Fabrication of amino-functionalized Fe3O4@Cu3(BTC)2 for heterogeneous Knoevenagel condensation

Interface-Active Metal Organic Frameworks for Knoevenagel Condensations in Water

It is desirable but challenging to locate solid catalysts at the oil-water interface to stabilize “Pickering emulsions”, which is one of the promising ways to develop efficient green chemical processes. Herein, water-stable metal organic framework ZIF-8 without any chemical modification was demonstrated to be an interface-active catalyst for Knoevenagel condensation in a biphasic system. Pickering emulsion formed under the reaction conditions due to its amphiphilic property, which was beneficial to the mass transfer and led to high catalytic performance. Moreover, it can be repeatedly applied for Knoevenagel condensation for at least six successive cycles without losing its catalytic activity and framework integrity.

Amine-Functionalized Sugarcane Bagasse: A Renewable Catalyst for Efficient Continuous Flow Knoevenagel Condensation Reaction at Room Temperature

A biomass-based catalyst with amine groups (–NH₂), viz., amine-functionalized sugarcane bagasse (SCB-NH₂), was prepared through the amination of sugarcane bagasse (SCB) in a two-step process. The physicochemical properties of the catalyst were characterized through FT-IR, elemental analysis, XRD, TG, and SEM-EDX techniques, which confirmed the –NH₂ group was grafted onto SCB successfully. The catalytic performance of SCB-NH₂ in Knoevenagel condensation reaction was tested in the batch and continuous flow reactions. Significantly, it was found that the catalytic performance of SCB-NH₂ is better in flow system than that in batch system. Moreover, the SCB-NH₂ presented an excellent catalytic activity and stability at the high flow rate. When the flow rate is at the 1.5 mL/min, no obvious deactivation was observed and the product yield and selectivity are more than 97% and 99% after 80 h of continuous reaction time, respectively. After the recovery of solvent from the resulting solution, a white solid was obtained as a target product. As a result, the SCB-NH₂ is a promising catalyst for the synthesis of fine chemicals by Knoevenagel condensation reaction in large scale, and the modification of the renewable SCB with –NH₂ group is a potential avenue for the preparation of amine-functionalized catalytic materials in industry.