A　new　microporous　organic　polymer　(PCB–NH2)　has　been　synthesized　based　on　amine　functionalized　carbazole　derivative　by　oxidative　coupling　polymerization　with　anhydrous　FeCl3.　Polymer　PCB-NH2　exhibits　microporous　nature　with　a　BET　surface　area　of　542.4　m2　g−1,　and　shows　moderately　high　CO2　and　C2H2　adsorption　capacities,　51.6　cm3　g−1　(10.3　wt%),　58.4　cm3　g−1　(7.5　wt%)　at　278　K,　1　atm,　respectively.　Remarkably,　at　278　K,　the　predicted　IAST　selectivities　of　PCB-NH2　are　16.7–5.8　for　a　CO2/CH4　(5:95　v/v)　gas　mixture　and　34.3–21.0　for　a　C2H2/CH4　(50:50　v/v)　gas　mixture　at　pressures　varying　from　0　to　1　atm,　respectively.　More　interesting,　PCB-NH2　displays　higher　CO2/CH4　selectivity　than　its　matrix　polymer　PCB.　The　isosteric　heats　of　CO2　adsorption　(Qst)　for　PCB-NH2　and　PCB　further　indicate　that　the　amine　group　may　facilitate　the　interaction　between　the　polarizable　CO2　molecules　and　the　polymer　by　local　dipole−quadrupole　interactions,　subsequently　favors　selective　gas　separation　for　these　gas　molecules.　The　high　selectivity　of　CO2/CH4　and　C2H2/CH4　makes　PCB-NH2　possible　candidate　for　future　natural　gas　upgrading　and　acetylene　purification.　©　2018　Elsevier　Inc.