Sequential reaction of a lower-rim functionalized calix[4]arene, 25,27-bis(hydroxycarbonylmethoxy)-26,28-dimethoxy-p-tert-butylcalix[4]ar ene (H2LC4), with K2CO3 and CoCl2 center dot 6H(2)O in ethanol afforded a 3D coordination polymer [K3Co2(L-C4)(3)(EtOH)(6)]Cl (1). X-ray crystal analysis revealed that 1 features a noninterpenetrated (10,3)center dot a net structure wherein octahedral Co2+ ions serve as the three-connecting nodes and [K(L-C4)](-) units function as the bridges between the Co2+ ions. The calixarene ligands in 1 adopt a 1,3-alternate conformation, and there are considerable cation-pi interactions between the K+ ion and the phenyl rings within each [K(L-C4)](-) unit.