Ni-catalyzed carbon–carbon bonds cleavage of mixed polyolefin plastics waste

The inert carbon–carbon(C–C) bonds cleavage is a main bottleneck in the chemical upcycling of recalcitrant polyolefin plastics waste. Here we develop an efficient strategy to catalyze the complete cleavage of C–C bonds in mixed polyolefin plastics over non-noble metal catalysts under mild conditions. The nickelbased catalyst involving Ni_(2)Al_(3) phase enables the direct transformation of mixed polyolefin plastics into natural gas, and the gas carbon yield reaches up to 89.6%. Reaction pathway investigation reveals that natural gas comes from the stepwise catalytic cleavage of C–C bonds in polypropylene, and the catalyst prefers catalytic cleavage of terminal C–C bond in the side-chain with the low energy barrier.Additionally, our developed approach is evaluated by the technical economic analysis for an economically competitive production process.

Copper-Catalyzed C-C(O)C Bond Cleavage of Monoalkylated β-Diketone: Synthesis of α,β-Unsaturated Ketones

A new and simple route for the synthesis of α,β-unsaturated ketones via cleavage of the C-C(O)C single bond of monoalkylated β-diketone has been described. The reaction was catalyzed by copper, a cheap transition metal in a weakly basic medium (K3PO4) at room temperature. To carry out this study, we first had to synthesize the monoalkylated β-diketones 1. Afterwards, α,β-unsaturated ketones 2 were obtained with high yields around 80%. Finally, all the products were characterized by 1H NMR, 13C NMR, and HRMS spectra. .

Structural and electronic effects boosting Ni-doped Mo_(2)C catalyst toward high-efficiency C-O/C-C bonds cleavage

The selective cleavage of C-O and C-C is facing a challenge in the field of catalysis.In the present work,we studied the influence of doped Ni on the structure and electronic properties,as well as the selective C-O/C-C bond cleavages in the hydrodeoxygenation of palmitic acid over Ni-Mo_(2)C catalyst.The catalytic activity on Ni doped Mo_(2)C with TOF of 6.9×10^(3)h^(-1)is much superior to intrinsic Mo_(2)C catalyst,which is also higher than most noble metal catalysts.Structurally,the doped Ni raises the active particle dispersion and the coordination numbers of Mo species(Mo-C and Mo-O),improves the graphitization degree to promote the electron transfer,and increases the amount of Lewis and Br?nsted acid,which are responsible for the excellent hydrodeoxygenation performance.The Ni promotes simultaneously C-O and C-C bonds cleavage to produce pentadecane and hexadecane owing to the increase of electron-rich Mo sites after Ni doping.These findings contribute to the understanding of the nature of Ni-doped Mo_(2)C on the roles as catalytic active sites for C-O and C-C bonds cleavage.

Interface defect induced upgrade of K-storage properties in KFeSO4Fcathode: From lowered Fe-3d orbital energy level to advancedpotassium-ion batteries

KFeSO_(4)F(KFSF)is considered a potential cathode due to the large capacity and low cost.However,the inferior electronic conductivity leads to poor electrochemical performance.Defect engineering can facilitate the electron/ion transfer by tuning electronic structure,thus providing favorable electrochemical performance.Herein,through the regulation of surface defect engineering in reduced graphene oxide(rGO),the Fe–C bonds were formed between KFSF and rGO.The Fe–C bonds formed work in regulating the Fe-3d orbital as well as promoting the migration ability of K ions and increasing the electronic conductivity of KFSF.Thus,the KFSF@rGO delivers a high capacity of 119.6 mAh g^(-1).When matched with a graphite@pitch-derived S-doped carbon anode,the full cell delivers an energy density of 250.5 Wh kg^(-1) and a capacity retention of 81.5%after 400 cycles.This work offers a simple and valid method to develop high-performance cathodes by tuning defect sites.

KVPO_(4)F/carbon nanocomposite with highly accessible active sites and robust chemical bonds for advanced potassium-ion batteries

