Bis(4-carbamoylpiperidinium) biphenyl-4,4′-disulfonate

In the title isonipecotamide salt 2C(6)H(13)N(2)O(+)·C(12)H(8)O(6)S(2) (2−), the asymmetric unit comprises one biphenyl-4,4′-disulfonate dianion which lies across a crystallographic inversion centre and another in a general position [dihedral angle between the two phenyl rings is 37.1 (1)°], together with three isonipecotamide cations. Two of these cations give a cyclic homomeric amide–amide dimer inter­action [graph set R (2) (2)(8)], the other giving a similar dimeric inter­action but across an inversion centre, both dimers then forming lateral cyclic R (4) (2)(8) pyrimidinium–amide N—H⋯O inter­actions. These units are linked both laterally and longitudinally to the sulfonate groups of the dianions through piperidinium N—H⋯O hydrogen bonds, giving a three-dimensional framework structure.