Sunlight Assisted Photocatalytic Valorization of Lignin Using Recyclable Light Harvesters

Abstract

The abundant aromatic supply lignin, which is generated from agri-biomass, can be used as a sustainable alternative for several platform chemicals and fuels. The strongly cross-linked and randomly polymerized structure of lignin makes it difficult to valorize. In the current work, we have developed a solar photocatalytic system based on porphyrin that can directly depolymerize lignin and lignin-model compounds. The porphyrin has been evaluated for photophysical characteristics such as singlet oxygen and fluorescence quantum yields. The developed catalyst has been initially utilized for the degradation of lignin model compounds and then directly on lignin. For assessment, the degraded lignin various characterization techniques such as UV−vis spectroscopy, heteronuclear single quantum coherence spectroscopy (HSQC), electron paramagnetic resonance (EPR), mass spectroscopy, and gel permeation chromatography (GPC) were used. Later, a plausible mechanism for the breakdown of lignin/lignin model compounds was inferred after the developed photocatalytic system was investigated under a variety of experimental conditions. The photocatalyst's recovery and recyclability were further evaluated. This solar-assisted photocatalytic valorization of lignin driven by the light harvesters is a smart and sustainable initiative to synergize agri-waste removal and platform chemical generation.

Design and Synthesis of Metalloporphyrin Nanoconjugates for Dual Light-Responsive Antimicrobial Photodynamic Therapy

“…One of the major purpose of the conjugation of metalloporphyrin to the nanocomposites is to enhance the photoactivation capability and visible light excitation. In this respect, the singlet oxygen generation efficiency (SOQY, Φ Δ ) of all the probes was calculated via a reported protocol using diphenylisobenzofuran (DPBF) as a singlet oxygen quencher . Upon generation of singlet oxygen, DPBF undergoes a 1,4-addition reaction to give endoperoxide, which further degrades to give 1,2- dibenzoyl benzene.…”

“…Briefly, the stock solution of metalloporphyrin, ZnO nanocomposites, nanoconjugates, and DPBF was prepared in DMSO (1 mg/mL). Further, the prepared stock solution of metalloporphyrin (5 μL) was added into the cuvettes containing 5 μL of DPBF solution, and volume was maintained up to 1 mL using DMSO (in the dark) . Moreover, the same procedure was followed for nanocomposites and nanoconjugates.…”