The development of efficient photocatalytic systems capable of harnessing visible light is critical for sustainable environmental remediation. In this study, a novel Z-scheme heterostructure—CeO₂/N-doped carbon/Ce-TCPP—was engineered through controlled partial thermal decomposition of cerium-based metal-organic frameworks (Ce-TCPP) under nitrogen atmosphere. The resulting composite integrates the advantages of multiple components: CeO₂ provides strong redox activity and oxygen vacancy sites; N-doped carbon enhances electron transfer and stabilizes charge carriers; and preserved Ce-TCPP maintains structural integrity and light-harvesting capability. This tripartite architecture enables effective spatial separation of photogenerated electrons and holes, significantly improving photocatalytic performance.
The synthesis began with the rapid microwave-assisted hydrothermal preparation of spindle-shaped Ce-TCPP MOFs, which were then subjected to low-temperature pyrolysis at 450 °C. Unlike full decomposition, this mild treatment preserved a portion of the original framework while converting the rest into CeO₂ and N-doped carbon. XRD analysis confirmed the presence of CeO₂ crystallites without dominant peaks from Ce-TCPP, indicating partial transformation. HR-TEM revealed well-defined lattice fringes corresponding to the (111) plane of CeO₂ (d = 0.31 nm), while elemental mapping showed uniform distribution of C, Ce, N, and O across the spindle-like structures. Notably, Ce and O concentrations were higher in certain regions, confirming localized formation of CeO₂ nanoparticles embedded within the carbon matrix.
XPS data further validated the chemical evolution during pyrolysis. The C 1s spectrum shifted toward lower binding energy, reflecting the conversion of organic functional groups into graphitic carbon. The N 1s peak at 397.9 eV intensified, suggesting the transformation of pyrrolic nitrogen into more stable graphitic nitrogen species. Meanwhile, the O 1s signal decreased at 531.8 eV (carboxylic groups) and increased at 533.2 eV (Ce–O bonds), consistent with linker degradation and oxide formation. A new Ce⁴⁺ peak emerged at 917.3 eV, confirming oxidation of Ce³⁺ to Ce⁴⁺ during heating. These results collectively indicate that the material consists of a hybrid system comprising CeO₂ nanocrystals, N-doped carbon, and partially intact Ce-TCPP units.
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**Mechanism of Enhanced PMS Activation via Z-Scheme Charge Transfer**
The exceptional catalytic performance of CeO₂/NC/Ce-TCPP-450 stems from its unique Z-scheme charge transfer mechanism. Based on UV-Vis DRS and UPS measurements, the band gap of Ce-TCPP was estimated at ~2.AXIN1 Antibody manufacturer 25 eV, while CeO₂ exhibited a wider band gap (~2.67 eV). The valence band maximum (VBM) of CeO₂ (+3.06 eV vs NHE) is more positive than that of Ce-TCPP (+2.07 eV), allowing photogenerated holes in CeO₂ to directly oxidize surface hydroxyl groups (OH⁻) to generate highly reactive •OH radicals under visible light irradiation.
Simultaneously, electrons excited in the conduction band (CB) of CeO₂ migrate to the N-doped carbon layer due to favorable energy alignment. From there, they recombine with holes in the valence band (VB) of Ce-TCPP, effectively separating electrons from Ce-TCPP and holes from CeO₂. This process suppresses charge recombination and extends carrier lifetime. The N-doped carbon acts as an electron mediator and also serves as an active site for PMS activation, facilitating the generation of sulfate radicals (SO₄⁻). The synergistic interplay between these components results in a powerful oxidative system driven by visible light.
PL and TRPL spectra provided direct evidence of this mechanism. The CeO₂/NC/Ce-TCPP-450 sample displayed the lowest fluorescence intensity and the longest decay lifetime (14.9 ns), surpassing both pure CeO₂ (9.3 ns) and Ce-TCPP (10.5 ns). This indicates minimal radiative recombination and efficient charge separation, confirming the formation of a Z-scheme system. Moreover, ESR measurements using DMPO and TEMPO spin traps clearly detected •OH and SO₄⁻ signals only when the catalyst was combined with PMS under illumination—further validating the radical-driven degradation pathway.ASK1 Antibody Epigenetic Reader Domain
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**High Efficiency in Degradation of Organic Pollutants Under Ambient Conditions**
The CeO₂/NC/Ce-TCPP-450 catalyst demonstrated outstanding efficiency in degrading various recalcitrant pollutants under visible light.PMID:33975303 For rhodamine B (RhB, 10 mg/L), over 99% removal was achieved within 20 minutes with the assistance of PMS. Even at low catalyst loading (5 mg/L), the system achieved rapid mineralization—65% of total organic carbon (TOC) was converted to CO₂ and H₂O. Similar high performance was observed for other contaminants: methylene blue (MB, 98.6%), methyl orange (MO, 94.4%), tetracycline (TCL, 84.5%), and oxytetracycline (OTC, 97.8%) all reached >94% degradation within one hour.
The reaction kinetics followed pseudo-first-order behavior, with rate constants increasing significantly when visible light was introduced. The enhancement factor was particularly pronounced compared to dark conditions or single-component systems. Furthermore, the catalyst maintained excellent stability over five consecutive cycles, with only slight decline in activity. Post-reaction characterization via XRD, SEM, TEM, and XPS revealed no significant changes in crystal structure, morphology, or chemical composition. The Ce leaching level remained below 37 ppb (ICP-MS), well below permissible limits, confirming the robustness and safety of the material.
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**Environmental and Practical Implications of MOF-Derived Heterogeneous Catalysts**
This work highlights the potential of MOF-derived materials as next-generation heterogeneous catalysts for advanced oxidation processes (AOPs). By leveraging partial thermal decomposition instead of complete carbonization, the strategy preserves key functional moieties while introducing beneficial phases like CeO₂ and N-doped carbon. This approach balances structural integrity with enhanced catalytic activity, offering a tunable platform for designing multifunctional materials.
Compared to traditional methods involving UV irradiation, heat, or toxic catalysts, this visible-light-driven system operates under ambient conditions with low energy input and minimal secondary pollution. The use of earth-abundant elements (Ce, C, N) enhances sustainability, while the facile synthesis method allows scalability. The ability to degrade diverse pollutants—including dyes and antibiotics—underscores its broad applicability in real-world wastewater treatment.
Moreover, the mechanistic insights gained here provide a blueprint for future catalyst design. The Z-scheme architecture can be extended to other MOF-metal oxide-carbon systems, enabling rational engineering of charge transfer pathways. Future work may explore integration with membrane filtration or solar reactors for practical deployment in decentralized water purification systems.
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**Conclusion and Outlook**
In summary, this study successfully developed a high-performance Z-scheme photocatalyst—CeO₂/N-doped carbon/Ce-TCPP—through controlled pyrolysis of Ce-TCPP MOFs. The material exhibits exceptional visible-light responsiveness, enabling efficient activation of peroxymonosulfate for the degradation of persistent organic pollutants. The synergy between CeO₂, N-doped carbon, and residual Ce-TCPP creates a charge-separated system that maximizes radical generation and minimizes recombination. With high stability, low metal leaching, and broad substrate compatibility, this catalyst represents a significant advancement in MOF-based environmental technologies.
Future research will focus on optimizing the pyrolysis protocol for industrial-scale production, exploring the system’s performance in real wastewater matrices, and integrating it into modular reactor designs. Ultimately, such smart, sustainable materials hold great promise for addressing global water contamination challenges through clean, solar-powered remediation.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com