Abstract
Solar-driven photocatalysis has attracted significant attention in water splitting, CO2 reduction and organic synthesis. The syntheses of valuable azo- and azoxyaromatic dyes via selective photoreduction of nitroaromatic compounds have been realised using supported plasmonic metal nanoparticles at elevated temperatures (≥90 °C); however, the high cost, low efficiency and poor selectivity of such catalyst systems at room temperature limit their application. Here we demonstrate that the inexpensive graphitic C3N4 is an efficient photocatalyst for selective syntheses of a series of azo- and azoxy-aromatic compounds from their corresponding nitroaromatics under either purple (410 nm) or blue light (450 nm) excitation. The high efficiency and high selectivity towards azo- and azoxy-aromatic compounds can be attributed to the weakly bound photogenerated surface adsorbed H-atoms and a favourable N-N coupling reaction. The results reveal financial and environmental potential of photocatalysis for mass production of valuable chemicals.
Highlights
Solar-driven photocatalysis has attracted significant attention in water splitting, CO2 reduction and organic synthesis
By tuning the irradiation wavelength of the light sources, we have further demonstrated the versatility of the graphitic C3N4 (g-C3N4) catalyst for controlled photoconversion of various nitroaromatic compounds into their corresponding azoxy- or azo-compounds (Table 2)
We propose that the excellent performance of the g-C3N4 photocatalyst for nitrobenzene photoreductions can be associated with the efficient utilisation of photogenerated
Summary
Solar-driven photocatalysis has attracted significant attention in water splitting, CO2 reduction and organic synthesis. We show that both azoxybenzene and azobenzene can be synthesised by photoreduction of nitrobenzene with high selectivity using the cheap graphitic C3N4 (g-C3N4,
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