The implementation of energy-efficient and sustainable technologies for organic synthesis to reduce the ecological impact of important industrial routes has been a hot-topic in worldwide research. Traditional chemical industry requires the use of hazardous oxidants/reductants and harsh operation conditions, such as high temperature and pressure. In this scenario, photocatalytic synthesis processes have appeared as a promising route for the synthesis of fine chemicals by operating under mild conditions. Moreover, the possibility of being activated by natural energy sources, such as sunlight, or by low-energy consumption radiation sources such Light Emitting Diodes (LEDs) may contribute for reducing the energy costs of the process.
Selective conversion of aromatic alcohols to the corresponding aldehydes is considered an essential chemical transformation from the industrial point of view. The main challenges dealing with the photocatalytic synthesis of aromatic aldehydes are related to the development of efficient catalysts and appropriate reaction systems, seeking for maximized yield and selectivity .
In the present work, graphite-like carbon nitride (GCN) based materials were applied for the photocatalytic synthesis of several aromatic aldehydes namely, benzaldehyde (BAD), anisaldehyde (AAD), vanillin (VAD), piperonal (PAD) and 4-tolualdehyde (TAD). Due to several practical problems arising from the use of catalyst suspensions, C3N4 nanosheets were successfully immobilized in glass Raschig rings and polyester fabrics, avoiding the costs related to catalysts separation and enabling continuous operation. A comparison between conventional batch and continuous flow photocatalytic reactors was evaluated.
Acknowledgements. This work was financially supported by Associate Laboratory LSRE-LCM - UIDB/50020/2020 of the Associate Laboratory LSRE-LCM - funded by national funds through FCT/MCTES (PIDDAC) and by projects POCI-01-0145-FEDER-031268 and POCI-01-0145-FEDER-030674, funded by European Regional Development Fund (ERDF) through COMPETE2020 - Programa Operacional Competitividade e Internacionalização (POCI) – and by national funds through FCT - Fundação para a Ciência e a Tecnologia.
 J.C. Lopes, M.J. Sampaio, R.A. Fernandes, M.J. Lima, J.L. Faria, C.G. Silva, Catalysis Today, (2019), DOI: 10.1016/j.cattod.2019.03.050 , in press.