A novel coordination polymer of zinc(II) biphenyldicarboxylate bearing a sulfone group, [Zn(sbdc)(H2O)(3)]center dot(H(2)sbdc)center dot H2O (H(2)sbdc: sulfone biphenyldicarboxylic acid), has been synthesized. It is composed of a one-dimensional chain structure of alternating Zn(II) cations and sbdc anions. This coordination polymer possesses noncoordinating uncharged acid H(2)sbdc existing between the chains with hydrogen-bonding networks. The proton conductivity of [Zn(sbdc)(H2O)(3)]center dot(H(2)sbdc)center dot H2O strongly depended on the relative humidity (RH), being 2.5 x 10(-7) S cm(-1) at 95% RH. The activation energy for proton conductivity was estimated to be 0.32 eV at 95% RH.