Application Of The Photocatalyst Based On Acid Modulated Fe-Based MOFs For The Organic Pollutants

With the rapid development of economy and society,environmental pollution has been paid more and more attention.In particular,persistent refractory organic pollutants because of the long existence in the ecosystem and the effect of teratogenic carcinogenic mutagenesis,has been paid more and more attention.Antibiotics,one of the most typical organic pollutants,mainly come from the extensive use of antibiotics in medicine,animal husbandry,aquaculture and other industries,which have potential harm to the ecological environment and human genes.Thus,the unprecedented attention has been paid to the effective control of antibiotic wasterwater.Recently,the emerging photocatalysis technology has attracted great interest of reseachers because of its environmental friendliness,green environmental protection,simple preparation and high treatment efficiency.Metal organic framework materials（MOFs）are a kind of porous crystal materials with periodic network structure constructed by metal or metal clusters and organic ligands.MOFs with orderly structure and adjustable pore size,modified metal clusters and organic ligands were applied in the application of gas storage,electrochemical detection,fluorescent detection,and drug delivery.Especially with the semiconductor properties,it has a wide application prospect in the field of photocatalysis.MIL-53,as a number of Fe-based MOFs,the Fe-μ₃-O cluster in which can be excited by visible light and has excellent photocatalytic activity.However,it is easy to combine photogenerated electron and holes,so new strategies are needed to improve the photocatalytic activity of Fe-based MOFs.To solve the above problems,three new types of MIL-53series photocatalysts were prepared by using the strategies of defective MOFs by acid modulator and defective heterojunction MOFs as well as the nanoparticles were encapsulated in the MOFs.In this paper,common anti-biotetracycline pollutants were selected as the treatment objects to evaluate the photocatalytic ac tivity of different new photocatalysts.A series of methods were applied to characterize the morphology and size,crystal structure,and explore the optical and electrical properties and the band gap and energy level structure has been carried on the exploration.This study revealed the reason of its excellent photocatalytic activity and explored the photocatalytic degradation pathway of pollutants.This study was to provide basic work to build high efficient photocatalyst based on the defective MOFs.The main research results are as follows:（1）It is interesting and meaningful to application of HCl-modulated MIL-53 for the photocatalytic degradation of organic pollutants,providing another possibility for the removal of organic pollutants.The effect of a cid modulator on structure and the photocatalytic activity were emphasically investigated.Structurally,the increased specific surface and new mecroporous structures caused by acid modulator may be related with the defects due to the absence of metal clus ters.The differences in properties,in particular,the photocatalytic properties affected by the differences in structure.Compare with MIL-53,the photocatalytic activity of acid-regulated MIL-53 increased by 1.5 times due to the easier separation of pho togenerated carriers,in addition,the quantitative relationship between the content of modulator and the photocatalytic activity was revealed.Good recycling until the fourth cycles is an important guarantee for reuse.In addition,form the ERP analysis,·O₂^-and·OH are provided by modulated MOFs as driving forces to demineralize the organic pollutants.（2）The adsorption sites for nanomaterials of metal organic frameworks（MOFs）are limited on account of microporous structure,however,the hierarchical mesoporous MIL-53 by acid modulator make it possible for nanomaterials embedding.The hierarchical mesoporous ML-53 was confirmed from the specific surface area（BET）and pore volume distribution combined with scanning electron microscope（SEM）,further heterojunction photocatalyst based on mesoporous MIL-53 was confirmed from the X-ray diffraction（XRD）,infrared spectrum（IR spectrum）,and X-ray photoelectron spectroscopy（XPS）.Compared with the MIL-53with 50.88%,the photocatalytic degradation efficiency of AgI/MIL-53 increased to85.11%,further increased to 96.21%by AgI/D-MIL-53 based on the acid-modulated MIL-53.Meanwhile,the effective separation of photogenenrated electrons and holes was proved from the point of view of photochemistry in AgI/MIL-53.The stability up to four cycles is the guarantee of practical application.Finally,·O2-,·OH and h+are driving forces to demineralize the organic pollutants based on the photocatalytic degradation mechanism of heterostructure.This work provides a basis for the development of heterostructure photocatalyst based on the acid-modulated hierarchical mesoporous MOFs.（3）In this study,acid modulated MIL-53 was assembled in situ on the basis of two-dimensional nano-thin sheet MoS₂.The presence of MoS₂ and HCl has a significant influence on the crystal structure,morphology,specific surface area,and pore size distribution of MOFs.The composite MoS ₂/D-MIL-53 has excellent adsorption properties and photocatalytic properties,especially for high concentration antibiotic wastewater.The morphology of MIL-53 changed from the smooth regular hexahedron to the bitter gourd shape,which greatly increased the specific surface area and could be related to the enhanced adsorption capacity.In terms of adsorption,the adsorption capacity of MoS ₂/D-MIL-53 was 38.716 mg/g and that of 3%MoS₂/D-MIL-53 was 59.836 mg/g,because MoS₂ and HCl played an important role in the changed crystal structure.In terms of photocatalysis,when the initial concentration of TC was 60 mg/L,the photocatalytic degradation efficiency of MIL-53 was 45.3%,and the photocatalytic removal efficiency of 2%MoS ₂/D-MIL-53,3%MoS₂/D-MIL-53,4%MoS₂/D-MIL-53,5%MoS₂/D-MIL-53 was 92.10%,96.04%,86.26%,and 88.73%,respectively.The synergistic effect of MoS ₂ and HCl is the main reason for increasing photocatalytic activity.On the other hand,different contents of MoS₂ have little effect on photocatalytic activity,indicating that the regulating effect of hydrochloric acid is obvious.The optical and electrical analysis shows that HCl plays an important role in promoting electron and hole separation.At the same time,the modified material has good stability and wide applicability,and has a good removal effect on sulfadimethylpyrimidine.This study provides the basic work for the construction of acid-modulated MOF composites based on two-dimensional nanomaterials.