Bicyclic Nitroxyl Mediated Biopolymer Degradation Under Mild Conditions
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초록
내용
Lignin represents a potential feedstock suitable to produce a high value-added substance, which used in the fields of monomer production, fine chemistry, and pharmaceuticals. This work reports the selective photocatalytic oxidation of lignin model compounds in organic dye-sensitized photoelectrochemical cells (ODSPECs) coupling with hydrogen atom transfer agents (HATs) co-catalyst. An organic dye 5-[4-(diphenylamino)phenyl]thiophene-2-cyanoacrylic acid (DN-F02) containing triphenylamine (TPA) donor as a photocatalyst was immobilized on mesoporous-TiO2 coated fluorine-doped tin oxide glass substrates (DN-F02/meso-TiO2/FTO). Photocatalytic oxidation of lignin decomposition at DN-F02/meso-TiO2/FTO photoanode was carried out in the presence of bicyclic nitroxyl co-catalyst (9-azabicyclo[3,3,1]nonan-3-one-9-oxyl, ABNO). This photoelectrocatalytic process with the ODSPECs incorporating a ABNO mediator was evaluated with a phenolic lignin model compound (LMC) under 1 sun illumination. Moreover, chemoselective fragmentation of CAryl─Cα bond in the LMC was observed at room temperature under the 1 sun illumination and characterized by 1H NMR, GC-FID, and GC-MS. This system can offer a unique strategy to perform selective C─O/C─O bond cleavage for real biopolymer or petroleum-based polymer degradation under mild conditions.