2972-83-0Relevant articles and documents
Hierarchical Micro- and Mesoporous Zn-Based Metal–Organic Frameworks Templated by Hydrogels: Their Use for Enzyme Immobilization and Catalysis of Knoevenagel Reaction
Cheng, Kaipeng,Svec, Frantisek,Lv, Yongqin,Tan, Tianwei
, (2019)
Encapsulation of enzymes in metal–organic frameworks (MOFs) is often obstructed by the small size of the orifices typical of most reported MOFs, which prevent the passage of larger-size enzymes. Here, the preparation of hierarchical micro- and mesoporous
The Photophysics of Three Naphthylmethylene Malononitriles
Breffke, Jens,Williams, Brian W.,Maroncelli, Mark
, p. 9254 - 9267 (2015)
The solvent dependence of the photophysical properties of three naphthylmethylene malononitriles, 1-(1-naphthalenylmethylene)-propanedinitrile (1-MN), 2-(2-naphthalenylmethylene)-propanedinitrile (2-MN), and 2-(3,4-dihydro-1(2H)-phenanthrenylidene)-propanedinitile (r2-MN), was studied in order to determine their potential utility as fluidity probes and to make comparisons to the better studied benzylidene malononitriles. Density functional calculations were used to understand the possible conformational states related to rotation about the vinyl-aromatic bond ("τ"). Absorption and emission frequencies, extinction coefficients, fluorescence quantum yields, and fluorescence lifetimes were measured in 11 representative solvents. Both the computational and experimental results indicate that the S0 → S1 transitions of these molecules have substantial charge-transfer character and produce highly polar excited states. Emission appears to result from relaxed S1 states which do not differ qualitatively from the Franck-Condon states reached by absorption. In 2-MN, time-resolved emission reveals the presence of two ground-state conformers ("a" and "b" differing by ～180 rotation about τ) coexisting in low-polarity solvents. In contrast, 1-MN appears to exist primarily as a single dominant ground-state conformer. Fluorescence lifetimes vary from ～1 ps in 1-MN to ～200 ps in 2-MN(a) at room temperature. With the exception of 2-MN(a), the lifetimes vary systematically with solvent in a manner similar to what is observed in the benzylidene malononitriles. Both solvent polarity and fluidity appear to be important determinants of lifetime. The primary mechanism of fluorescence decay in naphthylmethylene malononitriles is likely to be the same as that of the benzylidene malononitriles - twisting about the double bond in S1, which leads to rapid internal conversion via a conical intersection with S0. (Graph Presented).
A green synthesis of a simple chemosensor that could instantly detect cyanide with high selectivity in aqueous solution
Lin, Qi,Chen, Pei,Fu, Yong-Peng,Zhang, You-Ming,Shi, Bing-Bing,Zhang, Peng,Wei, Tai-Bao
, p. 699 - 702 (2013)
A novel and simple cyanide chemosensor 2-(naphthalen-1-ylmethylene) malononitrile (L) was designed and synthesized via a green chemistry method in water without using any catalyst. The chemosensor showed an excellent sensitivity and selectivity for CN- in aqueous solution. The detection limit could be as low as 1.6 × 10-7 mol/L (0.16 μmol/L), which is far lower than the WHO guideline of 1.9 μmol/L cyanide for drink water.
Direct fabrication of strong basic sites on ordered nanoporous materials: Exploring the possibility of metal-organic frameworks
Liu, Wei,Zhu, Li,Jiang, Yao,Liu, Xiao-Qin,Sun, Lin-Bing
, p. 1686 - 1694 (2018)
Heterogeneous strong base catalysts possessing ordered nanoporous structure are highly expected due to their high activity and shape selectivity in diverse reactions. However, their fabrication remains a great challenge because quite high temperatures (600-700 °C) are compulsory for the generation of strong basicity on conventional ordered nanoporous materials (i.e., zeolites and mesoporous silicas). Here, we report for the first time direct fabrication of strong basic sites on metal-organic frameworks (MOFs) by using guest-host redox (GHR) interaction between base precursors and low-valence metal centers (e.g., Cr3+), which breaks the tradition of thermo-induced decomposition of base precursors. It is fascinating that base precursor KNO3 can be converted to strong basic species on MIL-53(Cr) at 300 °C, which is much lower than that on zeolite Y (700 °C) and mesoporous silica SBA-15 (600 °C). The resultant solid base exhibits strong basicity, ordered nanoporous structure, and high activity and shape selectivity in base-catalyzed reactions.
