Preparation Of Porous Matrix Material With Metal Nano-particles By Emulsion Template Method And Study Of Its Properties

Metal nanoparticles(NPs)are widely used as active components of catalysts because they have excellent catalytic activity and selectivity.Thereby metal nanoparticles have wide applications in various fields of heterogeneous catalysis.However,the naked metal NPs have a strong tendency to aggregate owing to their small size,high surface energy and strong van der Waals interactions,which will cause their instability and the rapid reduction of catalytic activity.At the same time,these NPs are usually difficult to separate,recycle and recover,which increases the cost of their use and also cause secondary pollution of NPs.The all above-mentioned problems limit the wide applications of NPs.Accordingly,the most commonly used solution is to load metal NPs on the different substrates for preparation of supported catalysts,which can remarkably improve the activity,stability,and durability of the catalysts.In general,various porous materials are often used as substrates of metal NPs,so the performance of porous materials has an important influence on its application as support.There mainly include the following three aspects:(1)The binding sites provided by porous materials,which depend on their specific surface area and the internal structures,so the high specific surface area and the appropriate size of pores are desired for obtaining a well-loaded catalyst;(2)The surface chemical properties of the internal pores,which determine the properties of the interaction between the catalytic system(reaction solution system)and the catalyst,and also determine the binding strength of metal NPs and substrates.Their strong interactions will prevent the leak and aggregation of the NPs,resulting in the high catalytic activity during the catalysis process;(3)The mass transfer of porous materials is very important for properties of supported catalysts.The faster mass transfer can be offered via minimizing the channel blocking from tiny cavity.It is generally accepted that the commonly used method is to prepare the hierarchical porous materials combined micro-,meso-,and macropores.Obviously,the properties of the above-mentioned porous substrates are determined by their physical and chemical properties and their preparation methods.Up to date,the main methods of preparation of porous substrates include sol-gel method,emulsion-template method(soft template),hard template method,and direct synthesis method.Among them,emulsion-template method is the most ideal way to prepare hierarchical porous materials because of its simplicity,low cost,friendly environment and easy to manufacture on a large scale.As for emulsion-template method,however,the heterogeneousity and the poor controllability of structural pores are the bottlenecks for its application.The essential issue is the instability of interfaces in the system,so the establishment and understanding of the stable interface are the key to solve this problem.Based on the above-mentioned research background and the previous efforts in our group,the supported catalysts loading non-noble metal NPs(Cu,Co,and Ni)were prepared by using the emulsion-templated amino-functional porous organosilica monoliths as supported materials,and their catalytic properties were correspondingly studied in this thesis.At the same time,the super-stable and rigid interfacial film can constructed by self-assembling of a special stabilizer with strong aggregation property at the O/W interface.As a result,as-prepared interface film can be used to resist coalescence,demulsification,and phase inversion in emulsion systems,which were caused by the changes of micro-environment.To do this is aimed at achieving the controllable and effective preparation of the hierarchical porous substrate materials.Specifically,the major work was done by the following two aspects:In the first part of the thesis,the composite Cu NPs/amino-functionalized porous organosilica monoliths(Cu/OSMs)with excellent catalytic degradation performance of colored dyes were created by the emulsion-template method.It is demonstrated that the loading process of Cu NPs does not cause destruction of the porous structure of OSMs.Moreover,it can be clearly observed that a large number of copper nanoparticles are loaded on the skeleton of the OSMs from the results of FE-SEM images.Further,the distribution and the valence state of Cu NPs were confirmed through EDS,XPS and XRD measurements.On this basis,the catalytic performance of Cu/OSMs in degradation of 4-NP,MB,RhB,MO and mixed dyes were investigated,indicating the highly efficient catalytic degradation.More interestingly,the efficiency of 0.5-Cu/OSM-P on catalytic degradation of 4-NP still remained as high as 95%after fourteen recycles.In addition,it is found that the composite porous organosilica monoliths catalysts combining Co(Co/OSMs)and Ni(Ni/OSMs)can be prepared by using the above-mentioned method,suggesting the general method for preparation the supported catalyst loading metal NPs.At the same time,Co/OSMs and Ni/OSMs show the excellent catalytic performance of 4-NP catalytic degradation.We strong believe that the strategy developed in this work is very useful for simple,low-cost and environmentally friendly preparation of supported catalysts containing non-noble metal.In the second part of the thesis,inspired by the specific structure of Chol-OH in the first part of the work and its successful application in the preparation of porous organosilica monolithic materials.We designed and synthesized amphiphilic perylene compound(compound 6)as stabilizer molecules for obtaining excellent stable interfaces in emulsion systems.On this basis,COFs materials can be prepared by the emulsion-templated method.The amphiphilic properties were studied by using the compound 6 as a stabilizer,the mixture of acetic acid,ethanol and deionized water as aqueous phase,the mixed solution of TAPT,mesitylene and 1,4-phthalaldehyde as the oil phase.The result shows that the stability of the emulsion is excellent,and the size of the emulsion droplets is uniform.We prepared porous covalent organic frameworks materials using as-prepared emulsion as template.It is found that the as-synthesized COFs material possess the hierarchical porous structures combined micro-,meso-,and macropores.Further COFs materials exhibit the ordered micropores and certain crystallization from the results of SEM,TEM and XRD measurements.Therefore,the amphiphilic perylene compound in this work has great potential in preparing COFs materials with severe reaction conditions,which lays a foundation to synthesize highly crystallized COFs by using emulsion-template method.