Abstract The separation of ethylene (C 2 H 4 ) and acetylene (C 2 H 2 ) is challenging due to their similar molecular dimensions and boiling points, making conventional methods like cryogenic distillation and solvent extraction inefficient and environmentally harmful. Fluorinated metal‐organic frameworks (MOFs) have been proven to be an effective material for the separation of C 2 H 4 and C 2 H 2. However, their direct synthesis is relatively expensive and challenging. In this study, we report a facile post‐synthetic modification strategy to introduce fluorinated alkane pores into a zirconium‐based MOF, MOF‐808. The construction of fluorine‐containing pores within the MOFs prefers adsorption for C 2 H 2 attributed to the interaction between the fluorine atoms and C 2 H 2 . This series of fluorinated MOFs demonstrates potential for gas separation processes, with the highest separation ratio reaching 2.67 (1 : 99) at 298 K. Breakthrough experiments for C 2 H 2 /C 2 H 4 mixtures confirmed that fluorinated MOF is capable of separating C 2 H 2 /C 2 H 4 , making it a potential candidate for industrial application. Moreover, the simplicity of the post‐synthetic modification method suggests a viable strategy for the synthesis of fluorinated MOFs.