Hierarchical NH2-MIL-88B(Fe)-derived Fe3O4@porous carbon/g-C3N4 nanocomposite for magnetically recoverable visible light photocatalysis of azo dyes

Martin  Osemba; Loice  Ojwang; Adrián  Huerta; Samuel  Karenga; Godffrey Keru

doi:10.5564/mjc.v27i56.5389

Authors

Dr. Martin Ouma Osemba Department of Natural Sciences, Mount Kenya University, Thika 342-01000, Kenya https://orcid.org/0009-0007-2045-4746
Dr. Loice Ojwang Department of Mathematics, Statistics and Physical Sciences, School of Science and Informatics, Taita Taveta University, Voi 635-80300, Kenya https://orcid.org/0000-0001-8339-6618
Dr. Adrián Chávez Huerta Research and Development Division, Zulian Institute of Technological Research Foundation, La Cañada de Urdaneta, Zulia 4033, Venezuela https://orcid.org/0000-0002-5094-4478
Dr. Samuel Karenga Department of Natural Sciences, Mount Kenya University, Thika 342-01000, Kenya https://orcid.org/0009-0008-1562-383X
Dr. Godffrey Keru Department of Chemistry, Whitworth University, 300 W. Hawthorne Road, Spokane, WA 99251, USA https://orcid.org/0000-0002-4879-2196

Keywords:

NH₂-MIL-88B(Fe), Fe₃O₄@porous carbon, g-C₃N₄, photocatalysis, azo dyes, magnetic recovery, Z-scheme heterojunction

Abstract

A hierarchical Fe₃O₄@porous carbon/g-C₃N₄ nanocomposite was synthesized from NH₂-MIL-88B(Fe) through controlled pyrolysis and heterojunction assembly for visible-light photocatalytic degradation of azo dyes. Structural and optical characterization confirmed the formation of a porous heterostructure with enhanced visible-light absorption and charge separation. Under visible-light irradiation (λ > 420 nm), the composite achieved degradation efficiencies of 98.6% for methyl orange and 96.8% for Congo red within 90 min. The catalyst exhibited a saturation magnetization of 32.4 emu g⁻¹, enabling rapid magnetic separation within approximately 20 s. Radical trapping experiments indicated that •OH and •O₂^- were the dominant reactive species, supporting a Z-scheme charge-transfer mechanism. The nanocomposite retained 92.3% of its initial photocatalytic efficiency after five cycles, demonstrating good stability, reusability, and potential for sustainable wastewater treatment.

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References

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