Mechanistic DFT Insights into Biomimetic Mn-Porphyrin Catalysts for Peroxymonosulfate-Driven Degradation of Carbamazepine in Water
- 1Center of Excellence in Environmental Studies, King Abdulaziz University, Jeddah 21589, Makkah, Saudi Arabia
- 2Department of Marine Biology, Faculty of Marine Sciences, King Abdulaziz University, Jeddah 21589, Makkah, Saudi Arabia
- 3Department of Biological Sciences, Faculty of Science, King Abdulaziz University, Jeddah 21589, Makkah, Saudi Arabia
Abstract
One of the most recalcitrant and environmentally persistent micropollutants detected worldwide in surface waters, groundwater, and treated effluents at concentrations ranging from ng L−1 to µg L−1 is carbamazepine (CBZ), a commonly prescribed anticonvulsant and mood-stabilizing drug. Conventional wastewater treatment technologies are not effective in removing CBZ; therefore, advanced remediation strategies are required for its complete mineralization. Herein, we present a detailed mechanistic study of the oxidation of CBZ by Mn(III) meso-tetraphenylporphyrin (Mn-TPP) in the presence of peroxymonosulfate (PMS) using the spin-unrestricted density functional theory (DFT) at the Becke, 3-parameter, Lee–Yang–Parr (B3LYP-D3BJ) level of theory with dispersion corrections. The full free energy profiles of catalysis were constructed by optimizing the geometries using the LACVP basis set on Mn and the 6-31G(d,p) basis set on all other non-metal atoms, followed by single-point calculations at the 6-311 + G(d,p) level with the SMD implicit solvation model to mimic the aqueous environment. The data suggest that the oxidation of Mn-TPP by PMS to form the key high-valent intermediate [Mn(V)=O(TPP)] + is thermodynamically and kinetically feasible. The activation barrier for PMS-mediated formation of [Mn(V)=O(TPP)]+ is ΔG‡ = 17.8 kcal mol−1 (SMD water, 298 K), indicating kinetic accessibility under ambient conditions. CBZ subsequently oxidizes the dibenzazepine ring system via concerted radical and non-radical mechanistic pathways. The computed ET pathway has an activation barrier of ΔG‡ = 16.4 kcal mol−1 and a strongly exergonic reaction free energy (ΔGr = −47.3 kcal mol−1). Analysis of the transition state shows that the spin density is localized on the Mn-Oxo unit and adjacent porphyrin π-system, characteristic of Mn-oxo species and consistent with the computed preference for the ET pathway over the OAT pathway on the examined spin surface. These mechanistic insights provide quantitative, molecular-level design parameters to rationally optimize next-generation porphyrin-based quantum catalysts for persistent pharmaceutical contaminant remediation.
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BibTeX
@article{oves2026mechanistic,
title = {{Mechanistic DFT Insights into Biomimetic Mn-Porphyrin Catalysts for Peroxymonosulfate-Driven Degradation of Carbamazepine in Water}},
author = {Mohammad Oves and Muhammad B. Alim and Sivaraman Chandrasekaran and Huda A. Qari and Majed Ahmed Al-Shaeri},
journal = {Catalysts},
year = {2026},
month = oct,
doi = {10.3390/catal16110963},
url = {https://www.mdpi.com/2073-4344/16/11/963},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Mechanistic DFT Insights into Biomimetic Mn-Porphyrin Catalysts for Peroxymonosulfate-Driven Degradation of Carbamazepine in Water
AU - Mohammad Oves
AU - Muhammad B. Alim
AU - Sivaraman Chandrasekaran
AU - Huda A. Qari
AU - Majed Ahmed Al-Shaeri
PY - 2026
DA - 2026/10/28
JO - Catalysts
DO - 10.3390/catal16110963
UR - https://www.mdpi.com/2073-4344/16/11/963
AB - One of the most recalcitrant and environmentally persistent micropollutants detected worldwide in surface waters, groundwater, and treated effluents at concentrations ranging from ng L−1 to µg L−1 is carbamazepine (CBZ), a commonly prescribed anticonvulsant and mood-stabilizing drug. Conventional wastewater treatment technologies are not effective in removing CBZ; therefore, advanced remediation strategies are required for its complete mineralization. Herein, we present a detailed mechanistic study of the oxidation of CBZ by Mn(III) meso-tetraphenylporphyrin (Mn-TPP) in the presence of peroxymonosulfate (PMS) using the spin-unrestricted density functional theory (DFT) at the Becke, 3-parameter, Lee–Yang–Parr (B3LYP-D3BJ) level of theory with dispersion corrections. The full free energy profiles of catalysis were constructed by optimizing the geometries using the LACVP basis set on Mn and the 6-31G(d,p) basis set on all other non-metal atoms, followed by single-point calculations at the 6-311 + G(d,p) level with the SMD implicit solvation model to mimic the aqueous environment. The data suggest that the oxidation of Mn-TPP by PMS to form the key high-valent intermediate [Mn(V)=O(TPP)] + is thermodynamically and kinetically feasible. The activation barrier for PMS-mediated formation of [Mn(V)=O(TPP)]+ is ΔG‡ = 17.8 kcal mol−1 (SMD water, 298 K), indicating kinetic accessibility under ambient conditions. CBZ subsequently oxidizes the dibenzazepine ring system via concerted radical and non-radical mechanistic pathways. The computed ET pathway has an activation barrier of ΔG‡ = 16.4 kcal mol−1 and a strongly exergonic reaction free energy (ΔGr = −47.3 kcal mol−1). Analysis of the transition state shows that the spin density is localized on the Mn-Oxo unit and adjacent porphyrin π-system, characteristic of Mn-oxo species and consistent with the computed preference for the ET pathway over the OAT pathway on the examined spin surface. These mechanistic insights provide quantitative, molecular-level design parameters to rationally optimize next-generation porphyrin-based quantum catalysts for persistent pharmaceutical contaminant remediation.
SN - 2073-4344
ER -