Halloysite nanotubes (HNTs)@ZIF-67 composites - A new type of heterogeneous catalyst for the Knoevenagel condensation reaction
Hou, Buwei,Wu, Jie
, p. 17621 - 17628 (2020)
Composite materials based on metal-organic frameworks (MOFs) have shown outstanding performance due to their high porosity, molecular-level characterization, and structural and functional tunability. In this article, we develop a new type of composite material - HNTs@ZIF-67 - by the in situ growth of ZIF-67 nanoparticles (NPs) on halloysite nanotubes (HNTs), which were characterized by SEM, TEM, PXRD, FT-IR, TGA, XPS and N2 adsorption-desorption isotherms. The results clearly indicate that HNTs were wrapped in the ZIF-67 shell with a thickness of 50 nm which is much smaller than the 500 nm size of the as-synthesized ZIF-67. The nano-sized HNTs@ZIF-67 can effectively catalyze the Knoevenagel condensation reaction of larger conjugated/heterocyclic aromatic formaldehydes with malononitrile. The catalytic activities with >99% yields for the reaction of 4-pyridinecarboxaldehyde with malononitrile were maintained even after three cycles, and the composite still retained the original structure and morphology. This journal is
A novel adenine-based zinc(II) metal-organic framework featuring the Lewis basic sites for heterogeneous catalysis
Zhang, Shixing,He, Hongming,Sun, Fuxing,Zhao, Nian,Du, Jianshi,Pan, Qinhe,Zhu, Guangshan
, p. 55 - 59 (2017)
Metal-organic frameworks (MOFs), as a new sort of crystalline materials, have attracted lots of interest in many applications during the past decades. Recently, many efforts have been focused on the development of MOFs as heterogeneous catalysis. In this
Impact of an aryl bulky group on a one-pot reaction of aldehyde with malononitrile and: N-substituted 2-cyanoacetamide
Vala, Ruturajsinh M.,Patel, Divyang M.,Sharma, Mayank G.,Patel, Hitendra M.
, p. 28886 - 28893 (2019)
In this study, we successfully explored the effect of steric hindrance on the one-pot reaction of different aryl aldehydes with malononitrile and N-substituted 2-cyanoacetamide in the presence of piperidinium acetate as the catalyst. It involved the Knoevenagel condensation of the aldehyde and malononitrile to produce arylidene malononitrile as an intermediate, which was further treated with N-substituted 2-cyanoacetamide to give 6-Amino-2-pyridone-3,5-dicarbonitrile derivatives when the less steric bulky group was involved. High steric hindrance changed the earlier reaction route and gave N-substituted 2-cyanoacrylamides via a slower route.
Bifunctional design of stable metal-organic framework bearing triazole–carboxylate mixed ligand: Highly efficient heterogeneous catalyst for knoevenagel condensation reaction under mild conditions
Kumar, Sandeep,Li, Shuangshuang,Liu, Feixiong,Ren, Peng,You, Hengzhi,Zhao, Limin
, (2020)
A highly water stable zinc metal–organic framework (ZnMOF), {[Zn(HL)2]}n, was synthesized using a triazole–carboxylate-based mixed ligand (L = 5-(4H-1,2,4-triazol-4-yl)isophthalic acid). A 2D MOF was formed by hydrothermal synthesis, and extended to a 3D supramolecular network through strong hydrogen bonding. This MOF was fully characterized by Fourier-transformation infrared spectroscopy, thermogravimetric analysis, single-crystal X-ray diffraction (XRD), powder XRD and elemental analysis. Owing to the d10 configuration of this ZnMOF, its luminescent properties were suitable for the sensing of the CN? ions over other anions, as inferred from the florescence result. However, regarding the catalytic mechanism, this ZnMOF showed a strong ability to react with CN?, which might be due to the hydrogen bonding between the COOH groups without coordination. This interaction behavior with CN? ions makes the ZnMOF a promising heterogeneous catalyst for Knoevenagel condensations using malononitrile and aldehyde derivatives as reactants under mild conditions. All reactions were conducted in water as a green solvent.
