New way for the preparation of 4-sulfophenylphosphonic acid is proposed based on the hydrolysis of sulfamoylphenylphosphonic acid under hydrothermal conditions. 4-Sulfophenylphosphonic acid was successfully used for the preparation of zirconium sulfophenylphosphonate and zirconium phosphate sulfophenylphosphonate with formulae Zr(HO3SC6H4PO3)(2)center dot 2H(2)O and Zr( HPO4)(0.7)(HO3SC6H4PO3)(1.3)center dot 2H(2)O. Both compounds are layered with the interlayer distances of around 19.9 angstrom, which agrees well with the presumed structure derived from the structure of the alpha modification of zirconium phosphate monohydrate (alpha-ZrP). The inorganic part of the title compounds is identical with that of alpha-ZrP, with the sulfophenyl groups jutting out of the layers into the interlayer space. Both compounds were further characterized by FTIR and solid-state NMR, which confirmed the presence of strongly acidic hydrogen on the sulfonic group. Based on the NMR findings, the structure of hydrogen bonding in the interlayer space was proposed. The 2D H-1-H-1 spin-exchange and double-quantum NMR experiments further revealed various mutually interacting hydrogen atoms differing in their mobility. In contrast to alpha-ZrP, protons in the newly prepared systems exhibit significantly higher dynamics. The proton conductivity (sigma) of both compounds was determined at 100 degrees C as a function of relative humidity (RH) in the range 50-90% and as a function of temperature between 70 and 150 degrees C, at RH = 75%. The phosphate phosphonate compound is more conductive than the pure phosphonate compound, the highest sigma values being 0.063 S cm(-1) (at 100 degrees C and 90% RH) and 0.073 S cm(-1) (at 150 degrees C and 75% RH). Due to their insolubility in water, good thermal stability and the considerably high protonic conductivity the described layered compounds are promising candidates for application as components of composite proton exchange membranes in fuel cells. (C) 2010 Elsevier B.V. All rights reserved.