Angelw's "double yellow eggs": Professor Lei Shengbin's group and Professor Cu boulder's Zhang Wei's group develop the surface limited olefin metathesis reaction and product separation method

Introduction dynamic covalent chemistry (DCVC) mainly involves some reversible covalent reactions (such as Schiff base reaction, boric acid self condensation, boric acid esterification, olefin and alkyne decomposition reaction, etc.), in which the lowest energy product can be obtained through free exchange of molecular components Recently, Professor Lei Shengbin and Professor Zhang Wei from the University of Colorado Boulder (Cu boulder) of the United States have combined to work on the influence of reaction temperature, substituents and environmental pressure on the product distribution of surface limited olefin metathesis (DOI: 10.1002 / anie 201711040) and 2D on the surface COF was used to separate macrocycles and linear by-products in olefin metathesis (DOI: 10.1002 / anie 201803937) Introduction to Professor Lei Shengbin, professor and doctoral supervisor of School of science, Tianjin University It is mainly engaged in the design, assembly and characterization of interface supramolecular structure With scanning probe microscopy combined with density functional theory, molecular mechanics and Monte Carlo simulation as the main research means, it has made remarkable progress in the design and characterization of interface complex multi-component assembly structure, two-dimensional host guest structure, interface phase behavior and fine structure of conjugated polymer At present, he has published more than one hundred papers included in SCI in the authoritative magazines such as angel Chem Int ed., J am Chem SOC., nano lett., adv mater., ACS Nano, chem Mater., chem Comm., chem EUR J., etc., which have been cited more than 3000 times, and his personal H factor is 28 Write three reviews for topics in current chemistry, chem SOC Rev., angel Chem Int ed In 2005, he won the youth Chemistry Award of China Chemical Society, and in 2009, he was supported by the New Century Excellent Talents Program of the Ministry of education As reviewer of nanoscale, chem EUR J., chem Comm., Langmuir, polymer, soft matter, ChemPhysChem, SCI Chinachem And reviewer of the research foundation Flanders in Belgium Introduction to Professor Zhang Wei, Professor of Department of chemistry and biochemistry, University of Colorado Boulder, doctoral supervisor, member of American Chemical Society, visiting professor of eth, Zurich, Switzerland The main research fields are dynamic covalent chemistry, organic nanotechnology, material chemistry, renewable energy, etc In acc chem Res., chem SOC Rev., adv mater., J am Chem SOC, More than 50 SCI papers have been published in international famous academic journals, such as angelw Chem Int ed., etc., which have been cited more than 2000 times and have a wide international influence Therefore, they have been invited to make special reports at more than 10 academic conferences, such as the Pan Pacific Chemical Society, the annual meeting of the International Federation of theoretical and applied chemistry He has successively undertaken 6 NSFC projects, 2 DOD projects and 1 US oil research fund project He has successively won a series of scientific research awards, such as the Alfred P Sloan follow, provost achievement award, CAPA Outstanding Youth Award, 3M young professor award, American Natural Science Foundation career development award, University of Colorado innovation technology award and young professor career development award, and has been awarded six American invention patents One of the most important characteristics of DCVC is its response to external stimuli (such as temperature, light, electricity, mechanical stress, metal ions, protons, solvents, etc.), which can generate complex and special dynamic combinatorial library (DCL) Since the patterned monolayer has attracted much attention in the development of various nanotechnology, it is of great significance to study the response of DCL to the surface In this study, 1,3-divinyl6-decylbenzene (Fig 1, M1) and 1 were used, 3-divinyl6-decylbenzoate (Fig 1, M2) is the precursor molecule of the reaction The effects of reaction temperature, substituents and environmental pressure on the product distribution of olefin metathesis on the surface of high directional pyrolytic graphite (HOPG) were studied by using scanning tunneling microscopy (STM) The olefin metathesis reaction can be carried out at the same time in the solution phase and at the interface It can be formed either by the cyclization of linear hexamer (Fig 1, path I) or by the disconnection of longer linear polymer (Fig 1, path II) Fig 1 1,3-divinyl6-decylbenzene (M1) and 1, The results of the non periodic olefin metathesis of 3-divinyl6-decylbenzoate (M2) (source: angel Chem Int ed doi: 10.1002 / anie 201711040) show that the length of the molecular chain will increase with the increase of the reaction temperature, and finally the most stable hexameric ring will be formed The adsorption and assembly of monomers and intermediates on the HOPG surface will greatly reduce the translation and free rotation ability of the adsorbed products, thus greatly changing the product distribution in the dynamic reaction system If one of the products can form a stable assembly structure on the surface of HOPG under a certain reaction condition, it shows that the product has a strong affinity on the surface of HOPG, which leads to the amplification of the product on the surface Therefore, the selective adsorption of products on the surface can make a specific product be amplified, and specific intermediate products, such as dimers, can be obtained by using the surface confinement The structural changes of the dynamic olefin metathesis reaction system were observed directly on the HOPG