Facile synthesis of fumarate-type iron-cobalt bimetallic MOFs and its application in photo-Fenton degradation of organic dyes.

Water contamination from organic contaminants like dyes has wreaked havoc on the ecosystem and jeopardized people's health. To this end, in this experiment, the low-crystalline bimetallic MIL-88A Co/Fe-x (Co/Fe-x represents the Co/Fe molar ratio) was synthesized under mild conditions with fumaric acid as ligand, the best performing MIL-88A Co/Fe-2 can completely degrade the MB solution within 20 ​min (100 ​mL, 20 ​mg/L). At lower synthesis temperature, the morphology and coordination structure of MIL-88A(Fe) were greatly changed by the incorporation of Co2+, so that the bimetallic MIL-88A Co/Fe-2 had abundant unsaturated metal sites and oxygen defects. The photoelectrical tests found that the change of structure made the bimetallic MIL-88A Co/Fe-2 have a narrow band gap, photoresponsivity and electron-hole separation efficiency were all improved. Under simulated sunlight, MIL-88A Co/Fe-2 has good universal degradability to a variety of dyes (methyl violet, methyl orange, methylene blue, rhodamine B). In addition, the main active specie of MIL-88A Co/Fe-2 degrading organic dyes was investigated in this experiment, and the possible degradation mechanism was proposed, which provided a feasible idea for the development of efficient photo-Fenton catalysts. In this experiment, bimetallic MIL-88A Co/Fe with low crystallinity and high defects was synthesized by stirring method under mild conditions using fumaric acid as the organic ligand. The best performing MIL-88A Co/Fe-2 has good general degradability to various dyes (methyl violet, methyl orange, methylene blue, rhodamine B). Under mild conditions, the morphology and coordination structure of MIL-88A are greatly changed due to the incorporation of Co2+, which makes the bimetallic MIL-88A Co/Fe-2 rich in unsaturated metal sites and oxygen defects. Photo/electrochemical tests show that this structural change enables the bimetallic MIL-88A Co/Fe-2 to have a narrower band gap, and the photoresponse capability and electron-hole separation efficiency are both improved. [Display omitted] • Using fumaric acid as organic ligand, iron-cobalt bimetallic MIL-88A Co/Fe were prepared under mild conditions. • By reducing the synthesis temperature and introducing Co2+, the bimetallic MIL-88A Co/Fe-2 has a narrow band gap, and the photoresponse ability and electron-hole separation efficiency are improved. • Under simulated sunlight, MIL-88A Co/Fe-2 has good general degradation to various dyes (methyl violet, methyl orange, methylene blue, rhodamine B). [ABSTRACT FROM AUTHOR]