Four novel heterometallic RE-Na-organic frameworks, [(RE)Na-3(PZTC)(2)(H2O)(4)]center dot 2H(2)O (RE = Yb (1), Ho (2), Er (3), Y (4); PZTC = pyrazine-2,3,5-tricarboxylate), were synthesized via solvothermal reactions and characterized by TB., elemental analysis, and single-crystal X-ray diffraction. The results show that the four complexes are isostructural. In the frameworks, the trinudear Na cluster and RE ion acting as nodes are bridged by the multifunctional PZTC ligand to give a 3-D framework. Codoping in the frameworks was realized due to their isostructural characteristics. The codoped complexes were calcinated at 800 degrees C to give rise to the corresponding oxides. Investigation of their photophysical properties shows that the upconversion luminescence (UCL) of the Ho system is green while that of the Er system is red upon excitation at 980 nm. With regard to the luminescence color and intensity, the Er system is preferable to the Ho system for application in bioimaging. Both the red and the green UCL of the Ho3+ and Er3+ systems involve a two-photon process. In addition, the UCL mechanism is given. The UCL comparison of Na-doped oxides with non-Nadoped oxides indicates that doping Na can greatly enhance the UCL of the Er system.