Efficient catalysis of H2O2 with ionic liquid molecules to generate hydroxyl radicals and application in green chemistry cotton processes

Abstract

Among the materials used in biomass processing techniques, ionic liquids (ILs) are found to be more efficient and environmentally friendly, especially in terms of lignin and cellulose dissolution. However, designing IL molecules and applying them to green chemical processes at low temperatures also remains a grand challenge. Here, we design and fabricate two IL molecules containing an extended benzene ring conjugated system. Surprisingly, the IL molecules can efficiently catalyze H₂O₂ to produce ˙OH radicals at room temperature and very low concentrations, and also improve the dissolution of lignin in cottonseed hulls and the swelling of cotton fiber. There are strong interactions between the IL molecules with an extended π-conjugated system and cellulose/lignin macromolecules verified via density functional theory (DFT) calculations. The activation energy of the hydrogen peroxide reaction is appreciably reduced by generating free radicals with the catalysis of the IL molecules. The IL/H₂O₂ system was used in cotton cold pad-batch bleaching. Cotton fabric can be scoured and bleached at room temperature via one step, saving a lot of energy and chemicals. The green chemical processes catalyzed by the IL molecules afford enormous advantages in energy saving and efficiency improvement.