Intercalation assisted liquid phase production of disulfide zirconium nanosheets for efficient electrocatalytic dinitrogen reduction to ammonia

Disulfide zirconium(ZrS_(2)) is a two-dimensional(2D) transition metal disulfide and has given rise to extensive attention because of its distinctive electronic structure and properties.However,mass production of high quality of ZrS_(2)nanosheets to realize their practical application remains a challenge.Here,we have successfully exfoliated the bulk ZrS_(2)powder with the thickness of micron into single and few-layer nanosheets through liquid-phase exfoliation in N-methylpyrrolidone(NMP) assisted via aliphatic amines as intercalators.It is found that the exfoliation yield is as high as 27.3%,which is the record value for the exfoliation of ZrS_(2)nanosheets from bulk ZrS_(2)powder,and 77.1% of ZrS_(2)nanosheets are 2-3 layers.The molecular geometric size and aliphatic amine basicity have important impact on the exfoliation.Furthermore,the ZrS_(2)nanosheets have been used as catalyst in the electrocatalytic dinitrogen reduction with the NH3yield of 57.75 μg h^(-1)mg_(cat.)^(-1),which is twice that by ZrS_(2)nanofibers reported in literature and three times that by the bulk ZrS_(2)powder.Therefore,the liquid phase exfoliation strategy reported here has great potential in mass production of ZrS_(2)nanosheets for high activity electrocatalysis.

Activation of Dinitrogen by Gas-Phase Species

Reactions of gas-phase species with small molecules are being actively studied to understand the elementary steps and mechanistic details of related condensed-phase processes.Activation of the very inert N≡N triple bond of dinitrogen molecule by isolated gas-phase species has attracted considerable interest in the past few decades.Apart from molecular adsorption and dissociative adsorption,interesting processes such as C-N coupling and degenerate ligand exchange were discovered.The present review focuses on the recent progress on adsorption,activation,and functionalization of N2 by gas-phase species(particularly metal cluster ions)using mass spectrometry,infrared photo-dissociation spectroscopy,anion photoelectron spectroscopy,and quantum chemical calculations including density functional theory and high-level ab initio calculations.Recent advances including characterization of adsorption products,dependence of clusters’reactivity on their sizes and structures,and mechanisms of N≡N weakening and splitting have been emphasized and prospects have been discussed.

An Empirical Model for Dinitrogen Gas Emission from Inland Waters

The motivation to calculate this empirical model resulted from often observing—at the time disconcerting—excess dinitrogen gas (N2 concentration > background concentration) in bubble-gas emission samples, collected primarily for the purpose of carbon budget research, from Brazilian rivers and reservoirs sampled during roughly 100 field surveys lasting 4 days each on average and executed between years 2000 and 2012. We model the (serendipitously) measured dinitrogen gas above environmental concentration (N2aec) escaping in bubbles from Brazilian rivers as a function of dissolved nitrogen (N) in water. To this model, we mathematically add a pre-existing model of diffusively emitted denitrified dinitrogen (also as a function of dissolved N) from streams in the United States of America (USA). The resulting model predicts denitrified dinitrogen water-air emission from inland waters in the USA, China and Germany.

Ligand Effects in Dinitrogen Hydrogenation of Binuclear Zirconium Complexes

In this work, we report a theoretical exploration of the ground-state electronic structures and molecular vibrational properties of a series of binuclear zirconium complexes in the framework of density functional theory （DFT） employing the B3LYP hybrid functional. The calculated results reveal that the electronic structure of the complex [（η^5-C5Me5）2Zr]2（μ^2, η^2, η^2-N2） is unfavorable for hydrogenation due to the exclusion of side-on dinitrogen in the LUMO＋ 1 molecular orbital as compared with the reactant 1 [（η^5-C5Me4H）2Zr]2（μ2,η^2,η^2-N2）. Besides, the structural feature of the hypothetical intermediate 1′, [（η^5C5Me4H）2Zr]2（μ2,η^2, η^2-N2）-n2, clearly implies the possibility of further hydrogenation. In addition, the distinguishing of vibrational modes of experimental intermediate 2, [（η^5-C5Me4H）2ZrH]2（μ2,η^2,η^2-N2H2）, indicates that the asymmetric stretching of Zr-N and Zr-H leads to dissociation. Moreover, the vibrational intensity of Zr-H is stronger than that of Zr-N. Therefore, it can be predicted that excess hydrogen atmosphere is necessary to ensure the dissociation of Zr-N bonds.

