Inorganic-organic crystalline synthetic bilayers consisting of polyoxomolybdate and double-chained surfactants

[Display omitted] •Inorganic-organic hybrid synthetic bilayers were successfully crystallized.•Octamolybdate anion and double-chained surfactant cations were utilized.•The hybrid crystals were homologues with distinct layered structures.•Sodium ions were comprised in the layered structures of the homologues. Synthetic bilayers of double-chained surfactants were successfully constructed by using polyoxomolybdates as inorganic–organic hybrid crystals. Dialkyldimethylammonium ([(CnH2n+1)2N(CH3)2]+, (Cn)2; n = 10, 12, 14, 16) cations were employed to hybridize with octamoybdate ([Mo8O26]4–, Mo8) anion. The obtained crystals were homologues which possessed distinct layered structures composed from alternate stacking of Mo8 monolayers and (Cn)2 bilayers. The layered distances were controllable with an increase in the alkyl chain length of the (Cn)2 cation. Each alkyl chain of (Cn)2 was interdigitated to result in rather unique conformations for the (Cn)2 cations packed in the solid states. Inside the inorganic monolayers, the Mo8 anions were associated with sodium ions to form two-dimensional network, which could be promising for sodium-ion conductive materials.