Design and Assembly of a Hierarchically Micro- and Mesoporous MOF as a Highly Efficient Heterogeneous Catalyst for Knoevenagel Condensation Reaction

Abstract

A 3D hierarchically micro- and mesoporous MOF, [Tb6(μ3-OH)8·(2-FBA)2·(H2O)6·(DCBA)2]·10DMF·4H2O (namely, Tb-DCBA), was successfully constructed by the coordination self-assembly process between H4DCBA linker and Tb6 hexanuclear cluster. By virtue of preferable physicochemical stability, high surface area, multiple porosity, and abundant amino functional groups, Tb-DCBA is not merely considered as a greatly potential heterogeneous catalyst for Knoevenagel condensation reaction, but also has remarkable repeatability for reusing at least four times. It is worth noting that micro- and mesoporous MOF is still an urgent and enormous challenge, because such MOFs are difficult to synthesize and determine precise structures, and always possess relatively poor stability to limit their practical applications. Hence, this work creates a scarce opportunity for a hierarchically micro- and mesoporous MOF for investigating its catalytic performance.

Nanochannel-based {BaZn}–organic framework for catalytic activity on the cycloaddition reaction of epoxides with CO2 and deacetalization-Knoevenagel condensation

“…In terms of documented references, because of the plentiful Lewis acidic and basic sites including Zn(II), Ba(II), carbonyl oxygen atoms and N pyridine atoms, NUC-51a is a potential bifunctional heterogeneous catalyst for deacetalization-Knoevenagel condensation. 60,61 Especially, the coordination of unsaturated Zn(II) and Ba(II) as Lewis acidic sites can promote initial deprotection of an acetyl part, and then the N pyridine atoms and uncoordinated carbonyl oxygen atoms as Lewis basic sites may be conducive to the deprotonation of an active methylene group, which can greatly facilitate the smooth progress of the deacetalization-Knoevenagel condensation reaction. 62,63 Therefore, benzaldehyde dimethyl acetal and malononitrile were chosen as model reactants in DMSO solvent to investigate the optimal catalytic conditions, such as reaction temperature, time and catalyst dosage.…”

“…36,37 In addition, hitherto, recent studies have confirmed that activated microporous MOFs materials had other catalytic properties for organic reactions, such as Knoevenagel condensation reaction, Friedel-Crafts reaction, cyanosilanation, acetalization of carbonyl compounds and imines, aldehyde alcohol reaction, etc. [38][39][40][41] The deacetalization-Knoevenagel condensation is specifically important to produce unsaturated methylene compounds, which could be used as the raw materials of pharmaceuticals, coumarin derivatives, cosmetics, perfumes and so on. 42,43 Therefore, it is meaningful to explore the synthesis of microporous MOFs with the advantages of diverse catalytic sites, high specific surface area, special pore (cavity) structure, and high selective catalysis.…”

Knoevenagel Condensations Catalyzed by New Oil Shale Recyclable Catalyst at Room Temperature and Assisted by Ultrasounds Irradiations

“…Too many catalysts have been reported since the first synthesis of Knoevenagel condensation which was catalyzed by diethylamine 13 and showed then that this transformation needs a basic catalyst. In this regard, researchers developed many basic catalysts which could generate this transformation such as metal oxides such mesoporous Mg-Fe bi-metal oxides and Fly ash supported calcium oxide 14,15 , Metal-organic framework [16][17][18] , phosphates catalysts 19,20 , Dolomite 21 , alkali metal hydroxide such LiOH 21 and a limited variety of acid catalysts were also reported, we mentioned in this regard polymer-metal complex PS-TiCl 4 23 and Nano-crystalline HoCrO 4…”

Ship‐in‐bottle preparation of multi‐SO3H functionalized ionic liquid@MIL‐100(Fe) for acid‐catalyzed ring‐opening of epoxides

“…The unique properties of these materials including high surface area, ultrahigh porosity, adjustable pore dimensions, and surface functionalization possibilities make them as promising candidates for potential applications in the field of heterogeneous catalysis. [1][2][3][4] Although various MOFs are directly used as solid catalysts in different organic reactions, most of them require functional active sites within their framework to promote the chemical transformations. Hence, several researches have been done to insert a broad range of functional species within the nanocages of MOFs through the post-synthetic modification (PSM).…”