Synthesis and Crystal Structure of a Ruthenium(Ⅱ) Compound of Dinitrogen

The title compound [Ru（bph）（PPh3）2（N2）]·（PF6）·1.5CH2Cl2 （bph = N-（benzoyl）- N＇-（picolinylidene）-hydrazine） has been prepared and characterized by X-ray diffraction analysis. It crystallizes in the monoclinic system, space group P21/n with a = 13.5201（6）, b = 15.5078（6）, c = 25.0656（13） A, β= 100.257（3）°, C50.50H43Cl3F6N5OP3Ru, Mr= 1150.23, V= 5171.4（4） A3, Z = 4, F（000） = 2332, Dc = 1.477 g/cm^3 and ,μ（MoKa） = 0.615 mm^-1. The structure was refined to R = 0.0524 and wR = 0.1398 for 8060 observed reflections （I 〉 2σ（I））. The Ru-N2 and N-N bond distances are 1.919（4） and 1.133（5）A, respectively.

Synthesis and reactivity of cobalt dinitrogen complex supported by nonsymmetrical pincer ligand

A nonsymmetrical PNN pincer ligand[6-(^(t)Bu_(2)PNH)C_(5)H_(4)N-2-(3-Mes)C_(3)H_(2)N_(2)]and its corresponding cobalt-N_(2)complex were synthesized and characterized.By the stoichiometric reaction of the PNN ligand lithium salt with CoCl_(2),the complex 3,(PNN)CoCl,was obtained.Then,reduction of 3 with NaBHEt3under a dinitrogen atmosphere yielded complex 5,(PNN)Co(Ⅰ)(η^(1)-N_(2)).Single-crystal X-ray analysis,IR spectrum,and DFT calculations revealed that the dinitrogen in 5 was only weakly reduced by the cobalt center.The reactions of 5 with carbon monoxide and 2,6-dimethylphenyl isocyanide gave carbonyl and isocyanide complexes 6 and 7 with the release of N_(2),respectively.Furthermore,these cobalt complexes,especially complex 5,demonstrated the capacity to convert dinitrogen to N(TMS)_(3)with moderate efficiency.

Light-Driven Dinitrogen Activation with Transition Metal Complexes:Mechanisms and Applications

Comprehensive Summary,The Haber-Bosch process,which is used for ammonia(NH3)synthesis,requires vast amounts of energy,accounting for approximately 1%—2%of the world's annual energy consumption.Therefore,researchers in both industry and academia are interested in developing sustainable and environmentally friendly methods for synthesizing nitrogenous compounds at ambient conditions using renewable energy sources such as visible light.While several examples of thermal activation of dinitrogen molecules have been demonstrated using various transition metals and ligand frameworks,the use of light to weaken or split the strong N—N bond has been less explored.This article presents an overview of molecular complexes capable of dinitrogen photocleavage and provides mechanistic insights into the photoactivation process through experimental and theoretical studies.We believe this review will provide readers with an in-depth understanding of the current state-of-the-art and future research perspectives,particularly in the use of visible light for dinitrogen activation and transformation.

One-Electron Reduction of Constrained and Unsymmetric Diiron Dinitrogen Complexes

Iron sites in both nitrogenase enzymes and chemical catalysts for N_(2) fixation are typically at constrained distances and angles.Herein,we report a one-electron reduction reaction realized by constrained diiron dinitrogen cores.Using the semicircular bis(β-diketiminate)ligand,a series of diiron dinitrogen complexes were synthesized,in which the N_(2) groups were allowed to bind with Fe-Ct_(N2)-Fe angles ranging from 154°to 158°(Ct_(N2)=centroid of N_(2)).One-electron reduction of complex 2a[LFe(μ-N_(2))Fe(Et_(2)O)]gave dimer product 3a[LFe(μ-N_(2))FeK]_(2)(μ-N_(2))or monomer 3b[LFe(μ-N_(2))Fe(DMAP)K].Based on superconducting quantum interference device measurements and density functional theory calculations,2a,3a,and 3b exhibited ground spin states of S=3,S=5,and S=5/2,respectively.In addition,complex 3 underwent N_(2)derivatization via a silylation pathway followed by an acidic cleavage to yield N_(2)H_(4)as the product.

