The　designability　and　tunability　of　the　pore　structure　are　the　advantage　of　metal–organic　frameworks　(MOFs)　for　adsorptive　separation　applications.　However,　it　is　still　challenging　to　design　MOF　adsorbent　rationally　according　to　industrial　demands,　because　of　the　complexity　in　the　separation　processes　and　the　relative　lack　of　structure-separation　relationship　information.　Herein,　we　established　a　contrastive　model　ingeniously　via　structural　modification　at　the　atom　level　in　three　Cu(II)-MOFs　constructed　from　isonicotinic　acid　(HINA)　and　its　fluorinated　analogue　3-fluoro-isonicotinic　acid　(HFINA),　targeting　on　controlling　pore　surface　fluorination　for　studying　light　hydrocarbon　separation.　Both　the　fluorinated　MOFs　(Cu-FINA-1　and　2)　show　notably　enhanced　C2H2/C2H4　and　C3H4/C3H6　selectivity　compared　with　Cu-INA　without　increasing　regeneration　energy　consumption.　Especially,　Cu-FINA-2　exhibits　a　considerable　IAST　selectivity　(6.3–9.3)　for　C3H4/C3H6,　while　Cu-FINA-1　achieves　a　C3H6　process　productivity　of　31.6　cm3/g　in　column　breakthrough　experiments.　Molecular　simulations　reveal　that　the　polar　F　sites　within　the　confined　pores　can　interact　with　gas　adsorbates　through　C-H···F　hydrogen　bonds,　and　the　tailored　pore　size　and　optimal　diffusion　kinetics　mainly　contribute　to　the　excellent　separation　selectivity　for　Cu-FINA-1.　This　work　highlights　how　pore　surface　fluorination　and　related　structural　evolution　can　influence　light　hydrocarbon　adsorption/separation　properties　in　MOFs,　and　thus　promotes　the　rational　design　and　precise　optimization　of　new　adsorbents　for　alkynes/alkenes　separations,　even　at　the　atom　level.　©　2020　Elsevier　B.V.