Function-Structure Relationship in Metal-Organic Frameworks for Mild, Green, and Fast Catalytic C-C Bond Formation
Razavi, Sayed Ali Akbar,Morsali, Ali
, p. 14429 - 14439 (2019)
Tunability in chemical functionality is a promising characteristic of metal-organic frameworks (MOFs), which plays an important role in developing and improving the practical applications of MOFs. Here, we applied this important feature of MOFs to be in line with sustainable development and green chemistry principles through the synthesis of MOF-based heterogeneous organocatalysts. According to our green functionalization strategy, some isostructural MOFs (azine decorated TMU-4 with the formula [Zn(OBA)(BPDB)0.5]n·2DMF, azine-methyl functionalized TMU-5 with the formula [Zn(OBA)(BPDH)0.5]n·1.5DMF, dihydro-tetrazine decorated TMU-34 with the formula [Zn(OBA)(H2DPT)0.5]n·DMF, and tetrazine functionalized TMU-34(-2H) with the formula [Zn(OBA)(DPT)0.5]n·DMF, where H2OBA = 4,4′-oxybis(benzoic acid), BPDB = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene, BPDH = 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene, H2DPT = 3,6-di(pyridin-4-yl)-1,4-dihydro-1,2,4,5-tetrazine, and DPT = 3,6-di(pyridin-4-yl)-1,2,4,5-tetrazine) have been applied for mild, green, and fast Knoevenagel condensation. These frameworks display different Lewis basic catalytic activities owing to their different functionality and function accessibility. Contrary to extensive articles published about Knoevenagel condensation, this study involves the rare examples in Knoevenagel condensation with such mild conditions (room temperature and atmospheric pressure) and with a green solution (water as the solvent). Due to the combined synergic effects of the Lewis basicity of TMU-frameworks, the amphoteric and hydrogen bond-participating nature of water molecules, maximum conversion times are reached just after 30 min (for TMU-5) and 60 min (for TMU-34). Stability and recyclability tests show that TMU-5 and TMU-34 are completely stable in water at reaction conditions and can retain their crystallinity, porosity, and functionality even after five cycles without any specific reduction in their catalytic conversion. Since, in many cases, amine decorated MOFs are applied in Knoevenagel catalyzed condensation, this study is beneficial in providing information about the effects of azine and tetrazine functional groups in reactant activation and the acceleration of Knoevenagel condensation.
A covalent modification strategy for di-alkyne tagged metal-organic frameworks to access efficient heterogeneous catalysts toward C-C bond formation
Liang, Qianqian,Cheng, Hua,Li, Chengwen,Ning, Liangmin,Shao, Liming
, p. 1210 - 1221 (2022/02/07)
Organic and inorganic building blocks are used to construct a class of metal-organic frameworks (MOFs) that exhibit tremendous chemical tunability. In this study, a novel zirconium-based MOF UiO-66-(alkyne)2 with a di-alkyne tag was obtained through solvothermal pre-synthesis, which provides a potential covalent binding site for post-synthesis modification. On this basis, a gentle post-synthesis modification strategy based on covalency was expanded for introducing diverse metals, and a family of isostructural tailored materials (UiO-66-alkyne-Co, UiO-66-(alkyne-Co)2 and UiO-66-(alkyne-Ni)2) with base metals Ni or Co were designed and synthesized successfully. Among them, di-alkyne tagged UiO-66-(alkyne-Co)2 has shown unprecedented remarkable performance as a heterogeneous catalyst for the Knoevenagel reaction, completely converting benzaldehyde in just 5 min at room temperature, to our knowledge, faster than the reported MOF catalysts. Moreover, UiO-66-(alkyne-Co)2 maintains high stability and functionality after five cycles, and the catalytic activity is also preserved in the gram level scale-up experiment, indicating that UiO-66-(alkyne-Co)2 has great potential for practical application in the formation of C-C bonds. In a sense, this research provides an ideal platform for anchoring the required functional groups on alkyne-modified MOFs, which lays a foundation for finding more potential applications of MOF materials in the future.
