Selective Production of Benzaldehyde Using Metal‐Free Reduced Graphene Oxide/Carbon Nitride Hybrid Photocatalysts

Abstract

Benzyl alcohol was selectively oxidized to benzaldehyde in aqueous solution, at ambient conditions of temperature and pressure, by using a photocatalytic approach, with two types of irradiation sources, namely monochromatic UV−A light (392 nm) and visible light (400‐700 nm). Conversion after 4 h of reaction was more efficient under UV than under visible, with selectivity in excess of 80% for both irradiating sources. Composites of graphitic carbon nitride (g‐C3N4) containing small amounts of reduced graphene oxide (rGO) (up to 1 wt.%) were used as photocatalysts. The presence of rGO was confirmed by spectroscopic and microscopic analyses. Results show that small amounts of rGO phase can considerably enhance the photocatalytic activity of g‐C3N4 based catalysts, the best load being 0.10 wt.%. This improvement is attributed to the critical modification of morphological and electronic properties provided by the presence of rGO.

Visible Light-Induced Aerobic Oxidative Dehydrogenation of C–N/C–O to C=N/C=O Bonds Using Metal-Free Photocatalysts: Recent Developments

“…Similarly, graphene oxide-based promoters have demonstrated good activity in the oxidation of aromatic and aliphatic alcohols leading to the corresponding carbonyl products 69 when irradiated with visible light. In this sense, this reaction was performed well using a graphene oxide/carbon nitride hybrid material [210] and a surface-modified graphene oxide with TPP (GO-TPP40, 94) (Figure 28) [211], being able to recycle the last one by dispersion in H 2 O and sonication for 1 h with a decrease in its activity in the fourth cycle. Similarly, graphene oxide-based promoters have demonstrated good activity in the oxidation of aromatic and aliphatic alcohols leading to the corresponding carbonyl products 69 when irradiated with visible light.…”

Organocatalysis with carbon nitrides

“…The conversion of BA and product selectivity was considerably low due to the overlap between LED emission and photocatalyst absorption being smaller. On the other hand, the remaining visible irradiation (450–700 nm) can photo-excite the rGO phase, and as the energy levels of the CN T conduction band and rGO excited state are similar, the thermodynamic barrier to e – transfer was negligible and the photogenerated e – /h + pairs were stabilized by back electron donation (from rGO to CN T conduction band), thus creating reactive holes on the rGO surface which was available for the selective oxidation of BA [ 154 ]. Fernandes et al synthesized defect-induced 3-dimensional g-CN employing DCDA precursor, silica template via hard-templating route resulting in high specific surface area materials.…”

Heterogeneous Photocatalytic Organic Transformation Reactions Using Conjugated Polymers-Based Materials

“…Since the report on the selective oxidation of benzyl alcohol to benzaldehyde over mpg-C 3 N 4 under visible light irradiation reported by Wang’s group, much attention has been paid to conjugated polymer-based photocatalysts. Increasing numbers of photocatalysts for the selective oxidation of benzyl alcohol have been reported, − such as g-C 3 N 4 loaded with various metals, , Fe 2 O 3 /g-C 3 N 4 , CdS/g-C 3 N 4 and CTF-Th@SBA-15, which are summarized in Table .…”