KVPO_(4)F(KVPF)has been extensively investigated as the potential cathode material for potassium-ion batteries(PIBs)owing to its high theoretical capacity,superior operating voltage,and three-dimensional Kt conduction pathway.Nevertheless,the electrochemical behavior of KVPF is limited by the inherent poor electronic conductivity of the phosphate framework and unstable electrode/electrolyte interface.To address the above issues,this work proposes an infiltration-calcination method to confine the in-situ grown KVPF into the mesoporous carbon CMK-3(denoted KVPF@CMK-3).The assembled KVPF@CMK-3 nanocomposite features three-dimensional interconnected carbon channels,which not only offer abundant active sites and significantly accelerate K t/electron transport,but also prevent the growth of KVPF nanoparticle agglomerates,hence stabilizing the structure of the material.Additionally,V–F–C bonds are created at the interface of KVPF and CMK-3,which reduce the loss of F and stabilize the electrode interface.Thus,when tested as a cathode material for PIBs,the KVPF@CMK-3 nanocomposite delivers superior reversible capacitiy(103.2 mAh g^(-1) at 0.2 C),outstanding rate performance(90.1 mAh g^(-1) at 20 C),and steady cycling performance(92.2 mAh g^(-1) at 10 C and with the retention of 88.2%after 500 cycles).Moreover,its potassium storage mechanism is further examined by ex-situ XRD and ex-situ XPS techniques.The above synthetic strategy demonstrates the potential of KVPF@CMK-3 to be applied as the cathode for PIBs.

Clean production of lactic acid by selective carbon-carbon bond cleavage of biomass feedstock over a novel carbon-bismuth oxychloride photocatalyst

The use of functional materials such as carbon-bismuth oxyhalides in integrated photorefineries for the clean production of fine chemicals requires restructuring.A facile biomass-assisted solvothermal fabrication of carbon/bismuth oxychloride nanocomposites(C/BiOCl)was achieved at various temperatures.Compared with BiOCl and C/BiOCl-120,C/BiOCl-180 exhibited higher crystallinity,wider visible light absorption,and a faster migration/separation rate of photoinduced carriers.For the selective C–C bond cleavage of biomass-based feedstocks photocatalyzed by C/BiOCl-180,the xylose conversion and lactic acid yield were 100%and 92.5%,respectively.C/BiOCl-180 efficiently converted different biomass-based monosaccharides to lactic acid,and the efficiency of pentoses was higher than that of hexoses.Moreover,lactic acid synthesis was favored by all active radicals including superoxide ion(·O_(2)^(−)),holes(h^(+)),hydroxyl radical(·OH),and singlet oxygen(^(1)O_(2)),with·O_(2)^(−)playing a key role.The fabricated photocatalyst was stable,economical,and recyclable.The use of biomass-derived monosaccharides for the clean production of lactic acid via the C/BiOCl-180 photocatalyst has opened new research horizons for the investigation and application of C–C bond cleavage in biomass-based feedstocks.

Enhancement of CH_(3)CO^(*) adsorption by editing d-orbital states of Pd to boost C–C bond cleavage of ethanol eletrooxidation

Improving the complete ethanol electrooxidation on Pd-based catalysts in alkaline media has drawn widely attention due to the high mass energy density.However,the weak adsorption energy of CH_(3)CO^(*) on Pd restricts the C–C bond cleavage.Inspired by the molecular orbital theory,we proposed the d-state-editing strategy to construct more unoccupied d-states of Pd for the enhanced interaction with CH_(3)CO^(*) to break C–C bonds.As expected,the reduced number of e_g electrons and more unoccupied d-states of Pd successfully formed on as-prepared porous Rh Au–Pd Cu nanosheets(PNSs).Theoretical calculations show that the optimized d-states of Rh Au–Pd Cu PNS can effectively improve the adsorption of CH_(3)CO^(*) and drastically reduce the energy barrier of C–C bond cleavage,thus boosting the complete oxidation of ethanol.The charge ratio of C_1 pathway on Rh Au–Pd Cu PNSs is 51.5%,more than 2 times higher than that of Pd NSs.Our finding provides an innovative perspective for the design of highly-efficient noble-based electrocatalysts.

