Hybrid inorganic/organic materials with open-framework or layered structures are known for many transition metals linked by functionalized organic molecules such as organic diphosphonates, polycarboxylates, polynitriles, etc., species with more than one equivalent functional groups. We have studied the effect of pH on such a system of cobaltmethylenediphosphonate and report three new compounds, Na3Co[(O3PCH2PO3)(OH)],Na2Co(O3PCH2PO3)•H2O, and Co2[(O3PCH2PO3)(H2O)], that form at very basic, moderately basic, and acidic conditions, respectively. More interestingstructural chemistry should be expected from linkers with two or more different functionalities. Both the carboxylic and phosphonic groups in carboxyethylphosphonic acid are used to coordinate to cobalt or calcium atoms in the new compounds Co3(O3PCH2CH2COO)2•6H2O and Ca(O3PCH2CH2COOH)•H2O. Taking one more step further in complexity we have also studied linkers with three different functional groups, phosphonated amino acids. The structures of two new compounds, Zn(O3PCH2CH(NH3)COO) and Zn(O3PCH2CH2CH(NH3)COO), are threedimensional frameworks made of zinccoordinated by both the carboxylic and phosphonic ends of the organic molecules. The amino groups are protonated and terminal in the voids of the frameworks.