Hydrolysis of 1,4-Butanediol-Derived Polyesters Into Tetrahydrofuran and Dicarboxylic Acids Over Lewis Acidic Ionic Liquids.

Chemical transformation of discarded polyesters into high-value chemicals is of great significance for advancing circular economy and sustainable development. Herein, we report a facile and efficient strategy for one-pot conversion of 1,4-butanediol-based polyesters (BDPs) via equivalent water hydrolysis. The reaction is achieved over 1-butyl-3-methyl-imidazolium chloride-ZnCl2-based ionic liquids ([BMIm][ZnnCl2n + 1]) under mild conditions (e.g., 120 °C), producing tetrahydrofuran (THF) and corresponding dicarboxylic acids. Among the designed ionic liquids, [BMIm][Zn4Cl9] showed the optimal catalytic performance, affording dicarboxylic acids and THF in excellent yields. Moreover, the catalyst possesses excellent recyclability and can be reused for five consecutive runs without obvious activity attenuation. Mechanism investigation endorses that BDPs are first hydrolyzed to generate acyloxyl alcohol intermediates, which are further converted into THF and dicarboxylic acids through ring-closing C─OH/C─O metathesis under the cooperation of cation-anion pairs in the ionic liquid catalyst. This work establishes a simple, green, and novel protocol for the selective degradation and valorization of BDPs, holding great potential for practical industrial applications.