Understanding reaction mechanisms of metal-free dinitrogen activation by methyleneboranes

Dinitrogen activation under mild conditions is important but extremely challenging due to the inert nature of the N≡N triple bond evidenced by high bond dissociation energy(945 k J/mol) and large HOMOLUMO gap(10.8 e V). In comparison with largely developed transition metal systems, the reported main group species on dinitrogen activation are rare. Here, we carry out density functional theory calculations on methyleneboranes to understand the reaction mechanisms of their dinitrogen activation. It is found that the methyleneboranes without any substituent at the boron atom performs best on dinitrogen activation, which could be contributed to its small singlet-triplet gap. In addition, strong correlations are achieved on dinitrogen activation between the singlet-triplet energy gap and the reaction energies for the formation of the end-on products as well as the side-on ones. The principal interacting orbital analysis suggests that methyleneboranes can mimic transition metals to cleave the N≡N triple bond. Our findings could be helpful for experimental chemists aiming at dinitrogen activation by main group species.

Synthesis and structural analysis of titanium-μ-dinitrogen complex supported by di-anionic guanidinate ligands

The synthesis,characterization,and theoretical studies of titanium-μ-N_(2) complexes with di-anionic guanidinate ligands were reported as the first example of its kind.Thus,with(Me_(3)Si)_(2)N-guanidinate ligands,the mono-anionic guanidinate-supported titanium-μ-N2complex 1 was obtained.Then,reduction of 1 with potassium afforded the di-anionic guanidinate-supported titanium-μ-N_(2) complex 2 via cleavage of one N–Si bond of the(Me3Si)2N substituents in 1,changing the guanidinate ligands automatically from mono-anionic to di-anionic and remarkably lengthening the bond length of theμ-N_(2).Characteristic studies and DFT calculations were performed to reveal that the di-anionic guanidinate ligands stabilized the geometry of 2 and increased the charge density on the bridging dinitrogen.

Dinitrogen Functionalization Affording Structurally Well-Defined Cobalt Diazenido Complexes

Cobalt-bis(dinitrogen)complexes[LCo(N_(2))_(2)]−(3,4)with simple and commercially available bidentate phosphine ligands(L:Cy_(2)PCH_(2)CH_(2)PCy_(2))were synthesized and structurally characterized.Further N2 functionalization by treating the complex 3b with i Pr_(3)SiCl afforded the first structurally characterized cobalt diazenido complex 5.These complexes 3–5 were found to be effective catalysts for the transformation of N2 into N(SiMe_(3))_(3).The electronic structure of the cobalt diazenido complex 5 is supported by quantum computational calculations based on stateof-the-art energy decomposition analysis(EDA)in conjunction with the natural orbitals for chemical valence(NOCV)method.

Recent Developments of Dinitrogen Activation on Metal Complexes and Clusters

Dinitrogen(N_(2)) is the major component of the atmosphere and many factors bring about dinitrogen inertness with low reactivity. Dinitrogen activation on metal complexes and clusters under ambient condition is the long-standing goal in the modern chemistry. In this review,an attempt has been made to survey the mechanistic aspects of dinitrogen activation and functionalization based on different coordination binding modes of dinitrogen. Our goal is to provide a comprehensive survey of dinitrogen activation in order to guide the relevant research in the future.

