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

Abstract

The hybrid frameworks M 2 dobdc (dobdc 4-= 2,5-dioxidoterephthalate, M 2+ = Mg 2+ , Co 2+ , Ni 2+ , Cu 2+ and Zn 2+ ), commonly known as CPO-27 or MOF-74, are shown to be active catalysts in base-catalyzed reactions such as Knoevenagel condensations or Michael additions. Rather than utilizing Nfunctionalized linkers as a source of basicity, the intrinsic basicity of these materials arises from the presence of the phenolate oxygen atoms coordinated to the metal ions. The overall activity is due a complex interplay of the basic properties of these structural phenolates and the reactant binding characteristics of the coordinatively unsaturated sites. The nature of the active site and the order of activity among the different M 2 dobdc materials were rationalized via computational efforts; the most active material, both in theory and experiment, is the Ni-containing variant. The basicity of Ni 2 dobdc was experimentally proven by chemisorption of pyrrole and observation by IR spectroscopy.

Solvent-Dependent Structural Variation of Zinc(II) Coordination Polymers and Their Catalytic Activity in the Knoevenagel Condensation Reaction

“…[63][64][65][66][67][68][69][70][71][72][73][74][75][76] This condensation is generally catalyzed by bases or Lewis acids and widely studied in homogeneous systems. 90,91 Only a few studies have employed heterogeneous catalysts including metal organic frameworks.…”

“…49 Recently, we have reported various coordination polymers which are catalytically active for the oxidation of alkanes, alcohols or olefins. [50][51][52][53][54][55][56][57][58][59][60][61] Acidic and basic polymers can exhibit high catalytic activity in condensation reactions like the Pechmann, 62 Knoevenagel, [63][64][65][66][67][68][69][70][71][72][73][74][75][76] and Prins reactions. 77 Coordination polymers can work as catalysts through two different components, viz.…”

Zirconium Materials from Mixed Dicarboxylate Linkers: Enhancing the Stability for Catalytic Applications

“…Recently, other Ni II , Zn, and Cu-based MOFs have been applied to base-catalyzed reactions. [27] From a preparative point of view, one has to take into account that there are not very significant differences between the final yields of the dye obtained on different Zr-MOFs (Table 1, Figure 9), and the UiO-67-NH 2 (20) catalyst is the most active and selective. For the preparative task, we have scaled up the reaction to three times the amounts of reagents and catalyst, and the final product was isolated with a yield of 85 % after 6 h.…”

Using benzene carboxylic acids to prepare zirconium-based catalysts for the conversion of biomass-derived furfural

“…In Zr-based catalysts, Zr 4? and O 2-(carboxylate groups in BCAs) formed the acid and basic sites, respectively (Tang et al 2013;Valvekens et al 2014). Firstly, isopropanol was adsorbed onto the catalyst and interacted with the acid-base sites (Zr 4?…”