Post-synthetic modifications of graphitic carbon nitride for selective organic transformations Sebastiano Gadolini a† , Pau Farràs b and Elena Corbos a . a Johnson Matthey Technology Centre,Blounts Court Road, Reading, RG4 9NH,UK, b School of Chemistry, Ryan Institute, National University of Ireland, Galway H91 CF50, Ireland Johnson Matthey joined the UN Global Compact, a sustainability initiative for tackling societal challenges such as alternative energy, reducing chemical waste and access to life-saving molecules. Photochemistry, a branch of chemistry, is a promising way to convert and store solar energy. It relies on chemical processes that occur due to the absorption of light particles by semiconducting materials, generating an energy band gap. To run the process efficiently, the semiconductor's band gap must align with the redox potential of the application. Graphitic carbon nitrides (gCN) are promising hosts for heterogeneous photocatalysts because of their suitable and easy-to-tune band gap 1 . Furthermore, due to the aromatic structure and high nitrogen content, these compounds are ideal candidates for preparing (photo)catalysts based on metal nanoparticles or single atoms. Moreover, due to accessible amino-terminal groups, the gCN surface can be structurally modified to host molecular catalysts or organic molecules on its surface. This talk will compare the impact on the photocatalytic performances of graphitic carbon nitride by modifying its morphology and chemical composition before depositing or grafting metallic species both onto the surface and within the volume of gCN. It was previously demonstrated that the size and distribution of metals depend on the support composition and deposition methods. In this study, heteroatom doping with phosphorous has been evaluated to tune the optoelectronic properties of gCN 2 . E.g., it is known that phosphorous contains one more valence electron compared to carbon, thus by replacing C in the heptazine monomeric unit of gCN, four electrons covalently bond to the neighbouring N atoms adopting a planar structure, and the remaining electron delocalised into the conjugated system 3 . Thus, the interaction between metal-host is more robust due to the heteroatom, which introduces more electronegativity to the framework. In this research, the amount of dopant and metal loadings have been tuned for the deposition of palladium species, from clusters to atomic distributions 4 . Another strategy to tune the optoelectronic properties of gCN is to anchor transition metal complexes to its surface. In this work, Salen-type complexes have been designed to react with the amino-terminal groups of gCN. Thus, the final catalysts will have the advantages of both homogenous and heterogenous catalysts, such as high selectivity and easy recyclability. Finally, to test and compare the photoactivity of these materials, three model reactions have been chosen: photo- oxidative esterification of benzyl alcohol 5 , photo-epoxidation of olefins and hydrogen transfer reactions. References 1. T.S. Miller et al., Phys.Chem.Chem.Phys., 2017, 19, 15613 2. Z. Chen et al., ACS Sustainable Chem. Eng. 2019, 7, 5223−5230.
3. Z. Chen et al., ACS Nano, 2016, 10, 3166−3175. 4. Z. Chen et al., Adv. Funct. Mater. 2017, 27, 1605785 5. C. Wang et al., Journal of Catalysis, 2021, 393, 116–125
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