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[Display omitted] • The 1D open framework metal phosphate exhibits high storage, aqua and thermal stability. • It has remarkable proton conductivity of 5.14 × 10-4 S.cm−1 at 313 K and 99% RH. • Its composite membranes with PVDF exhibit a considerable proton conductivity as powder at similar condition. A 1D open framework inorganic-organic hybrid metal phosphate, compound (C 4 H 12 N 2) 1.5 [Fe 2 (OH)(H 2 PO 4)(HPO 4) 2 (PO 4)].0.5(H 2 O) was synthesized via solvothermal method. The inorganic anion layer is built from FeO 6 cluster units, and the interlayer spaces are filled by the charge-compensated piperazinium cations. The resultant compound had high storage, aqua and thermal stability by placing its samples in the air for one year, immersing in water for 7 days and performing in the temperature range of 298–1073 K with TG analysis, respectively. This compound exhibited significant temperature and humidity dependence proton conductivity, achieving 5.14 × 10-4 S.cm−1 at 313 K and 99% RH. Moreover, its composite membranes with PVDF also possessed good and sustaining proton conduction behavior (3.78 × 10-4 S.cm−1 at 323 K and 99 %RH), closing to that of its powder although the PVDF isn't electric conductive. [ABSTRACT FROM AUTHOR]

The K+ ions were doped into the inorganic layer of two 2D layer metal phosphates (C 2 H 10 N 2)[Mn 2 (PO 4) 2 ]·2H 2 O (1) and (C 2 H 10 N 2)[Mn 2 (HPO 4) 3 ](H 2 O) (2), respectively, via ion exchange method. The resultant compounds maintained the original structure of 1 and 2 , but significantly improved their proton conductivity, for example, the proton conductivity of 1 increased from 1.14 × 10−5 S.cm−1 to 3.39 × 10−2 S.cm−1 at 99% RH and 293K after doped 0.55 K+ ions; And, it's remarkably that the proton conductivity of compund 1 with 1.65 K+ ions is the highest among the disclosed open-framework metal phosphates, and has exceed some reported MOFs. • The K+ ions were doped into metal phosphates to improve their proton conductivity. • Compounds contaning K+ ions maintain original structure, but have high conductivity. • The conductivity of compund with 1.65 K+ ions is highest in metal phosphates. • The minor differences in anionic framework caused a variation in proton conductivity. Herein, the K+ ions were doped into the inorganic layer of two 2D layer metal phosphates (C 2 H 10 N 2)[Mn 2 (PO 4) 2 ].2H 2 O (1) and (C 2 H 10 N 2)[Mn 2 (HPO 4) 3 ](H 2 O) (2), respectively, via ion exchange method. The resultant compounds maintained the original structures of 1 and 2 , but significantly improved their proton conductivity, for example, the proton conductivity of 1 increased from 1.14 × 10−5 S.cm−1 to 3.39 × 10−2 S.cm−1 at 99% RH and 293 K after doped 0.55 K+ ions; the proton conductivity of 2 is 0.70 × 10−2 S.cm−1 at 99% RH and 293 K after doped 0.32 K+ ions, and is 4.3 times that of the orginal sample. Such a substantial increase in proton conductivity could be attributable to that the K+ ions in aqueous solutions create stronger electrostatic fields to accommodate water, and thus make a more dense and extensive hydrogen-bonding network to enhance the transport of protons. [ABSTRACT FROM AUTHOR]