Visible-light driven photocatalytic degradation of tartrazine using Co@ZIF-8 monoliths
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Piwai Tshumaa, Arnold Phiria, Mercy Chaparadzaa, Thapelo Seimelab,
Mmantsae Dialeb, Nicola Vimbainashe Poshayia, Linia Gedi Marazania
and Gift Mehlanaa
a Midlands State University, Department of Chemical Sciences, Zimbabwe.
b Department of Physics, University of Pretoria, South Africa
Introduction: Metal–organic frameworks have emerged as promising materials for environmental remediation due to their high surface area, tunable porosity, and structural versatility. However, most reported MOF photocatalysts are synthesized as powders, which are prone to aggregation, and challenging to recover after use. Herein, monolithic cobalt-doped ZIF-8 was synthesized via a rapid sol–gel method for the degradation of tartrazine dye in aqueous solution. PXRD results confirmed the successful formation of the ZIF-8 framework with preservation of the sodalite topology after cobalt incorporation, while UV-Vis DRS revealed the emergence of visible-light absorption bands attributed to d–d transitions of tetrahedrally coordinated Co2+ ions. Tauc analysis indicated the presence of mid-gap electronic states (1.9 eV) associated with cobalt doping, enabling improved visible-light responsiveness. The Co@ZIF-8 monolith achieved 86.0 ± 1.6% degradation under optimal conditions (4 mg L−1, pH 5, 45 mg, 150 min), outperforming pristine ZIF-8 (42.8 ± 2.1%). Dark adsorption control showed 31.9 ± 1.9% removal, confirming dye concentration on the monolith surface prior to photocatalysis. Kinetic studies indicated pseudo-first-order behaviour, while reusability tests showed retained activity after five cycles, with PXRD confirming framework integrity. These findings highlight the potential of monolithic Co-doped ZIF-8 as a stable and reusable photocatalyst for the treatment of dye-contaminated wastewater.
Funding: Acknowledgements The author(s) declared that financial support was received for this work and/or its publication. This paper was funded as part of the Future Africa Research Leadership Fellowship (FAR-LeaF cohort II) Programme, a 2-year research-oriented fellowship programme, supported by the Andrew Carnegie Foundation, formerly Carnegie Corporation of New York (CCNY) (G-PS-2360692) and hosted at Future Africa, University of Pretoria.
Piwai Tshuma, Arnold Phiri, Mercy Chaparadza, Thapelo Seimela, Mmantsae Diale, Nicola Vimbainashe Poshayi, Linia Gedi Marazani, Gift Mehlana; Visible-light driven photocatalytic degradation of tartrazine using Co@ZIF-8 monoliths. RSC Adv. 2026; |