surface by STM, which provided direct evidence for the reaction mechanism of olefin metathesis This surface limited dynamic covalent system provides an interesting new method for the development of surface supported molecular assembly and grid structure This achievement was recently published in angelwandtechemie International Edition The title of the paper is "surface agreed dynamic value system driven by olefin thesis" The authors are Chunhua Liu, eunsol Park, Yinghua Jin, Jie Liu, Yanxia Yu, Weizhang *, Shengbin Lei *, Wenping Hu (angel Chem Int ed., 2018, 57, 1869-1873, DOI: 10.1002/anie.201711040) The surface Schiff base COF is used to separate the aromatic vinylidene macrocyclic vinylidene macrocyclic (AVMs) which is a kind of hydrocarbon with rigid conjugated skeleton and connected by ­­­­­­­­­­‐ C = C - Because of its potential application value in many fields, it has attracted scientists' extensive interest in recent years The most stable target macrocycles can be prepared by one pot method Under the condition of long-life and high activity catalyst, suitable reaction temperature and reaction time, the olefin double decomposition reaction can reach the reaction equilibrium and get the main target product closed macrocycle At the same time, the reaction will inevitably produce some linear by-products with different degrees of polymerization Their chemical structure formula is shown in Fig 2 (a, b) Because linear by-products and macrocyclic compounds have very similar structure and polarity, it is difficult to separate them by traditional separation methods such as silica gel column chromatography, recrystallization and so on Therefore, it is necessary to find a new method to separate large rings from linear by-products The covalently connected 2D COF has a stable structure framework and periodic nanopores With the help of the weak noncovalent force (such as van der Waals force, weak hydrogen bond, etc.) between the two-dimensional grid and the object, a stable two-dimensional host guest structure can be constructed to realize the combination and separation of specific object molecules Fig 2 a) synthesis of arylene vinylidene macrocyclic (AVMs) compounds by olefin metathesis; b) chemical formula of AVMs; c) 4,4 '- diaminoazobenzene (DA) and 1,3, 5-benzenetrialdehyde (BTA) reacts to produce 2D COF on hexagon surface (source: angel Chem Int ed doi: 10.1002 / anie 201803937) In the study, the author carefully designed a kind of surface COF of Schiff base whose pore diameter can match the rigid diameter of the large ring (Figure 2C) This structure can form the maximum interaction force with the large ring, forcing the large ring to occupy the pores of the surface COF preferentially to form a relatively stable host guest system, while the linear by-products can only be adsorbed on the upper layer of the host guest structure Subsequently, the linear by-products can be easily removed by solvent cleaning to further purify the macrocycle The results show that the linear by-products adsorbed on the host and guest can be cleaned by octanoic acid smoothly As shown in Figure 3, due to the hydrogen bond between the macrocycle and the surface COF, the macrocycle compounds are well adsorbed in the surface COF pores Finally, the host guest system of the macrocycle and the surface COF is cleaned with 1,2,4-trichlorobenzene (TCB), which has better solubility The macrocycle can be released from the surface COF to separate the macrocycle and the linear polymer An important advantage of this kind of surface purification is that the separation process can be carried out step by step, which provides a new way for the separation and purification of cyclic products of olefin metathesis Fig 3 separation of AVM2 and linear by-products by using the force between surface cofdb and guest molecules: a) schematic diagram of separation process; b) pre prepared surface cofdb, I set = 30 PA, V bias = 600mV; c) adding AVM2; d) after octanoic acid cleaning; E) after TCB cleaning C-E: I set = 50 PA, V bias = 860 MV (source: angelw Chem Int ed doi: 10.1002/anie.201803937) This achievement was recently published in angelwandtechemie International Edition The title of the paper is "separation of arynevinylene macrocycles with a surface confinedtwo dimensional imine covalent organic framework" The authors are Chunhua Liu, eunsol Park, Yinghua Jin, Jie Liu, Yanxia Yu, Weizhang *, Shengbin Lei *, Wenping Hu (angel Chem Int ed 2018, DOI: 10.1002/anie.201803937) The first author of the above two research results is Professor Lei Shengbin's doctoral student Liu Chunhua in Harbin University of technology, and the corresponding authors are professor Lei Shengbin and Professor Zhang Wei The work was supported by funds from the National Natural Science Foundation, the Ministry of science and technology, the University of Colorado Boulder Education Fund and Hong Kong Wang Kuancheng Education Fund Nowadays, people and scientific research have been paid more and more attention in the economic life China has ushered in the "node of science and technology explosion" Behind the progress of science and technology is the work of countless scientists In the field of chemistry, in the context of the pursuit of innovation driven, international cooperation has been strengthened, the influence of Returned Scholars in the field of R & D has become increasingly prominent, and many excellent research groups have emerged in China For this reason, CBG information adopts the 1 + X reporting mechanism CBG information, chembeangoapp, chembeango official microblog, CBG wechat subscription number and other platforms jointly launch the column of "people and scientific research", approach the domestic representative research group, pay attention to their research, listen to their stories, record their demeanor, and explore their scientific research spirit.