基于光腔衰荡光谱技术NO_(3)和N_(2)O_(5)在线测量系统的表征与应用

报道自主研发的基于光腔衰荡光谱技术的大气NO_(3)/N_(2)O_(5)在线测量系统及其参数表征结果。在时间分辨率为1min的情况下,NO_(3)和N_(2)O_(5)最低检测限分别为1.7×10^(-12)和2.9×10^(-12)。在采样流量6L/min和使用1天滤膜的情况下,利用标准源实验确定NO_(3)和N_(2)O_(5)的采样损耗分别为17.0%和18.0%。Allan方差分析结果表明,在60~100s积分条件下可获得较好的系统稳定性。在北京城区开展大气NO_(3)和N_(2)O_(5)观测,结果表明测量系统可以满足大气环境中NO_(3)及N_(2)O_(5)的高灵敏度测量。

Single-molecule imaging of dinitrogen molecule adsorption on individual iron phthalocyanine

Nitrogen fixation is a vital process for both nature and industry.Whereas the nitrogenase can reduce nitrogen in ambient environment in nature,the industrialized Haber-Bosch process is a high temperature and high-pressure process.Since the discovery of the first dinitrogen complex in 1965,many dinitrogen complexes are prepared in a homogeneous solution to mimic the nitrogenase enzyme in nature.However,studies of the heterogeneous process on surface are rarely addressed.Moreover,molecular scale characterization for such dinitrogen complex is lacking.Here,we present a simple model system to investigate,at the single-molecule level,the binding of dinitrogen on a surface confined iron phthalocyanine(FePc)monolayer through the combination of in-situ low-temperature scanning tunneling microscopy(LT-STM)and X-ray photoelectron spectroscopy(XPS)measurements.The iron center in FePc molecule deposited on Au(111)and highly oriented pyrolytic graphite(HOPG)surface can adsorb dinitrogen molecule at room temperature and low pressure.A comparative study reveals that the adsorption behaviors of FePc on these two different substrates are identical.Chemical bond is formed between the dinitrogen and the Fe atom in the FePc molecule,which greatly modifies the electronic structure of FePc.The bonding is reversible and can be manipulated by applying bias using a STM tip or by thermal annealing.

Dinitrogen Activation of Cyclopentadienyl-Phosphine–Iron Complexes of Three Different Valences

A series of structurally well-defined iron-dinitrogen complexes(LFe-N2)bearing cyclopentadienylphosphine ligands(L)were synthesized and analyzed by single-crystal X-ray structural analysis,IR/Raman spectra,magnetometry,Mössbauer spectroscopy,and elemental analysis.The conversion relationship and the change of the spin states among the iron complexes with different valences were studied in detail.

碳载金属单原子催化剂的电合成氨进展

氨不仅是生产农业肥料和医药分子的关键原料,同时因其具备高能量密度和零碳排放的特性,也被视为极具潜力的能源载体.鉴于当前对环保和可持续发展的迫切需求,实现氨分子的绿色合成已成为重要任务.其中,利用可再生能源驱动的电化学合成氨技术,因其对环境友好和高效性,被视为替代传统哈伯-博世工艺的绿色路径,具有广阔的应用前景.在电化学催化合成氨的研究中,单原子催化剂(SAC)因其独特的性质而备受关注.SAC的孤立金属中心不仅提高了金属原子的利用率,而且有效抑制了氮-氮偶联反应,从而显著提升了催化合成氨的效率,成为当前的研究热点.本文综述了SAC电催化合成氨领域的最新研究进展,旨在为科研工作者提供基础的理论和实验参考.系统总结了不同氮源(包括氮气、硝酸根、亚硝酸根及一氧化氮)合成氨的研究进展,并深入探讨了催化剂的理论和实验设计、催化活性中心的种类及其催化活性,以及真实反应过程中的催化动态行为.首先,介绍了自然和人工固氮系统中的氮循环路径.自然固氮系统展示了氮气、氮氧化物、氨的循环路径,为不同氮物种合成氨方法提供了可借鉴的思路;而人工氮循环则阐述了社会发展、工业生产对自然循环氮平衡的破坏,凸显了电化学人工固氮的必要性.随后,基于理论模拟方法,在原子和分子尺度上总结了不同氮物种在催化剂表面的反应过程.例如,在氮气合成氨过程中探讨了涉及的解离路径、交替缔合及远端缔合路径等.本文详细阐述了催化活性结构的理论筛选方法的重要性,并介绍了如何通过结构稳定性评估、反应物种的吸附活性以及催化活性及选择性的综合考量,来确定最佳的催化活性中心种类及微观结构.随后,总结了科研人员基于理论筛选结果,采用热解策略制备碳载金属SAC的研究进展.这些策略包括,碳基底与金属络合物的混合热解策略、金属有机框架衍生策略、金属辅助小分子热解策略、吸附活性策略及模板牺牲辅助策略等.同时,系统地总结了不同SAC对四种氮前驱体还原反应的催化活性.此外,深入地讨论了催化活性中心如Cu和Fe单原子在合成氨反应过程中的结构动态演化行为,强调了非原位结构可能仅是单原子前驱体,而反应过程中演变结构才是真实催化活性中心.这对于深入理解SAC电催化合成氨的机理和提高催化效率有一定的借鉴意义.最后,本文简要探讨了单原子催化剂在合成氨领域所面临的挑战及发展机遇.主要包括(1)发展更为精准的理论预测方法,实现从静态计算向动态模拟的转变,以更准确地预测和解析催化剂在实际反应中的行为机制;(2)积极发展多原子协同位点,从金属单原子到双甚至三原子团簇,利用多原子间的协同作用提升催化效率;(3)发展可替代氨合成路径,如低温等离子体耦合电化学合成氨技术,以推动氨合成技术的绿色化和高效化;(4)结合动态谱学技术的发展及应用,通过在原位甚至工况条件下的探究,深入解析动态反应过程,为催化剂的进一步优化提供科学依据.通过发展更为精准的理论预测方法、多原子协同位点、可替代氨合成路径以及结合动态谱学技术的进步,我们有望推动单原子催化剂在合成氨领域的应用取得更大突破.