可见光催化CO_(2)参与的芳基烯烃碳碳双键断键羧基化反应

烯烃广泛存在于自然界中,在医药、农药和材料等领域具有重要应用.烯烃的C=C键断裂和转化是许多工业过程的基础,可以实现烃类资源的重组与利用.目前,C=C键参与的氧化裂解和烯烃复分解反应已有广泛的研究.相比而言,C=C键参与的还原裂解虽然是烯烃与一系列亲电试剂反应合成功能分子的重要途径,但受限于烯烃自身结构和反应特点,该过程存在较大的挑战,目前研究很少.CO_(2)具有储量丰富、廉价易得、无毒且可循环再生等优点,是合成多种大宗化学品及精细化学品的理想碳一资源.然而,CO_(2)由于热力学稳定性及动力学惰性,在温和条件下难以高效、高选择性转化.因此,利用CO_(2)参与烯烃C=C键还原裂解,选择性构建高值化合物,是一个重要且具有挑战性的研究方向.近年来,可见光催化由于具有反应条件温和、官能团兼容性高等优点,为有机合成等领域提供了新的发展机遇.本文利用二环己基甲基胺作为电子给体,成功实现了可见光催化CO_(2)参与的芳基烯烃C=C键断键羧基化反应.该反应成功的关键在于,二环己基甲基胺既能高效还原淬灭激发态光敏剂并参与烯烃的胺基烷基-羧基化反应,又不明显抑制胺基烷基化中间体对激发态光敏剂的还原淬灭.研究结果表明,多种不同取代(如给电子基和吸电子基)的芳基烯烃均可与CO_(2)发生羧基化反应,高效高选择性地构建了一系列官能团丰富的芳基乙酸类化合物(如萘普生等药物分子).该方法具有反应条件温和(1 atm,室温)、官能团耐受性好以及可用于合成药物衍生物等特点.此外,本文通过氘代实验等机理研究和密度泛函理论计算证明,胺甲基羧化中间体、苄基自由基和苄基碳负离子都是该反应的关键中间体,并提出了可能的反应机理:首先,二环己基甲基胺还原淬灭激发态光敏剂,产生α-胺基碳自由基,与芳基烯烃发生自由基加成反应,得到苄基自由基,进而被还原态光敏剂还原为碳负离子,对CO_(2)亲核进攻得到烯烃的胺基烷基-羧基化中间体;作为电子给体,该中间体可以淬灭另一分子的激发态光敏剂,并通过分子内去质子化过程,产生α-胺基碳自由基物种,进而经历自由基型β-C断裂,生成热力学更稳定的羧基化苄基自由基,从而实现了烯烃C=C键的还原裂解;最后,新产生的苄基自由基被进一步还原为碳负离子,经历质子化过程后得到目标产物.综上,本文以还原裂解的方式丰富了C=C键断键官能团化反应领域,在温和条件下实现了CO_(2)的高效高选择性转化,合成了高附加值的芳基乙酸类化合物,阐明了反应机制,为烯烃和CO_(2)的同时高值化利用提供了新思路,为后续相关反应的开发和应用提供参考.

在过渡金属催化剂上的C―C键断裂以实现生物质的升级

将当前能源生产和消费结构从过度依赖化石能源转变为高效利用可再生能源,是解决能源危机、实现碳中和的有效途径。生物质是最有前途的可再生能源之一,可以取代化石燃料以获得有价值的有机化合物。近年来,大力利用生物质能已成为一种必然趋势。用于生物质转化的传统热化学催化方法通常需要高温、高压等恶劣条件,甚至还需要外部氢或氧源。相比之下,在相对温和的条件下进行的生物质有机分子电催化转化为生产高价值化学品提供了一种绿色高效的策略。特别是,通过C―C键裂解将生物质衍生的分子转化为高价值的短链化学品至关重要。近年来,大量的研究证明过渡金属(TM)电催化剂由于其丰富的三维电子结构和独特的eg轨道增强了过渡金属-氧之间的共价键合,从而在有机物的C―C键断裂中起着至关重要的作用。此外,TM电催化剂的配位环境或电子结构会影响产物的选择性。毫无疑问,明确的反应活性位点和途径有助于深入理解催化剂结构与反应活性之间的构效关系。然而,TM电催化剂介导的生物质衍生有机分子的C―C键裂解反应用于生物质升级的研究目前尚处于起步阶段,其反应机理和催化反应过程尚不清楚。因此,有必要在原子水平上系统地了解电催化剂在C―C键裂解过程中的作用。在本综述中,我们首先依次介绍了广泛研究的TM电催化剂介导的生物质衍生有机分子(包括甘油、环己醇、木质素和糠醛)的C―C键裂解反应,并给出了一些典型的例子和相应的反应途径。然后,系统回顾了过渡金属化合物催化C―C键裂解的反应机理,揭示了界面行为,并构建了TM电催化剂的结构与裂解反应活性之间的构效关系。最后,我们简要总结了上述内容,并强调了在TM电催化剂上研究C―C键裂解的挑战和展望。我们期望这项工作可以为生物质的可控转化和合理设计C―C键裂解的TM电催化剂提供指导。

Molecular Dynamics Simulation Study of CIF in Water： Halogen Bonding Interaction in Liquid

Does the halogen bonding interaction co-exist in liquid when it competes with the hydrogen bonding interaction？ The classical molecular dynamics simulations for the solvation properties of CLF molecule in water are performed with the Lennard-Jones plus Coulomb electrostatic potential parameters that are optimized with ab initio interaction energy calculations for the pre-reactive H2O-CLF complex. We find that the halogen bonding interactions occur between O and CL atoms and have the comparable strength and population with respect to the hydrogen bonding interactions of C1...H.

