Metal‐Free and Heterogeneous Photocatalytic Reduction of 4‐Nitroaniline by a Poly(Ethylene Glycol)‐Supported Eosin Dye under Visible‐Light Exposure

Abstract

A new feasible approach for the photoreduction of a chemical pollutant, 4‐nitroaniline, to p‐phenylenediamine was developed. We highlighted the crucial roles of a polymer backbone and the atmosphere for the efficient heterogeneous reduction of 4‐nitroaniline. The novel synthesized poly(ethylene glycol)‐derived film containing immobilized eosin dye revealed a high photoreduction rate of 4‐nitroaniline. According to laser flash photolysis results the first step of this photoinduced process represents a single electron transfer from eosin radical anion to the 4‐nitroaniline to form a nitroaniline radical anion. The in‐situ electron paramagnetic resonance spin‐trapping experiments evidenced the generation of superoxide radical anion serving as catalyst in the p‐phenylenediamine production according to a photoreduction process. The main roles play by poly(ethylene glycol) matrix as efficient reducing agent and hydrogen‐donor molecule was also pointed out. A mechanism was proposed to explain the heterogeneous photoreduction of 4‐nitroaniline to p‐phenylenediamine in the presence of eosin dye‐based poly(ethylene glycol) system under air.

Direct Z-scheme α-MnO2@MnIn2S4 hierarchical photocatalysts with atomically defined junctions for improved photocatalytic activities

“…The 4-phenylenediamine (4-PDA) is a widely used industrial chemical raw material. It can be used in the preparation of azo dyes, as well as in the preparation of developers, rubber antioxidants, and copper-iron indicators [4][5][6][7][8] . The industrial preparation of 4-PDA is mainly prepared by using 4-nitroaniline (4-NA) as raw material and adopting industrial hydrogenation 9,10 .…”

Mechanistic Insight into the Light-Triggered CuAAC Reaction: Does Any of the Photocatalyst Go?

“…In photocatalyzed processes, evaluating the kinetics of excited states is crucial to postulate a plausible mechanism. , However, little attention has been paid to the exploration of the mechanism behind the light-triggered CuAAC. Only in a few cases, the fundamental aspects and molecular bases of such mechanism have been investigated through kinetics and spectroscopic methods, namely, laser flash photolysis (LFP), Fourier-transform infrared spectroscopy (FTIR), electron paramagnetic resonance (EPR), , or single-molecule spectroscopy …”