A bio-inspired strategy to enhance the photocatalytic performance of g-C3N4 under solar irradiation by axial coordination with hemin

- The system is a combination of photocatalysis and biomimetic catalysis.
- The catalytic activity of g-C3N4 and the stability of hemin were enhanced under solar irradiation.
- High-valent iron (Fe(IV) = O) species could be detected by ESI-MS and GC-MS.
- The final products of 4-CP were small molecule acids which were biodegradable.
- O2−, Fe(IV) = O, OOH species played the main role in g-C3N4-IMD-hemin/H2O2 system.

In nature, metalloporphyrins, such as chlorophyll, cytochrome P450 and so forth, are key materials in maintaining the ecological cycles, especially the carbon cycle, and play an important role in both photosynthesis and the catalytic oxidation of organisms. Inspired by these factors, we skillfully combined photocatalysis and biomimetic catalysis using imidazole (IMD)-functionalized modification of g-C3N4 and axial coordination with hemin. Compared with pure hemin, g-C3N4 and a mixture of the two, our novel catalytic system (g-C3N4-IMD-hemin/H2O2) showed high photocatalytic oxidation activity for the degradation of 4-chlorophenol (4-CP), and the stability of hemin was enhanced under solar irradiation. Furthermore, the effect of pH and the sustained photocatalytic oxidation stability of g-C3N4-IMD-hemin for degrading 4-CP were investigated. The results indicated that g-C3N4-IMD-hemin presents a high photocatalytic oxidation activity over a wide pH range and exhibits good recyclability. A series of designed experiments showed that superoxide radicals (O2−), high-valent iron (Fe(IV) = O) species, peroxy radicals (OOH) and few hydroxyl radicals (OH) were generated in the g-C3N4-IMD-hemin/H2O2 system. This synergistic photocatalytic and biomimetic process offers new insight for the utilization of solar energy and offers a new perspective for the exploration of catalysts for environmental remediation.

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