Density Functional Studies of the Reaction of Ytterbium Monocation with Fluoromethane:C-F Bond Activation and Electron-Transfer Reactivity

The potential energy surface and reaction mechanism corresponding to the reaction of ytterbium monocation with fluoromethane, which represents a prototype of the activation of C-F bond in fluorohydrocarbons by bare lanthanide cations, have been investigated for the first time by using density functional theory. A direct fluorine abstraction mechanism was revealed, and the related thermochemistry data were determined. The electron-transfer reactivity of the reaction was analyzed using the two-state model, and a strongly avoided crossing behavior on the transition state region was shown. The present results support the reaction mechanism inferred from early experimental data and the related thermochemistry data can provide a guide for further experimental researches.

C-F键核自旋偶合常数的理论研究

利用密度泛函中B3LYP方法 ,选择 6 31G 基组 ,研究了四组分别为 1 0、2 0、30、40个分子的C F键的核自旋偶合常数 ,由此拟合出 4个计算核自旋偶合常数的公式 ,并用 4种化合物分别进行检验 ,理论计算值较好地与文献值相符合 .

ECR-CVD沉积a-C∶F薄膜

采用电子回旋共振等离子体化学气相沉积 (ECR CVD)技术 ,用苯和三氟甲烷混合气体 ,制备了氟化非晶碳膜 (a C∶F)。用红外吸收光谱 (FTIR)和X射线光电子能谱 (XPS)分析了a C∶F薄膜的结构。FTIR结果表明 ,氟主要以C—F、CF2 的形式成键形成a C∶F薄膜 ;XPS结果进一步证明a C∶F膜中存在C—F、CF2 键 。

Al_2O_3催化下的取代β-羟基胺Schiff碱衍生物的C—C键裂解反应

探讨了中性Al2O3催化下的取代β-羟基胺Schiff碱衍生物的C—C键裂解反应,结果表明,在Al2O3存在下,由取代苯甲醛与1,2-二苯基-2-氨基乙醇形成的亚胺类化合物很容易通过逆ene反应过程发生α,β-C—C键断裂,且反应不受芳醛分子中邻位基团的影响.通过跟踪反应进程,提出了可能的反应机理.

氢键活化的苯环上C-F键的亲核取代反应研究

以2,4,5-三氟苯乙酮在氢化钠作用下与碳酸二乙酯反应制得3,4-二氟-6-乙氧基苯甲酰乙酸乙酯(2);2经对甲基苯磺酸催化水解脱羧,合成3,4-二氟-6-乙氧基苯乙酮(3)路线为模型,研究了苯环上C-F键的亲核取代反应。实验结果证明,在形成分子内氢键的活化作用下,苯环上的C-F键能够被烷氧负离子亲核取代。2和3的结构经1HNMR,19FNMR和MS表征。

Electro-reductive carboxylation of acyclic C(sp^(3))–C(sp^(3))bonds in aromatic hydrocarbons with CO_(2)

Despite the recent advances in the selective functionalization of C–C bonds in specific substrates,cleavage and functionalization of C–C bonds in acyclic substrates,such as ethane derivatives,remains challenging.In contrast to the well-developed functionalization of one carbon fragment after C–C bond cleavage,herein,we report a novel electro-reductive carboxylation of C(sp^(3))–C(sp^(3))bond in multi-aryl ethanes with carbon dioxide(CO_(2))by utilizing both carbon fragments.Thus,this reaction exhibits an atom-,step-economic approach for the synthesis of carboxylic acids,fulfilling principal aspirations of organic synthesis.Moreover,this method features mild reaction conditions,broad substrate scope,and good functional group tolerance.Symmetric and asymmetric substrates bearing primary,secondary,or tertiary C(sp^(3))–C(sp^(3))bonds are all amenable to this strategy,enabling one or two structurally different carboxylic acids to be facilely constructed at the same time.Mechanistic investigations indicate that carbanions might be the key intermediates in this reaction,which could be captured by CO_(2)efficiently.

