The slow kinetics of oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) pose important challenges to energy storage. Defect engineering offers an effective strategy to enhance the performance of electrocatalytic materials. In this study, we synthesized trifunctional catalysts (CoO_X/Co₉S₈@NC) derived from cobalt-based metal–organic frameworks modified with oxygen-sulfur double vacancies. These vacancies improve catalytic activity by increasing active sites and enhancing charge-transfer capacity. The CoO_X/Co₉S₈@NC catalyst demonstrates outstanding ORR and OER bifunctional activity (ΔE = 0.63 V) and HER performance comparable to noble metal catalysts. Liquid zinc-air batteries exhibited superior cycling stability (2,520 cycles at 2 mA/cm²). This defect engineering strategy presents a novel pathway for developing high-performance electrocatalysts and holds important potential for energy-conversion technologies.