The Photocatalytic Degradation Properties Of MOFs-derived Metal Oxides Coated With Organic Semiconductors

Water environmental problems are becoming more and more serious,the misuse of antibiotics will make a huge potential threat to aquatic wildlife and human beings.Traditional technologies such as physics,chemical adsorption and biological treatment are difficult to effectively remove antibiotics,it is urgently to explore more effective ways to eliminate the water pollution problem caused by antibiotics.The metal-organic frameworks（MOFs）exist high surface area,multi-active site and ordered pore structure and the presence of the variable metal ions is more conducive to the activation of persulfates such as peroxymonosulfate（PMS）with the producing of·SO₄^-and·OH and the transformation of more active species,which achieve the effective degradation for the organic pollutants.However,it is difficult to solve the problem for the recombination of e^--h⁺,the typical n-type organic semiconductor perylene bisimide and its derivatives are widely used in the field of photocatalytic field because of its excellent visible light absorption ability and high charge mobility.Therefore,a simple method of oil bath was used to self-assembly perylene diimide（PDIs）on the surface of the metal oxide with different element derived from MOFs,which is beneficial for the transmission of electronic,the separation of e^--h⁺and remove organic pollutants efficiently.The main research contents and conclusions in the paper are as follows:（1）PDIs semiconductor was self-assembled on the surface of C,N and S modified porous Ce O₂ derived from MOF-808（Ce）by a simple oil bath heating method.The original MOFs morphology was maintained and a n-n heterogeneous structure was constructed successfully.UV-vis absorption spectra showed that the successful self-assembly of PDIs expanded the visible light absorption capacity of C,N,S-Ce O₂.The presence of variable metal cerium ion accelerated electron transfer and promoted the photodegradation efficiency of tetracycline（TC）to 80.1%within 30 min under the visible light irradiation.The apparent reaction rate constant（k）is 29.63times than that of the monomer（C,N,S-Ce O₂）.Radical capture experiments and electron spin resonance（ESR）analysis showed that·O₂^-,h⁺,·OH and ¹O₂ were all involved in photocatalytic degradation,and·O₂^-was the most important active species.（2）Three-dimensional porous spherical shell composite of 25%PDIs/Co₃O₄@C was prepared by a simple hydrothermal and oil bath method.Carbon-doped Co₃O₄ was obtained by the calcination of MOF-74（Co）,which not only retained the original frame structure,but also had a wide range of visible light absorption.Then,PDIs were self-assembled on its surface for the photocatalytic degradation of a variety organic pollutants,such as tetracycline（TC）,enrofloxacin（ENR）,ciprofloxacin（CIP）,sulfadiazine（SDZ）,rhodamine B（Rh B）and methyl blue（MB）.3D spherical shell composite of 25%PDIs/Co₃O₄@C has good cycle stability,strong anti-ion interference ability and excellent photocatalytic performance,100%TC could be degraded within30 minutes,the apparent rate constant k of 25%PDIs/Co₃O₄@C is almost 25.27 times than that of Co₃O₄@C.Capture experiments and ESR showed that·O₂^-and ¹O₂ played a leading role in photocatalytic degradation.（3）The composite material of 20%PDIs/Fe₂O₃@C was successfully obtained by the calcination of MIL-88A（Fe）with a simple hydrothermal and oil bath method.Next,self-assembled PDIs on the surface of nanoparticles.The loading of PDIs effectively improves the high aggregation phenomenon,enhances the specific surface area of the monomer and realizes the effective separation of electron hole pairs.Fe³⁺/Fe²⁺cycling accelerates the activation of PMS and produces more active species,such as·OH,h⁺,·SO₄^-,·O₂^-and ¹O₂.20%PDIs/Fe₂O₃@C sample has prominent degradation advantages,so that could degrade TC in 20 minutes,the apparent rate constant k is 16.4 times that of Fe₂O₃@C.