Alkali Metal Ion-exchange in a Metal-Organic Framework Based on Lanthanum and 1,4-Phenylenebis(methylidyne)tetrakis(phosphonic acid)

The ion-exchange selectivity of four metal-organic frameworks (denoted as MLaL), formed by alkali metal ions (M⁺), La³⁺, and 1,4-phenylenebis(methylidyne)tetrakis(phosphonic acid) (L), was examined. Unusual selectivity for the alkali metal ions was observed, which did not follow the previously proposed mechanism that was explained based on the ion-size similarity in the framework. The changes in the crystal structures after ion-exchange reactions were observed by powder X-ray diffraction analysis. The change in the lattice energy in a mixed-metal framework is likely to be one of the significant parameters to affect ion-exchange selectivity.

Bi Metal-Organic Framework (Ce/Ni-BTC) as Heterogeneous Catalyst for the Green Synthesis of Substituted Chromeno[4, 3-b]quinolone under Solvent Free Condition

AIMS

Novel bi metal organic framework (b-MOF) is synthesized and used as a heterogeneous catalyst for the synthesis of chromeno[4, 3-b]quinolone derivatives via one-pot and solvent-free, four-component reaction of dimedone, aromatic aldehydes, 4-hydroxycoumarin and ammonium acetate at 110°C.

BACKGROUND

b-MOFs can be used as a heterogeneous catalyst in the synthesis of many organic compounds. The active and multi-purpose sites in b-MOFs provide a varied function in their catalytic applications. In this paper, reductive CES method is applied for the synthesis of Ce_0.47/Ni_0.53-BTC b-MOF. The resulting b-MOF was used as a heterogeneous catalyst for the synthesis of chromeno[4, 3-b]quinolone via one-pot and solvent-free, fourcomponent reaction of dimedone, aromatic aldehyde, 4-hydroxycoumarin and ammonium acetate at 110 °C.

METHOD

Ce_0.47/Ni_0.53-BTC was synthesized in an electrochemical cell composed of a stainless steel foil with a size of 5cm×5cm centered between two 5cm×5cm sized graphite plates as the anodes by the cathodic current density of 0.2 A/dm² and placed in a solution of cerium nitrate (0.3 g), nickel nitrate (0.3 g), H₃BTC (0.2 g) and NaNO₃ (0.1 g) in ethanol (500 mL). Ce_0.47/Ni_0.53-BTC (10 mg) was added to a mixture of dimedone (1 mmol), aromatic aldehyde (1 mmol), hydroxycoumarin (1 mmol) and ammonium acetate (1.5 mmol) and stirred at 110 °C under solvent-free conditions for 45 min. The reaction evolution was controlled by the TLC (hexane:ethyl acetate, 4:1). Then, boiling ethanol was added to the reaction mixture and stirred at room temperature for 15 min. After the reaction completion, the catalyst was separated by centrifuge. Finally, the reaction mixture was placed in an ice bath, which resulted in a white solid product and recrystallized from ethanol to give the pure product.

RESULT

The b-MOF catalyst showed very good efficiency in the synthesis of the desired compounds and can be easily recovered by centrifuge and reused at least five times without a decrease in catalytic activity.

CONCLUSION

In this report, a novel bi metal-organic framework (Ce0.47/Ni0.53-BTC) is synthesized via the cathodic electrosynthesis method. The synthesized b-MOF is fully characterized by several characterization methods. The catalytic activity of Ce0.47/Ni0.53-BTC is investigated in the synthesis of chromeno[4, 3-b]quinolone derivatives via one-pot four-component reaction of dimedone, aromatic aldehyde, 4-hydroxycoumarin and ammonium acetate. The reaction optimization results showed that the highest isolated yield was obtained when the reaction was performed in solvent-free conditions at 110 °C. The catalyst showed to be highly efficient in the synthesis of the desired compounds and performing the reaction utilizing various starting materials gave the products in good isolated yields, which proves the generality and the scope of the method. The catalyst could easily be recovered by centrifuge and reused at least five times without a decrease in catalytic activity.

Mixed-Metal MOFs: Unique Opportunities in Metal-Organic Framework (MOF) Functionality and Design

Mixed-metal metal-organic frameworks (MM-MOFs) can be considered to be those MOFs having two different metals anywhere in the structure. Herein we summarize the various strategies for the preparation of MM-MOFs and some of their applications in adsorption, gas separation, and catalysis. It is shown that compared to homometallic MOFs, MM-MOFs bring about the opportunity to take advantage of the complexity and the synergism derived from the presence of different metal ions in the structure of MOFs. This is reflected in a superior performance and even stability of MM-MOFs respect to related single-metal MOFs. Emphasis is made on the use of MM-MOFs as catalysts for tandem reactions.