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Two proton-conductive molecular hybrid complexes, {[H(H2O)2][Sr(HINO)4(H2O)7(PW12O40)]} n (1) and {[H(H2O)2][Ca(HINO)4(H2O)5(PW12O40)]} n (2), were constructed by introducing alkaline-earth metal ions and [PW12O40]3– anions in the gallery of H-bonding networks based on isonicotinic acid N-oxide (HINO). Single-crystal X-ray diffraction analyses at 293 K reveal that both complexes crystallized in the orthorhombic space group Pnnm, and presented the same 3-D hydrogen-bonded networks with large 1-D channels. Interestingly, HINOs not only constructed 1-D hydrogen-bonded chains, but also coordinated to alkaline-earth metal ions to form decorated poly-Keggin-anions. In addition, decorated poly-Keggin-anion chains are also formed in the 1-D channels. Thermogravimetric analyses show no weight loss in the temperature range 20–70°C, indicating that all water molecules in the unit structure are not easily lost below 70°C. Surprisingly, the proton conductivities of 1 and 2 at 85–100°C under 98% relative humidity conditions reached good proton conductivities of 10−3 S cm−1. [ABSTRACT FROM PUBLISHER]