Morphological variations of g-C 3 N 4 photocatalysts for the hydrogenolysis of lignin model compounds Raphaël Abolivier and James A. Sullivan School of Chemistry, University College Dublin, Dublin, Ireland Most chemical intermediates in the fine chemistry, pharmaceutical and fuel industries are currently produced via crude oil refining. Given the end-of-life mineralization of products made from these, this is a major source of atmospheric CO 2 release. The valorization of lignin via generation of aromatic platform compounds is one of the most attractive pathways to feed the different chemical industries with intermediates that are sourced in a greener manner 1 . The conversion of biomass (including lignin) through catalyzed thermal processes has been widely investigated and, whilst promising, it still suffers from undesired char formation as well as the need for high energy and (often unsustainable) H 2 (g). A more recent approach is the use of simulated solar light as a green energy source for the cleavage of bonds in lignin. The reactions are perfomed at room temperature and atmospheric pressure making the overall process much greener. Acetonitrile (CH 3 CN) is a solvent that can be easily photo-oxidized, generating hydrogen species (2 CH 3 CN à CNCH 2 CH 2 CN + H 2 ) 2 . It is therefore an ideal solvent candidate for the photocatalytic hydrogenolysis of lignin. Graphitic carbon nitride (g-C 3 N 4 ) is a cheap, wide band-gap photocatalyst 3 , which generates highly reducing photo-electrons upon photoexcitation ( i.e., very negative CBM vs NHE). However, the bulk semiconductor suffers from rapid exciton recombination rates, hindering its large-scale application in photocatalysis 4 . Figure 1. Post-synthesis protocol for the morphological modification of bulk g-C3N4 per Wang et al.5 Urea, thiourea and dicyanamide were used for the synthesis of g-C 3 N 4 . g-C 3 N 4 photocatalysts with different morphologies (nanosheets (2D); nanorods (1D) and quantum dots (0D)) were also synthetized through a post- synthesis modification protocol proposed by Wang et al . 5 (see Fig. 1). All the prepared photocatalysts were characterized using a wide variety of techniques and applied in the hydrogenolysis of two lignin model compounds (2-phenoxy-1-phenylethanol and benzyl phenyl ether). This study was aimed at attempting to understand the underlaying mechanism(s) responsible for the observed differences the between different variants of g-C 3 N 4 photocatalysts for the hydrogenolysis reaction. Acknowledgments The A2P CDT is supported by the Science Foundation Ireland (SFI) and the Engineering and Physical Sciences Research Council (EPSRC) under Grant No. 18/EPSRC-CDT/3582. References 1. S. Takkellapati, T. Li and M. A. Gonzalez, Clean Technol Environ Policy, 2018 , 7, 1615-1630 X. Zhou, X. Gao, M. Liu, M. et al.Nat Commun , 2022 , 13, 110-118H. 2. Meirou, G. Huiqin, Z. Zhenxing et al., Int. J. Environ. Res. Public Health , 2022 , 19 B. Akash, C. Mahendra, Chemosphere , 2022 , 297, 134190-134215 W. 3. Wanjun, Y. Jimmy C., S. Zhurui, C. Donald, G. Ting, Chem. Commun. , 2014 , 50, 10148-10150
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