Effect of copolymerization agents on the efficiency of carbon nitride photocatalysts for the selective synthesis of p-anisaldehyde

• g-C 3 N 4 materials obtained by copolymerization efficient for p -anisaldehyde synthesis. • Barbituric acid improved the photocatalytic performance of bulk g-C 3 N 4. • Combining copolymerization and thermal post-treatment increases aldehyde yields. • The best-performing catalyst proved to be highly stable after three catalytic runs. Graphite-like carbon nitride-based catalysts were prepared through the thermal copolymerization of dicyandiamide and organic compounds, namely barbituric acid, 2-aminobenzonitrile, and 2-aminothiophene-3-carbonitrile as copolymerization agents. The obtained materials were subjected to a thermal post-treatment at 500 °C. According to SEM micrographs, the addition of a copolymerization agent promotes the appearance of defects on the surface of bulk GCN due to the presence of nitrogen vacancies (revealed by XPS analyses). The thermal post-treatment resulted in an increased specific surface area due to the exfoliation of the pristine material. Materials were tested for the synthesis of p -anisaldehyde by photocatalytic oxidation of anysil alcohol under UV-LED irradiation. The materials prepared using barbituric acid as copolymerization agent presented enhanced activity compared to neat GCN, attributed to the high availability of nitrogen vacancies in the carbon nitride matrix. After 90 min of irradiation, the material produced with bartituric acid reached 93 % of anysil alcohol conversion and 89 % of yield towards p -anisaldehyde. After subjecting this material to a thermal post-treatment at 500 °C 98 % of conversion and 96 % of yield were obtained just after 30 min of reaction. The reusability tests performed with both catalysts proved their operational stability after three consecutive runs.