Environmentally Friendly Multicolor Bio-Based Dyes Synthesized through Amino Acids and Caffeic Acid

This study adheres to the principles of green chemistry and develops a sustainable dye preparation and textile dyeing pathways inspired by phenolamine chemistry. Yellow, blue, red, and green caffeic acid (CA)-amino dyes were synthesized via the spontaneous polymerization of bio-based caffeic acid with various amino acids, and these newly synthesized dyes were successfully applied to the dyeing of cotton fabrics, demonstrating excellent dyeing performance. The synthesis of dyes and the dyeing of cotton fabrics are both carried out under mild conditions and do not require the addition of harmful chemicals. Through the study of the correlation between the color and structure of CA-amino dyes, the results indicate that the color of the dyes is critically regulated by amino acid side-chain diversity, which modulates the electronic structure and conjugated systems of the generated benzopyridine dyes. Moreover, owing to the synergistic effects arising from multiple bond strengths, the dyed fabrics exhibited excellent wash fastness. In addition, the dyed fabrics demonstrated outstanding antibacterial activity and efficient UV protection. This study establishes a green and efficient strategy for dye preparation and fabrication of multifunctional colored textiles.