Rational Design of a Ternary Hybrid Catalyst Breaking the Activity–Stability Trade-Off in Levulinic Acid Esterification to Ethyl Levulinate

The esterification of levulinic acid with ethanol to produce ethyl levulinate represents a promising biomass valorization route, yet solid acid catalysts are constrained by an inherent trade-off between activity and stability. Herein, we report a rationally designed HPW 10 @UiO-66/PIL ternary hybrid catalyst that overcomes this long-standing dilemma. The catalyst is constructed by confining phosphotungstic acid clusters within a poly(ionic liquid)s network anchored to defect-engineered UiO-66, enabling synergistic electrostatic and hydrogen-bonding stabilization. Under optimized conditions (LA/EtOH molar ratio = 1:6.8, 70 °C, 6 h), the catalyst achieved an exceptional ethyl levulinate yield of 98.4% with 99% selectivity. ICP analysis confirmed negligible HPW leaching (<0.5 wt %) during the reaction. The catalyst retained 97% of its initial yield after five cycles, demonstrating superior recyclability. Mechanistic studies reveal that the PIL network not only ensures high dispersion and leaching resistance of HPW clusters but also reconstructs their spatial intimacy with unsaturated Zr centers, enabling substantive Brønsted–Lewis acid synergy. This work provides a paradigm for addressing the activity–stability paradox in heterogeneous acid catalysis through rational interfacial engineering.