/g to 90 mAh/g at a current density of 10C. When applied to a Cu||LiFePO4 anode-free battery, an active lithium reserve layer formed on the surface of copper foil through Li2C4O4 decomposition, thus prolonging the cycling performance of the battery without any surface modification. After 40 turns at a current density of 0.1C, the cycling capacity retention was higher than 96%.

Asymmetric iminium ion-catalyzed conjugate addition of 2-hydroxycinnamaldehydes and 2-oxocarboxylic esters: synthesis of chiral polysubstituted bridged bicyclic ketals.

A highly regio-, chemo-, and stereoselective cascade process initiated by enantioselective iminium-catalyzed conjugate addition of 2-hydroxycinnamaldehydes and 2-oxocarboxylic esters is presented. Normal cinnamaldehydes are not reactive under the same reaction conditions. Bridged bicyclic ketals rather than acetals bearing stereocenters on both the bridge carbon and bridgehead ketal carbon are synthesized.