Preparation Of MOFs-based Pickering Emulsions And Their Catalytic Study Of The Deacetalization-Knoevenagel Tandem Reaction

Metal-organic frameworks（MOFs）,porous materials consisting of organic ligands linked to metal ions,are a new class of porous materials that have been rapidly developed in recent years.MOFs have tunable chemical functionality,porosity and pore size and can be used in a variety of applications.However,it was not until 2013that research into Pickering emulsions prepared from MOFs began,as the previously reported MOFs were unstable in the presence of water.With the introduction of water-tolerant MOFs,these porous materials can then be used as emulsifiers to generate Pickering emulsions,which can then be applied to the synthesis of hybrid materials and interfacial catalysis.Benzylidene malononitrile derivatives（BMDs）are a series of compounds derived from the substitution of the H atom at the alpha position of the cyano group of a malononitrile derivative with other groups.Because of their inherent outstanding chemical and biological activity,BMDs have found a wide range of applications in the fields of pharmaceuticals,dyes and pesticides,and scientists have been working on the preparation and synthesis of BMDs,which will help to provide an important basis for the production of pharmaceuticals,pesticides and dyes.Currently such reactions are usually catalysed by homogeneous catalysts in a single system,the main drawback of which is that the catalysts cannot be used repeatedly and are not very effective,which leads to high costs in the production process.The development of environmentally friendly non-homogeneous catalysts or highly efficient reaction systems is therefore of crucial importance for the application of such reactions in practical production.Whereas multi-step reactions tend to be long and energy intensive,tandem reactions can be realised with maximum energy savings,resulting in a sustainable process.Therefore,this paper focuses on the synthesis of water-stable MOFs with good structural stability and properties through the synthesis of various metal ions and various ligands for the preparation of Pickering emulsions,which were analysed with the aid of XRD,TEM,FT-IR and TGA instrumentation,and MOFs-based Pickering emulsions to catalyse the Deacetalisation-Knoevenagel tandem reaction with MOFs-based Pickering emulsions,the catalytic effect was excellent and it was shown that the catalysts could be recycled and reused several times.The work is divided into four parts:Chapter 1 introduces the preparation of metal-organic frameworks materials and their applications and the study of MOFs-based Pickering emulsions,reviews the recent trends in tandem reactions,and explains the significance of our chosen research for this paper.Chapter 2 presents the detailed steps for the synthesis of a series of MOFs materials with various ligands and various metal ions,the preparation of MIL-101-NH₂,Ui O-66-NH₂ and ZIF-8,and the preparation of Pickering emulsions using them as emulsifiers.Chapter 3 focuses on the preparation of MOFs-based Pickering emulsions with optimum water-oil ratios from various MOFs materials and their catalytic Deacetalization-Knoevenagel tandem reaction at 80℃with reactive methylene compounds such as benzaldehyde dimethyl acetal and malononitrile with different functional groups.Among them,ZIF-8-based Pickering emulsions were more effective in catalysis.Chapter 4 is the concluding section,which gives an exhaustive summary of the preparation of Pickering emulsions from MOFs materials and the catalytic reactions.