Photocatalytic conversion of waste plastics to low carbon number organic products

As a great threat to all livings on earth,waste artificial plastics now are everywhere,from oceans to our cells[1].The world cannot withstand the growing waste plastic in million tonnes every year,which has already caused environmental pollution and economic losses[2].Besides the efforts for preparing novel plastics with the self‐decomposition ability,methods are needed to clear away these waste plastics leftover from history or recycle well this organic carbon resource[3].Photocatalysis is a potential solution for the conversion of waste plastics under mild conditions.In this perspective,we highlight the effect of photocatalytic approaches toward the generation of low carbon number organic products(C_(n) products,n≤8)from waste plastics,which can proceed under an inert or aerobic atmosphere.Notably,critical analysis of the carbon source in products is necessary to reveal the active species for the C–X bonds(X=C,N,and O)cleavage of plastics.Finally,we outline potential avenues for further development of this emerging field to enhance the yield of C_(n)(n≤8)products from waste plastics.

Syntheses,Characterization and Crystal Structures of Dithiocarbamate-based Mononuclear Palladium(Ⅱ) Complexes

By employing the dithiocarbamate salt （K（PPDC）, where PPDC = 4？-pyridyl-1-pipe-razine-4-dithiocarbamate） as the functional ligand and di-palladium complexes [（N^N）2Pd2（NO3ˉ）2]（NO3ˉ）2 （N^N = 2,2＇-bipyridine, bpy; 4,4＇-dimethylbipyridine, dmbpy） as corner, two novel single metal complexes with Pd（II） centers have been obtained. These organic-metal complexes were characterized by NMR, ESI-MS, elemental analysis, Uv-vis spectra and single-crystal X-ray diffraction analysis. Compound 1？（PF6）2 （[（bpy）Pd（PPDC）]·（PF6）2） crystallizes in triclinic, space group P , a = 8.3968（5）, b = 11.5565（7）, c = 18.2234（11）, α = 97.505（1）, β = 91.424（1）, γ = 106.146（1）o, C22H24N6S2P2F12Pd, Mr = 832.93, V = 1680.58（18） ？3, Z = 2, Dc = 1.646 Mg/m3, μ（MoKα） = 0.863 mm-1, F（000） = 828, the final R = 0.0455 and wR = 0.1390 for 6981 observed reflections with I 〉 2σ（I）. Similarly, compound 2？（PF6）2 （[（dmbpy）Pd（PPDC）]·（PF6）2） also crystallizes in triclinic, space group P , a = 13.9467（3）, b = 14.8390（2）, c = 17.0632（3） ？, α = 81.8680（10）, β = 87.051（2）, γ = 83.4590（10）o, C22H25N5S2P2F12Pd, Mr = 819.93, V = 3470.81（11） ？3, Z = 4, Dc = 1.569 Mg/m3, μ（CuKα） = 7.115 mm-1, F（000） = 1632, the final R = 0.0606 and wR = 0.1637 for 12835 observed reflections with I 〉 2σ（I）. Crystallography reveals that each metal center coordinates with two N atoms from bpy and two S atoms from PPDC in the square coordination mode. In the crystal structure of complex 1, a weak Pd……Pd interaction can be observed. Interestingly, it was also found that the mononuclear moieties of complex 2 could be packed into a 3-D porous framework via multiple intermolecular C–F……H hydrogen-boding interactions which extended in the a, b, and c axes with PF6ˉ anions frozen inside.

Redox-neutral photocatalytic strategy for selective C–C bond cleavage of lignin and lignin models via PCET process

It remains challenging to achieve the selective cleavage of C–C bonds in lignin or lignin model compounds to produce aromatic products in high yield and selectivity.We have developed a redox-neutral photocatalytic strategy to accomplish this goal in both b-O-4 and b-1 lignin models at room temperature(RT)via proton-coupled electron transfer(PCET)process without any pretreatments of substrate,by adjusting the alkalinity of base to obtain a lignin models/base PCET pair with a bond dissociation free energy close to 102 kcal/mol.Without breaking down C_b–Ccbond and any C–O bonds,this PCET method is 100%atom economy and produces exclusive Ca–C_bbond cleavage products,such as benzaldehydes(up to 97%)and phenyl ethers(up to 96%),in high to excellent yields and selectivities.Preliminary studies indicated that the PCET strategy is also effective for the depolymerization of native lignin at RT,thus providing significantly important foundation to the depolymerization of lignin.

Recent advances for the photoinduced C—C bond cleavage of cycloketone oximes

Nitriles are widely existed in many bioactive compounds,and they can be easily transformed into other functional groups.Therefore,the synthesis of nitriles under cyanide-free conditions is of significant importance.Recent advances for the synthesis of nitriles through photoinduced C—C bond cleavage of cycloketone oximes classified by the type of C—X bond forming are summarized.Various compounds possessing nitriles can be efficiently accessed via this method.