Metal-organic Frameworks Were Used As Self-template To Construct Catalysts For Pollutant Removal

With the rapid development of social economy and industrial production,the problem of water pollution is becoming more and more serious.Solar-driven semiconductor photocatalytic degradation and advanced oxidation processes are important ways to remove pollutants.In this paper,a series of MOFs-derived composite catalysts were prepared by calcination and sulfidation using metal organic frameworks(MOFs)as self-templates.The structure,composition and photoelectrochemical properties of the composite catalysts were characterized.The photocatalytic reduction of Cr(VI),hydrogen production from water decomposition and activation of H2O2 to remove tetracycline(TC)were investigated.The research content mainly has the following parts :(1)Carbon quantum dots@In2S3(CQDs@In2S3)hollow tubes with a lamellar structure were prepared by sulfurization using In-MIL-68 as a template for photocatalytic reduction of Cr(VI).Compared with In2S3,CQDs@In2S3 has higher electron-hole separation efficiency.In the solution with p H of 5.5,CQDs@In2S3-2showed the best Cr(VI)reduction rate,which was close to 100% at 60 min,and the apparent rate constant(k)was 0.062 min–1,which was 4.3 times higher than that of In2S3.At the same time,the catalyst has good recycling performance.Free radical capture experiments showed that ·O2– was the main active species for Cr(VI)reduction.(2)Co-encapsulated N-doped carbon(Co@NC)was prepared by calcination using ZIF-8@ZIF-67 as template,which was used to modify cadmium selenide quantum dots(Cd Se QDs)to prepare Co@NC/Cd Se composite catalysts.The photocatalytic reduction of Cr(VI)and hydrogen production performance of the catalyst were investigated.The modification of Co@NC significantly improves the visible light absorption and photogenerated charge separation performance of Cd Se.The Cr(VI)reduction apparent rate constant of the optimal prepared 2%Co@NC/Cd Se was 0.095 min–1,which was33.9 times that of Cd Se.Free radical capture experiments confirmed that e– and H2O2 were the main active species for Cr(VI)reduction.In addition,the H2 evolution rate of2%Co@NC/Cd Se in 10% lactic acid solution was 6.48 mmol g–1 h–1,which was about58.9 times that of Cd Se.(3)Fe/Co3S4 bimetallic composite catalyst was prepared by sulfurization of Fe3+doped ZIF-67 template,which was used to activate H2O2 to remove TC.The hollow structure of the catalyst,the electron transfer between Co-S-Fe and the redox cycle between Co3+/Co2+ and Fe3+/Fe2+ improved the ability of the catalyst to activate H2O2.The TC removal rate of the optimal 10%Fe/Co3S4 sample was 97 % within 45 min,and the apparent rate constant was 0.19 min–1,which was 1.9 times that of Co3S4.At the same time,the catalyst has good cycle stability and anti-interference.Free radical capture experiments confirmed that ·OH,·O2– and 1O2 were the main free radicals in this reaction,and two ways of TC degradation were proposed.