The Synthesis Of Bimetallic Zeolite Imidazole Ester Framework Material In Supercritical CO₂ And Its Application

As a new type of porous materials,zeolite imidazolate framework materials（ZIFs）have the characteristics of high porosity,large specific surface area,ordered and adjustable pore size.In this paper,Zn/Co-ZIFs containing zinc and cobalt were rapidly synthesized in supercritical carbon dioxide（sc-CO₂）,The Zn/Co-ZIFs were used as catalyst to activate peroxymonosulfates（PMS）and remove bisphenol A（BPA）from wastewater.Zn/Co-ZIFs were synthesized from Zinc acetylacetonate,cobalt acetylacetonate and 2-methylimidazole（2-Me Im）in sc-CO₂.It was found that pressure,temperature,the ratio of Zn and Co would affect the nucleation and development of the crystal.Finally,under the optimized reaction conditions,that is,at 30 MPa,70℃,n（Zn）:n（Co）:n（2-Me Im）=1:1:8,a series of Zn/Co-ZIF materials were synthesized in sc-CO₂ in 10minutes.The highest pyrolysis temperature of the product is 610℃,the specific surface area is 1788.11 m²/g.The material has a microporous structure and the pore size range is 2.15-2.37 nm.Compared with conventional methods,this method takes less time,avoids the use of organic solvents,and the resulting product has a higher pyrolysis temperature and a larger pore size,which is beneficial to be used as a good catalyst and carrier.The synthesized Zn/Co-ZIF was used as catalyst to activate PMS and remove BPA from wastewater.The results showed that when Zn₁Co₁-ZIF was used as catalyst,BPA concentration was 50 mg·L^-1,PMS concentration was 0.8 mM,and catalyst dosage was150 mg·L^-1,the removal of BPA rate was 89%,and this system could be applied to wastewater with the range of p H=5-9.After being recycled for three times,Zn₁Co₁-ZIF could still maintain the 91%removal rate of fresh catalyst,and Co²⁺escape concentration is far lower than the national standard.Through free radical quenching experiment and EPR test,it was found that the reaction process depends on the joint action of free radical and non free radical,and ¹O₂ plays the most significant part.At the same time,the probable degradation pathways of BPA were simulated based on the detected intermediate products.This study provides a green and efficient preparation process for the synthesis of Zn/Co-ZIF materials,and a new idea for the large-scale production of ZIF materials.At the same time,this study provides an efficient and stable catalyst for the removal of BPA from wastewater.