Preparation Of PLNPs@MOFs Composites And Their Photocatalytic Properties

At present,water pollution has become a worldwide environmental problem.Eighty percent of the world’s population is threatened by water security.Rhodamine B and Cr（Ⅵ）,common pollutants in polluted water,are carcinogenic and mutagenic.Among them,Cr（Ⅵ）as one of the common heavy metal pollutants,mainly from leather,electroplating and other industrial wastewater discharge.Residents in areas with serious water pollution are prone to rhinitis,bronchitis,tuberculosis and diarrhea,which will irritate and corrode the respiratory tract once inhaled.Therefore,removing Rhodamine B and Cr（Ⅵ）from water is very important for environmental protection.Adsorption,precipitation,membrane filtration and electrochemical technologies have been used to treat contaminated water,but many of these processes have high operating costs,limited efficiency,and problems such as secondary pollution.Solar based photocatalysis technology is considered one of the most promising methods for contaminated water treatment due to its clean,inexhaustible energy supply,sustainability and absence of secondary pollution.The photocatalyst cannot catalyze the reaction under dark or unstable weather conditions,which severely limits the application of photocatalysis technology under dark conditions.In order to solve the above problems,researchers combined long persistence luminescent nanomaterials（PLNPs）with photocatalysts to prepare round-the-clock photocatalysts.However,in round-the-clock photocatalytic systems assisted by long persistence luminescent nanomaterials,PLNPs still have some problems such as short afterglow time,poor catalytic performance and short photocatalytic reaction maintenance time under dark conditions.Based on the above questions,in this paper,PLNPs(Zn₃Ga₂Ge₂O₁₀:0.5%Mn)with ultra-long afterglow was combined with metal organic Framework（MOFs）to construct an round-the-clock photocatalyst with continuous fluorescence resonance energy transfer（PLRET）for photocatalytic degradation of pollutants.The main research work includes the following parts:（1）Zn₃Ga₂Ge₂O₁₀:Mn long persistence luminescent nanomaterials have been prepared by hydrothermal method and have an ultra-long afterglow of up to 16 days.And explore its optical properties,catalytic properties,the experimental results showed that when the p H value was 7,the calcination temperature was 950℃,and the doping amount of Mn was 0.05%,the catalytic degradation performance of Rh B was the best.（2）MOFs（NH₂-MIL-101（Fe））were prepared by hydrothermal method,and then PLNPs was combined with MOFs by covalent bond.The mass ratio of PLNPs to MOFs composite was studied,and the round-the-clock photocatalytic degradation of Rh B and photocatalytic reduction of Cr（Ⅵ）were investigated.The results show that the PLNPs@MOFs composite photocatalyst with the optimum mass ratio of 1:1 has excellent round-the-clock photocatalytic activity.（3）NH₂-MIL-125（Ti）was prepared by hydrothermal method,and Ag nanoparticles were deposited on the surface of the material by photoreduction deposition,so as to increase the absorption range of NH₂-MIL-125（Ti）to visible light.Then PLNPs and Ag/NH₂-MIL-125（Ti）were combined by covalent bond.Zn₃Ga₂Ge₂O10:0.5%Mn@Ag/NH₂-MIL-125（Ti）composites were prepared and the photocatalytic degradation performance of the composites was investigated.The results showed that the deposition of Ag nanoparticles not only widened the absorption range of visible light of the composites,moreover,the photocatalytic degradation performance of the composites was improved.The PLNPs prepared by us has an ultra-long afterglow of up to16 days,which enables the material to continue to support the photocatalytic reaction after the light source is turned off,and enables the composite to have long-lasting photocatalytic activity.In this work,PLNPs material with ultra-long afterglow and MOFs are cleverly used to form a new round-the-clock photocatalyst with PLRET effect,which realizes the photocatalytic degradation of pollutants under round-the-clock conditions,greatly improves the catalytic efficiency,reduces the cost of environmental governance,and provides a new strategy for the efficient utilization of photocatalysts.The photocatalyst has excellent potential for environmental protection.