Mixed-matrix　membranes　(MMMs)　incorporating　Metal-Organic　Frameworks　(MOFs)　represent　a　promising　approach　for　gas　separation,　which　can　combine　the　advantages　of　selective　adsorbents　and　processable　polymers,　and　display　great　potential　in　the　gas　separation　process.　However,　the　further　application　of　MMMs　is　severely　impeded　owing　to　the　non-ideal　interface　between　fillers　and　polymer　matrix.　In　this　work,　a　series　of　MIL-101(Cr)　nanofillers,　equipped　with　different　kinds　of　counter　anions　were　introduced　to　regulate　the　chemical　microenvironment　of　the　MMMs　and　improve　the　interfacial　relationship　between　inorganic　filler　and　polymer.　The　filler　of　MIL-101-HNO3　exhibits　improved　dispersibility　in　solvents　and　heightened　interface　relationship　with　the　polymer　matrix　(PIM-1)　due　to　its　optimal　particle　size　and　distinctive　exposure　of　crystallographic　planes.　Moreover,　gas　sorption　isotherms　reveal　that　the　MIL-101-HNO3　MOF　show　reduced　N2　adsorption　capacity.　Therefore,　the　MOF　filler　of　MMMs　were　optimized　rationally　by　microenvironment　regulate　strategy,　leading　to　the　MIL-101-HNO3/PIM-1　MMMs　achieve　high　CO2　permeability　and　exceptional　CO2/N2　ideal　selectivity　(CO2　=　14879　barrer,　CO2/N2　=　24.3),　surpassing　the　latest　2019　upper　bound.　That　makes　MIL-101-HNO3/PIM-1　a　potential　candidate　for　the　selective　removal　of　CO2　from　stack　gas　and　provides　new　insights　into　the　regulation　of　the　MMMs　nanofiller　microenvironment.　©　2024　Elsevier　B.V.