A new pillared-layer coordination polymer, [Co-3(pybz)(2)(pico)(2)](n) (1; pybz = 4-(pyridin-4-yl)benzoate, pico = 3-hydroxypicolinate), contains rare 2D [Co-3(pico)(2)](n)(2n+) layers formed by linear cobalt(II) trimers through the unusual mu(4)-kappa N, O:kappa O'-mu(2):kappa O ''-mu(2) bridging mode of pico ligands, which are further cross-pillared by exotridentate bridging pybz ligands to form a three-dimensional structure with an unusual uninodal 8-connected body-centered-cubic topology. The bulk magnetic behavior of 1 exhibits ferrimagnetic long-range ordering below 2.6 K, which mainly arises from the cooperative magnetic effect of the intra- and intertrimer arrangements in the 2D magnetic system based on the nature of the exchange modes of mu(2)-hydroxyl, mu(2)-carboxylate oxygen, and 1,1,3-mu(3)-carboxylate bridges.