Study On Catalytic Degradation Of Organic Pollutants By Nanocomposites Derived From Copper-based MOFs(Cu-BTC)

The recalcitrant nature of phenols and dyes present in wastewater generated from coking,printing,and dyeing industries impedes their biodegradation,leading to their persistent accumulation in the environment,thereby posing a potential threat to both ecological safety and public health.Currently,heterogeneous Advanced Oxidation Processes（AOPs）represent one of the primary technologies for advanced treatment of organic wastewater.However,these processes are plagued by issues such as low catalyst activity,poor circulation stability,and a limited pH adaptation range.Based on the high specific surface area,easy structural modulation and functional modification of the copper-based metal-organic framework Cu-BTC,we proposed a strategy to construct Cu-BTC derived carbon-multivalent transition metal heterostructures to enrich the reactive sites and improve the cyclic stability.The composites of Cu-BTC and TiO₂,Cu-BTC-derived carbon/Cu-Cu_xO composites（Cu-Cu_xO@C）,and core-shell structure graphitized carbon/Cu-Co bimetallic composites（Cu/Co@C）were synthesized and evaluated for their catalytic performance in the advanced oxidation of organic pollutants.The investigation focused on elucidating the synergistic effect of active multiple sites-heterostructure and the mechanism of radical activation in the photocatalysis/persulfate system.The main findings of this research are presented herein.The main research contents are as follows:（1）A TiO₂@Cu-BTC photocatalytic adsorbent possessing a heterogeneous structure was synthesized and its adsorption-photocatalytic degradation effect on TiO₂@Cu-BTC methylene blue was examined.The findings revealed that the heterojunction interface between Cu-BTC and an optimal quantity of TiO₂ facilitated the efficient separation and transfer of photogenerated electron-hole pairs,thereby impeding the recombination of electron-hole pairs and generating reactive oxygen species.Additionally,the material exhibited commendable adsorption capacity and effectively eliminated methylene blue through a synergistic combination of adsorption and photocatalysis.The TiO₂@Cu-BTC composite achieved a maximum removal efficiency of 88.5%for methylene blue,which was 4.4 and 19.3 times higher than that of Cu-BTC and TiO₂.The pH range of 7.0-11.0 was favorable for the removal of methylene blue,while the performance of the catalytic removal of methylene blue decreased by only 12%after three cycles.（2）The nanocomposite（Cu-Cu_xO@C）consisting of well-dispersed multivalent Cu(Cu⁰,Cu⁺and Cu²⁺,Cu-Cu_xO)embedded in a carbon matrix.The pyrolysis temperature was regulated using Cu-BTC as a self-sacrificing template to overcome the issue of reduced reactivity caused by the agglomeration of nano-metal oxides.The observed excellent catalytic activity was primarily attributed to the synergistic effect of carbon matrix adsorption and electron transfer from the multivalent Cu active site.The material exhibited suitability for a wide pH range（3.0-11.0）and could be regenerated through thermal activation,with essentially complete recovery of performance after regeneration.The reactive oxygen species in the Cu-Cu_xO@C/PDS system were identified and analysed by quenching experiments and ESR.The results showed that the reactive oxygen species produced by the system were·OH,SO₄·^-,O₂·^-and ¹O₂,with·OH and SO₄·^-produced by Cu⁺activation of S₂O₈^2-playing a major role in the degradation of phenol.（3）To address the problems of ion leaching and poor cycling stability of nano-metal oxide catalysts,a cobalt oxide-doped graphitized carbon as the shell and copper oxide nanoparticles as the core in a multi-active site core-shell structure（Cu/Co@C）was constructed by immobilizing cobalt ions through the Cu-BTC topological cage structure and using Co/Cu-BTC as a self-sacrificing template for phenol degradation.The Cu/Co@C-5/PMS system removed 100%phenol within 3 minutes and had excellent recyclability,maintaining 100%removal efficiency after three cycle tests.The leaching of copper and cobalt was reduced by 235and 134 times respectively compared to other Cu/Co ratio materials.The superior catalytic performance of the Cu/Co@C composite can be explained by its ability to facilitate electron transfer between the graphite structure and the cobalt-copper bimetal.Specifically,the composite enhances the redox performance of the metal active site by leveraging the potential difference between copper and cobalt,and modulates the spatial arrangement of the graphitized carbon layer structure through cobalt doping to strengthen the electron transfer capability of the carrier.The quenching experiments and ESR results indicated that O₂·^-and ¹O₂ were the main active oxygen species for the degradation of phenol in the Cu/Co@C-5/PMS system.（4）The catalytic performance of Cu-Cu_xO@C and Cu/Co@C in different oxidant systems was compared to investigate the effect of interfering factors（oxidant species,co-existing anions,organic pollutant species）on the degradation performance,and the catalytic degradation performance of different catalytic systems in simulated organic wastewater was explored.The results indicated that Cu/Co@C/PMS system was better than Cu/Co@C/PDS system had higher organic degradation efficiency.In Cu/Co@C/PDS system,the degradation efficiency of phenol with gradually decreased with increasing cobalt content.The Cu/Co@C/PMS system shown strong resistance to ion interference,and could completely degrade catechol and tetracycline within 30 minutes.In the experiment of simulating organic wastewater,the degradation rates of Cu/Co@C/PMS system for phenol,catechol and tetracycline were 87.2%,95.0%and 91.2%,respectively.The mineralization rate of organic reaches 67.5%.The response surface modeling was conducted for the three critical factors in Cu/Co@C/PMS system.The order in which operating parameters influence organic degradation performance is as follows:PMS dosage≥material dosage>solution pH.The model predictions further demonstrate that the Cu/Co@C/PMS system has the advantages of wide pH applicability,high catalytic activity and well recycling stability.90 Figures,18 Tables and 252 References...