Preparation Of Carbonized Derivatives Of MIL-125 And Its Application In Ultrasonic Catalytic Degradation Of Organic Dye

Rhodamine B（RhB）and other organic dyes have bright color,stable coloring,low price and other special properties,so they are widely used in many industrial fields.However,the stability of the structure and properties of organic dyes bring some difficulties in water pollution control.Ultrasonic catalysis provides a green and sustainable strategy for the degradation of organic pollutants,and the assistance of MOF materials is conducive to enhancing the degradation performance of ultrasonic catalysis,which is mainly reflected in the following aspects:（1）The preparation process of MOF material is refined and the purity of synthesis is high;（2）The porous structure of MOF materials results in a large specific surface area,which is beneficial to the contact and adsorption of organic molecules over a large range;（3）MOF materials have lots of active catalytic sites,providing thousands of REDOX reaction space in ultrasonic catalytic degradation process.However,most MOFs also show some physical and chemical weaknesses that cannot be ignored in ultrasonic catalysis.The most important point is that they have a large electron transition band gap,which restricts the separation of electron-hole pairs.Furthermore,the progress of REDOX reaction is affected,which hinders the application of MOFs in the field of catalytic degradation to a certain extent.For this reason,,MIL-125（Ti）was used as the precursor in this paper.By means of carbonization and atomic doping,we prepared a series of composite materials containing TiO₂,porous carbon and other components.At the same time,organic molecules such as Rh B were used as dye models to build an ultrasonic catalytic degradation system with excellent performance.The main research contents are as follows:1.Preparation of porous carbon based TiO₂composites（PC@TiO₂）and the study on ultrasonic catalytic degradation performance.In this study,MIL-125（Ti）was synthesized by solvothermal method.Then,MIL-125 was used as a precursor to successfully prepare a novel porous carbon based TiO₂composite（PC@TiO₂）by high temperature carbonization.At the same time,the catalytic properties and mechanism of Rh B degradation were studied.The research shows that a small number of carbon atoms will be doped into the crystal structure of TiO₂,so that the band gap width of the composite material is effectively reduced,and the wavelength range of light absorption is significantly expanded.Moreover,porous carbon components have graphite-like structure,which can transport electrons and reduce the recombination probability of excited electrons and holes.Due to the retention of a large number of organic skeletons,PC@TiO₂still has a large specific surface area and more pore structure,which provides abundant active catalytic sites for REDOX reactions.Through a series of degradation experiments,PC@TiO₂showed excellent ultrasonic catalytic activity,and the removal rate of organic dye Rh B reached almost 100%within 60 minutes.In addition,by kinetic and thermodynamic analysis,the adsorption/ultrasonic catalysis mechanism of PC@TiO₂in the degradation process is proposed and explained.2.Preparation of bimetallic core carbon matrix composites（Cu-PC@TiO₂）and the study on ultrasonic catalytic degradation performance.Cu atoms are doped into MIL-125（Ti）to form bimetallic center MOFs by solvothermal assisted atomic doping,which named Cu-MIL-125（Ti）.Cu-MIL-125（Ti）is converted into a novel carbon-based material with a bimetallic center Cu-PC@TiO₂by high temperature carbonization.It is found that the newly synthesized material reduces its band gap and expands its response range to light by replacing the original metal nodes with Cu atoms.Some Cu groups exposed on the surface of Cu-PC@TiO₂,which can cooperate with graphite-like structures to accelerate the transfer of surface electrons,at the same time,inhibit the recombination of excited electrons and holes.The experimental results showed that,compared with PC@TiO₂,the ultrasonic catalytic degradation time of Cu-PC@TiO₂was reduced by 80%,and the Rh B removal effect of Cu-PC@TiO₂could reach nearly 100%within 10 minutes under ultrasonic radiation.Cu-PC@TiO₂can also rapidly degrade Methylene Blue（MB）by ultrasonic catalysis,which indicates that Cu-PC@TiO₂has the universal ability to degrade organic dyes.