Synergistic Defect and Halide Catalysis for CO ₂ Cycloaddition on ZIF‐8: Mechanistic and Energetic Insights from Density Functional Theory

Understanding the mechanism of CO 2 cycloaddition with epoxides under mild conditions is vital for advancing green carbon capture and utilization strategies. This work investigates the catalytic role of a defective ZIF‐8 model with Zn–OH–Zn moieties and bromide (Br − ) assistance in promoting the conversion of CO 2 and propylene oxide into propylene carbonate. Density‐functional theory calculations reveal that, in the absence of a catalyst, the reaction proceeds through high activation barriers (52.02 kcal mol −1 and 59.31 kcal mol −1 for the α and β pathways, respectively). Upon introducing the Zn–OH–Zn site and Br − , the energy barrier for the rate‐limiting ring‐opening step is drastically lowered to 14.45 kcal mol −1 , confirming the synergistic effect between Lewis acid/base sites and halide assistance. The calculated reaction energy of −13.89 kcal mol −1 aligns well with the experimental enthalpy change (−12.64 kcal mol −1 ). This study provides molecular‐level insights into the cooperative catalytic mechanism and supports defect‐engineering strategies for metal–organic frameworks in CO 2 fixation applications.