N_2O_5硝解DPT制备HMX

为了获得绿色硝化DPT制备HMX的工艺,研究了N2O5/HNO3和N2O5/有机溶剂两种硝化体系硝解DPT。在N2O5/有机溶剂体系中考察了不同溶剂对DPT的硝解,主要生成了低熔点的副产物,只有极少量的HMX生成,N2O5/有机溶剂体系不适合硝解DPT制备HMX。在N2O5/HNO3体系中硝解DPT,考察了反应时间、反应温度、硝酸铵用量、反应料比等对HMX收率的影响。结果表明,随着N2O5用量的增加,HMX的收率呈现先增加后降低,在N2O5与DPT物质的量比为2、HNO3与DPT的物质的量比为36、反应时间30min、反应温度25℃的条件下,HMX收率可达58%,纯度99%,得出在N2O5/HNO3体系中硝解DPT能以较高收率制备HMX。

FeZSM-5/N_2O催化氧化苯制苯酚

苯一步氧化制苯酚 ,是有机物氧化合成中富有挑战性的研究课题之一。该文着重论述了在Fe ZSM- 5及其一系列沸石催化剂上 ,应用氧化亚氮作为氧化剂使苯直接氧化制苯酚的研究进展。这一系列催化剂体系的特殊之处在于通过氧化亚氮在沸石分子筛上的分解获得具有催化活性的 α-氧。详细讨论了在沸石分子筛上形成特殊结构的铁氧化物作为催化活性中心这一观点。由于这种催化体系对苯直接氧化制苯酚的反应有着很高的选择性 ,因此 。

硝酸酯的绿色合成

评述了N2O5为硝化剂制备硝酸酯类含能材料的绿色合成技术,分析了N2O5-有机溶剂硝化、N2O5-固体载体硝化和引入保护基硝化等三种体系工艺的过程和特点,展望了各硝化体系的发展前景。并以N2O5为硝化剂考察了环氧丙烷类化合物开环硝化过程,探讨了取代基的电子效应和立体效应对环氧丙烷类化合物开环硝化过程的影响规律。

绿色硝化技术合成HMX的小试工艺研究

报道了以 DADN(1,5 -二乙酰基 - 3,7-二硝基 - 1,3,5 ,7-四氮杂环辛烷 )为原料在新型硝化剂 N2 O5- HNO3溶液中合成 HMX的方法 ,HMX的得率在 96 %以上 ,熔点 2 72 .0～ 2 72 .8℃。此外 ,对影响 HMX得率的几种因素作了初步分析。