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From: Selective ROS-mediated oxidative depolymerization of lignin to guaiacyl monomers over a mesoporous Cu₂Fe₁/JN catalyst

Selective ROS-mediated oxidative depolymerization of lignin to guaiacyl monomers over a mesoporous Cu<sub>2</sub>Fe<sub>1</sub>/JN catalyst

Figure 3. Mechanistic insights into ROS-mediated oxidative depolymerization of calcium lignosulfonate over Cu₂Fe₁/JN. (A) Time-dependent UV-vis spectra of TMB oxidation; (B) EPR spectra of DMPO-trapped ROS; (C) Molecular electrostatic potential surfaces of 2-phenoxy-1-phenylethanol and 2-phenoxy-1-phenylethanone; (D) Proposed catalytic oxidation pathway of 2-phenoxy-1-phenylethanol; (E) FTIR spectra of calcium lignosulfonate before oxidation (upper) and after oxidation (lower); (F and G) Time-dependent UV-vis spectra of calcium lignosulfonate during oxidative depolymerization and the corresponding 2D contour plot; (H and I) Three-dimensional FTIR spectra of calcium lignosulfonate during oxidative depolymerization, and the corresponding 2D plot; (J) The profiles of five selected characteristic peaks (the signal intensities were directly obtained from the instrument and exported for plotting). BDE: Bond dissociation energy; ROS: reactive oxygen species; TMB: 3,3′,5,5′-tetramethylbenzidine; EPR: electron paramagnetic resonance; DMPO: 5,5’-dimethyl-1-pyrroline N-oxide; FTIR: Fourier-transform infrared.