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    Home > Zhao Xin, research group of Shanghai Institute of organic science, Chinese Academy of Sciences: covalent organic framework based on acetamide linkage

    Zhao Xin, research group of Shanghai Institute of organic science, Chinese Academy of Sciences: covalent organic framework based on acetamide linkage

    • Last Update: 2019-11-11
    • Source: Internet
    • Author: User
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    COFS is a kind of crystalline organic porous polymer, which is formed by the covalent bond of organic monomers It has a highly regular framework structure Because of its porous, high specific surface area, structural unit diversity and other characteristics, C of S has been widely used in adsorption, separation, catalysis, sensing, photoelectric materials and so on Since 2005, Professor O.M Yaghi reported the first case of ofcof, the connection mode of COFS has gradually developed from early B-O, C = n to C = C, C-N, C-O, C-C and even mechanical interlock Different connection modes give different properties to ofcofs, and the development of new connection mode has become one of the main driving forces pushing the development of this field Recently, Zhao Xin research group of Shanghai Institute of organic chemistry, Chinese Academy of Sciences has made a breakthrough in the development of new connection mode of COFS, and relevant achievements have been published on J am Chem SOC (DOI: 10.1021 / JACS 9b08017) Zhao Xin research group Zhao Xin research group was founded in May 2008 At present, it is affiliated to the Key Laboratory of organic functional molecular synthesis and assembly chemistry, Chinese Academy of Sciences, Shanghai Institute of organic sciences There are 12 graduate students in the research group The research direction is organic functional materials and supramolecular chemistry In recent years, it mainly focuses on crystalline state /The creation, properties and applications of soluble two-dimensional organic porous polymers include COFS and SOFS Zhao Xin, researcher of Shanghai Institute of organic chemistry, Chinese Academy of Sciences He graduated from the Department of chemistry of Beijing Normal University in 1994, and obtained his Ph.D from Shanghai Institute of organic Science in 2003 (Tutor: academician Jiang Xikui, researcher Li zhanting) Later, he engaged in postdoctoral research in the Department of chemistry and chemical biology of Harvard University and the Department of chemistry of the University of Chicago In 2008, he set up a research group in Shanghai Institute of organic science and technology, and successively served as an associate researcher and researcher of innovation posts In 2010, he was selected into the "Pujiang talent plan" of Shanghai, won the National Science Fund for Distinguished Young Scholars in 2017, and selected as the outstanding academic leader of Shanghai in 2019 Frontier research achievements: as a reaction similar to the formation of imine bond, the formation of covalent organic framework acetaldehyde amine based on acetaldehyde amine linkage can be seen as a product of the formation of imine bond between aldehyde and amine and the attack of imine bond by another amine, which also has good reversibility The imine based connection is widely used in the construction of COFS, however, the acetaldehyde amine connection is only found in the preparation of a few amorphous porous polymers Before and after the reaction of acetaldehyde amines, SP 2-hybridized planar carbonyl carbon becomes sp 3-hybridized tetrahedral acetaldehyde amines carbon The great change of its configuration reduces the structure controllability of the polymer, and increases the difficulty of monomer design and C of s synthesis In addition, the monomer should not only adapt to the change of the stereostructure before and after the reaction, but also ensure that the reaction does not stay in the imine stage Two kinds of tetraaldehyde monomers (a 1 and a 2) with non planar D 2H symmetry were synthesized Their non planar structures can adapt to the changes of stereostructure before and after acetal amine formation Secondly, piperazine, a secondary amine, was selected as amine monomer to prevent the reaction from staying in the imine stage Through the combination of the two, they successfully obtained the first case of C of S (aminal-cof-1 and aminal-cof-1) connected by acetaldehyde amine The two kinds of two-dimensional acetal amines C of s were obtained by condensation of piperazine with tetraaldehyde monomers a 1 and a 2 under solvothermal conditions (Fig 1), respectively, with high crystallinity The structure of acetaldehyde amine C of S was proved by FT-IR, 13C and 15N CP / MAS NMR, XPS, PXRD, pore size distribution analysis and hydrolysis experiments (Fig 2 and Fig 3) Due to the symmetry of monomer and the particularity of connection mode, these two kinds of CFS are composed of alternating periodic distribution of Pentagon and hexagon holes in two-dimensional plane, which is a new topological structure of COF s CPI grid Figure 1 Schematic diagram of model reaction and synthesis of acetaldehyde amine COFS (source: J am Chem SOC.) Figure 2 Structural analysis of acetaldehyde amine COFS: (a) PXRD diagram of aminal COFS, experimental results (black) and refined results (red) (b) Differences between experimental and refined data in PXRD (c) The simulated PXRD of overlapping structure and (d) interleaving structure Schematic diagram of (E) overlapping accumulation and (f) staggered accumulation structure of aminal COF s (source: J am Chem SOC.) Fig 3 (a) N 2 adsorption desorption isotherms (77 K) of aminal-cof-1 and (c) aminal-cof-2, and (b) pore size distribution curves of aminal-cof-1 and (d) aminal-cof-2 (source: J am Chem SOC.) solid-state fluorescence test shows that the emission wavelength of monomer and corresponding coof is almost the same, indicating that the luminescent properties of monomer are not changed due to the formation of coos (Fig 4) This phenomenon can be attributed to two aspects: first, different from the usual two-dimensional C of S, the piperazine unit takes the chair conformation with lower energy in the two acetaldehyde amine C of S, on the other hand, the acetaldehyde amine unit has the tetrahedral configuration, which results in the larger inner layer spacing of acetaldehyde amine C of S The distance of benzene ring between the middle and layer of COFS is more than 6.0 Å, which exceeds the distance of Typical Aromatic accumulation and greatly reduces the interaction between layers Secondly, acetaldehyde amine is the structure of saturated bond, which makes the COFS conjugated in two-dimensional direction not extend This special structure of nonconjugation and nonplanarity makes the interaction between monomer primitives small after the formation of C of S, which is beneficial to retain the properties of monomer This study provides a new idea for the development of functional materials based on COF structure Through acetal amine, a special connection, the properties of C of S can be more accurately predicted and regulated by the retention of monomer properties Figure 4 Normalized solid-state fluorescence spectra of monomers and COFS (source: J am Chem SOC.) was recently published on J am Chem SOC 2019, 141, 14981-14986 The first author is graduate student Jiang Shuyan and Gan Shixian, and the corresponding author is researcher Zhao Xin The research was supported by NSFC, Shanghai Science and Technology Commission and Chinese Academy of Sciences 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 website, chembeangoapp, chembeango official micro blog, CBG information wechat subscription number and other platforms jointly launch the column of "people and scientific research", approach the representative research groups in China, pay attention to their research, listen to their stories, record their demeanor, and explore their scientific research spirit.
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