mpg-C₃N₄-Catalyzed Selective Oxidation of Alcohols Using O₂ and Visible Light

Abstract

Mesoporous carbon nitride (mpg-C(3)N(4)) polymer can function as a metal-free photocatalyst to activate O(2) for the selective oxidation of benzyl alcohols with visible light, avoiding the cost, toxicity, and purification problems associated with corresponding transition-metal systems. By combining the surface basicity and semiconductor functions of mpg-C(3)N(4), the photocatalytic system can realize a high catalytic selectivity to generate benzaldehyde. The metal-free photocatalytic system also selectively converts other alcohol substrates to their corresponding aldehydes/ketones, demonstrating a potential pathway of accessing traditional mild radical chemistry with nitroxyl radicals.

Bioinspired hollow semiconductor nanospheres as photosynthetic nanoparticles

“…The tri-s-triazine ring structure makes the polymer practically inert to chemical attacks (for example, acid, base, oxygen and organic solvents) and provides an appealing electronic structure as well as surface basicity 24 . These properties have already enabled its use for applications in the energy, catalysis and environmental fields, such as water splitting [25][26][27] , oxygen-reduction reactions 28,29 , selective hydrocarbon oxidation 30,31 , carbon dioxide activation 32 and pollutant control 33 . An improvement to these material functions once this earth-abundant organic semiconductor has been fabricated as a hollow nanostructure with controlled dimensions and surface functionalities can be predicted 34,35 .…”

Metal-Free Allylic Oxidation with Molecular Oxygen Catalyzed by g-C3N4 and N-Hydroxyphthalimide

“…The electrons in g-C 3 N 4 can be activated and transmit from valence band to conduction band under heating [32,33]. The superoxide radical anion (O 2 -) formed by molecular oxygen absorbing the excited electrons from the conduction band of the g-C 3 N 4 [22], captures a hydrogen from NHPI generating PINO. At the same time, the O 2 -forms HOO -which can oxidize another NHPI to PINO.…”

“…After the first oxidation reaction, the g-C 3 N 4 can be easily recovered simply by washing with 0.2 M NaOH [22] and then dried in a vacuum oven at 65°C overnight. Then, the obtained g-C 3 N 4 was used directly in subsequent reaction cycles and no obvious loss of its catalytic activity and selectivity were observed, as shown in Fig.…”

“…This material resembles the polymeric melamine and is regarded as the most stable allotrope of covalent carbon nitride solids at ambient conditions, owing to the fact that it is formed by the sp 2 hybridization of carbon and nitrogen generating the heptazine heterocyclic ring (C 6 N 7 ) unit, later that the rings are linked by edge N forming the Q conjugated graphitic layers [20]. Beyond that, g-C 3 N 4 exhibits good stability, ease of reusability, electronic and catalytic properties [21], which make it promising applications as heterogeneous metal-free catalysts for selective alcohol oxidation [22], coupling of amines [23], selective oxidation of primary carbon hydrogen bonds [21], and hydrogen evolution by splitting water [24]. Very recently, Li and co-workers [25] have applied g-C 3 N 4 assisted by N-hydroxy compounds in selective allylic oxidation with molecular oxygen under visible light irradiation.…”

Graphitic g-C3N4-WO3Composite: Synthesis and Photocatalytic Properties

“…However, the pure g-C 3 N 4 exhibits high recombination rate of its photogenerated electron-hole pair. 19 To solve these drawbacks, several strategies have been applied to modify g-C 3 N 4 such as preparation of g-C 3 N 4 in mesostructure 20 and combination of g-C 3 N 4 with other materials by doping or grafting. [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] The obtained materials showed an improvement in photocatalytic performance.…”