Two metal-organic frameworks (MOFs), MOF-501 and MOF-502, respectively, formulated as Co-2(BPTC)(H2O)(5)(.)G(x), and Co-2(BPTC)-(H2O)(DMF)(2)(.)G(x) (BPTC = 3,3',5,5'-biphenyltetracarboxylate; G = guest molecules), have been synthesized and structurally characterized, and their topologies were found to be based on the NbO (MOF-501) and PtS (MOF-502) nets. Heating MOF-501 in solution results in the more thermodynamically favored MOF-502.