Introducing　functional　groups　into　pores　of　metal-organic　frameworks　(MOFs)　through　ligand　modification　provides　an　efficacious　approach　for　tuning　gas　adsorption　and　separation　performances　of　this　type　of　novel　porous　material.　In　this　work,　two　UiO-67　analogues,　[Zr6O4(OH)(4)(FDCA)(6)]　(BUT-10)　and　[Zr6O4(OH)(4)(DTDAO)(6)]　(BUT-11),　with　functionalized　pore　surfaces　and　high　stability　were　synthesized　from　two　functional　ligands,　9-fluorenone-2,7-dicarboxylic　acid　(H(2)FDCA)　and　dibenzo[b,d]thiophene-3,7-dicarboxylic　acid　5,5-dioxide　(H(2)DTDAO),　respectively,　and　structurally　determined　by　single-crystal　X-ray　diffraction.　Notwithstanding　skeleton　bend　of　the　two　ligands　relative　to　the　linear　4,4＇-biphenyldicarboxylic　acid　in　UiO-67,　the　two　MOFs　have　structures　similar　to　that　of　UiO-67,　with　only　lowered　symmetry　in　their　frameworks.　Attributed　to　these　additional　functional　groups　(carbonyl　and　sulfone,　respectively)　in　the　ligands,　BUT-10　and　-11　show　enhanced　CO2　adsorption　and　separation　selectivities　over　N-2　and　CH4,　in　spite　of　decreased　pore　sizes　and　surface　areas　compared　with　UiO-67.　At　298　K　and　1　atm,　the　CO2　uptake　is　22.9,　50.6,　and　53.5　cm(3)/g,　and　the　infinite　dilution　selectivities　of　CO2/CH4　are　2.7,　5.1,　and　9.0　and　those　of　CO2/N-2　are　9.4,　18.6,　and　31.5　for　UiO-67,　BUT-10,　and　BUT-11,　respectively.　The　selectivities　of　CO2/CH4　and　CO2/N-2　are　thus　enhanced　1.9　and　2.0　times　in　BUT-10　and　3.3　and　3.4　times　in　BUT-11,　respectively,　on　the　basis　of　UiO-67.　The　adsorption　mechanism　of　CO2　in　BUT-11　has　also　been　explored　through　computational　simulations.　The　results　show　that　CO2　molecules　locate　around　the　sulfone　groups　in　pore　surfaces　of　BUT-11,　verifying　at　the　molecular　level　that　sulfone　groups　significantly　increase　the　affinity　toward　CO2　molecules　of　the　framework.　This　provides　thus　an　efficient　strategy　for　the　design　of　CO2　capture　materials.