File Name : figure s1.tif Caption : fig. s1 synthesis of br@ccof. File Name : figure s3.tif Caption : fig. s3 sem and corresponding eds elemental mapping of br@ccof. File Name : figure s2.tif Caption : fig. s2 ft-ir spectra of br@ccof, tp and eb. File Name : figure s4.tif Caption : fig. s4 sem and corresponding eds elemental mapping of so₄^2-@ccof. File Name : figure s5.tif Caption : fig. s5 eds energy spectrum of so₄^2-@ccof and h₂po₄^-@ccof. File Name : figure s6.tif Caption : fig. s6 thermogravimetric curves of prepared br@ccof and samples after ion-exchange. File Name : figure s7.tif Caption : fig. s7 nitrogen adsorption curves of comparison between br@ccof and so₄^2-@ccof. insert：pore size distribution of comparison between br@ccof and so₄^2-@ccof. File Name : figure s8.tif Caption : fig. s8 nitrogen adsorption curves comparison of br@ccof and h₂po₄^-@ccof. insert：pore size distribution of comparison between br@ccof and h₂po₄^-@ccof File Name : figure s9.tif Caption : fig. s9 ac impedance diagram of br@ccof at different relative humidity. File Name : figure s10.tif Caption : fig. s10 ac impedance diagram of br@ccof at different temperatures under rh 98% conditions. File Name : figure s11.tif Caption : fig. s11 proton conduction activation energy of br@ccof at rh 98%. File Name : figure s12.tif Caption : fig. s12 ac impedance diagram so₄^2-@ccof at different relative humidity. File Name : figure s13.tif Caption : fig. s13 ac impedance diagram of so₄^2-@ccof at different temperatures under rh 98% conditions. File Name : figure s14.tif Caption : fig. s14 proton conduction activation energy of so₄^2-@ccof at rh 98%. File Name : figure s15.tif Caption : fig. s15 comparison of water vapour adsorption curves between br@ccof and so₄^2-@ccof. File Name : figure s16.tif Caption : fig. s16 comparison of water vapor adsorption curves between br@ccof and h₂po₄^-@ccof.