Highly Robust Metal–Organic Framework for Efficiently Catalyzing Knoevenagel Condensation and the Strecker Reaction under Solvent-Free Conditions

Abstract

Metal−organic frameworks (MOFs) have been recognized as one of the most promising porous materials and offer great opportunities for the rational design of new catalytic solids having great structural diversity and functional tunability. Despite numerous inherent merits, their chemical environment instability limits their practical usage and demands further exploration. Herein, by employing the mixed-ligand approach, we have designed and developed a robustfor the Indian Institute of Technology Kharagpur), which exhibited excellent framework robustness not only in water but also in a wide range of aqueous pH solutions (pH = 2−12). Taking advantage of superior framework robustness and the presence of high-density open metal sites, IITKGP-50 was further explored in catalyzing the two-component Knoevenagel condensation reaction and three-component Strecker reactions. Moreover, to verify the size selectivity of IITKGP-50, smaller to bulkier substrates in comparison with the MOF's pore cavity (8.1 × 5.6 Å 2 ) were employed, in which relatively lesser conversions for the sterically bulkier aldehyde derivatives confirmed that the catalytic cycle occurs inside the pore cavity. The easy scalability, lower catalyst loading compared to that of benchmark MOFs, magnificent conversion rate over a wide range of substrates, and excellent recyclability without significant performance loss made IITKGP-50 a promising heterogeneous catalyst candidate.

Nanoporous {Pb3}-Organic Framework for Catalytic Cycloaddition of CO2 with Epoxides and Knoevenagel Condensation

“…As shown in entries 1 and 2, reactants with alkyl substituents could undergo very thorough transformations with a yield of 99% within 4 h. For substrates with an aromatic benzene ring (entries 3−9), the significantly reduced catalytic efficiency could be attributed to the steric hindrance effect, which limits the effective movement of molecules in the pores and the efficiency of contact with active sites. 67,68 In addition, it could be found from entries 4−8 that electron withdrawing groups were more advantageous for catalytic efficiency than electron donating groups, basically following the order of electron absorption ability, F > Br > NO 2 > CH 3 > OH.…”

Catalytic comparison of cyanosilylation/Knoevenagel condensation reactions by Pb-based heterometallic organic frameworks with different second metal ions

“…26–29 The reaction is also well known for its application in the synthesis of aldehydes, ketones and reactive methylene compounds to α,β-unsaturated carbonyl compounds. 30–32 Nowadays, many catalysts based on Lewis acid–base sites, main group elements and transition metals have been reported for cyanosilylation and Knoevenagel condensation reactions.…”

Metal–organic frameworks constructed using acid–base mixed ligands, carboxylic acids and N-containing chalcone, and their catalytic performance for Knoevenagel condensation

“…26 The mixed-ligand synthetic strategy, especially in the acid–base system, could compensate for charge balance, coordination deficiency, repulsive vacuum, and weak interaction simultaneously. 27–29 For example, Ge et al synthesized a novel Dy-MOF by a mixed-ligand strategy under solvothermal conditions and the crystalline material exhibits unprecedented versatility, including reversible luminescence response to pH, magnetism, and proton conduction. 30 Zang et al have constructed two amino functionalized Zn/Cd-MOFs through the mixed-ligand strategy, and the two MOFs show good performances in gas adsorption and catalysis of Knoevenagel condensation reactions.…”