Issue 10, 2023

Solar energy driven C–C bond cleavage in a lignin model compound with a D–π–A organic dye-sensitized photoanode

Abstract

The high bond dissociation energy of C–C σ-bonds presents a challenge to chemical conversions in organic synthesis, polymer degradation, and biomass conversion that require chemoselective C–C bond cleavage at room temperature. Dye-sensitized photoelectrochemical cells (DSPECs) incorporating molecular organic dyes could offer a means of using renewable solar energy to drive these types of energetically demanding chemoselective C–C bond cleavage reactions. This study reports the solar light-driven activation of a bicyclic aminoxyl mediator to achieve C–C bond cleavage in the aryl-ether linkage of a lignin model compound (LMC) at room temperature using a donor–π-conjugated bridge–acceptor (D–π–A) organic dye-based DSPEC system. Mesoporous TiO2 photoanode surfaces modified with 5-[4-(diphenylamino)phenyl]thiophene-2-cyanoacrylic acid (DPTC) D–π–A organic dye were investigated along with a bicyclic aminoxyl radical mediator (9-azabicyclo[3,3,1]nonan-3-one-9-oxyl, KABNO) in solution with and without the presence of LMC. Photophysical studies of DPTC with KABNO showed intermolecular energy/electron transfer under 1 sun illumination (100 mW cm−2). Under illumination, the D–π–A type DPTC sensitized TiO2 photoanodes facilitate the generation of the reactive oxoammonium species KABNO+ as a strong oxidizing agent, which is required to drive the oxidative C–C bond cleavage of LMC. The photoelectrochemical oxidative reaction in a complete DSPEC with KABNO afforded C–C bond cleavage products 2-(2-methoxyphenoxy)acrylaldehyde (94%) and 2,6-dimethoxy-1,4-benzoquinone (66%). This process provides a first report utilizing a D–π–A type organic dye in combination with a bicyclic nitroxyl radical mediator for heterogeneous photoelectrolytic oxidative cleavage of C–C σ-bonds, modeled on those found in lignin, at room temperature.

Graphical abstract: Solar energy driven C–C bond cleavage in a lignin model compound with a D–π–A organic dye-sensitized photoanode

  • This article is part of the themed collection: Biorefining

Supplementary files

Article information

Article type
Paper
Submitted
15 2 2023
Accepted
16 3 2023
First published
16 3 2023

Sustainable Energy Fuels, 2023,7, 2339-2348

Author version available

Solar energy driven C–C bond cleavage in a lignin model compound with a D–π–A organic dye-sensitized photoanode

S. Kim, H. C. Kang, C. Chu, S. Li, K. Yoo, U. K. Wijethunga, W. Zheng, C. G. Yoo, B. D. Sherman, J. Lee and G. Leem, Sustainable Energy Fuels, 2023, 7, 2339 DOI: 10.1039/D3SE00194F

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