Metal–organic frameworks for catalysis: the Knoevenagel reaction using zeolite imidazolate framework ZIF-9 as an efficient heterogeneous catalyst

Metal-dioxidoterephthalate MOFs of the MOF-74 type: Microporous basic catalysts with well-defined active sites

“…[8] The second group of materials comprises structures lacking the porosity requirements for intraporous catalysis, featuring basic sites mainly at lattice terminating surface sites. Examples of such materials are the Zn-imidazolates ZIF-8 and ZIF-9, [9][10][11] in which the pore windows are too narrow to allow diffusion of most reactants and/or products, or a Ba-3,5-pyrazoledicarboxylate MOF having a limited microporous volume (S BET = 56 m²/g). [12] If catalysis is confined to the outer surface, the catalytic material is used only for a very limited fraction, and the precise nature of the sites at the surface is not always well defined.…”

Synthesis of magnetically recyclable ZIF-8@SiO2@Fe3O4 catalysts and their catalytic performance for Knoevenagel reaction

“…Besides, Nguyen et al also found the increasing of molar ratio between benzaldehyde and MN could lead the increasing of Knoevenagel conversion over ZIF-9 catalyst [32]. The different was that the conversion of the above two reactions was a little bit lower than this work after 4 h. This may be due to the active site of ZIF-8 and ZIF-9 catalysts were not contact fully with the reagents in the Knoevenagel reaction.…”

2.14 Other Condensation Reactions (Knoevenagel, Perkin, Darzens)

“…One-flask tandem Knoevenagel-Michael addition reaction of sulfonimines (41) with diethyl malonate in the presence of catalytic amount of base afforded the corresponding arylidene dimalonates (42) in good yield (Scheme 13). 55 Arylidene dimalonate has the potential to serve as a bone-affinity agent in the treatment of bone disease and as the precursor for the synthesis of 3-Ar-glutaric acid.…”

“…40 Crystalline zeolite imidazolate framework acted as reusable heterogenous catalyst for the Knoevenagel reaction of benzaldehyde with malononitrile. 41 2.14.2.2.1 Microwave-assisted Knoevenagel condensation Triphenylphosphane (Ph 3 P) catalyzed the Knoevenagel condensation of aldehydes with acidic methylene compounds such as ethyl cyanoacetate and malononitrile to afford substituted olefins under solvent-less conditions. 42 In this method, heterocyclic a-cyanoacrylates and a-cyanoacrylonitriles were obtained in high yields.…”