Two lanthanide zeolite-like metal-organic frameworks (Ln-ZMOFs) with rho topology, Tb-ZMOF and Eu-ZMOF, were constructed by self-assembly of a 4-connected lanthanide molecular building block and a bipyridine-dicarboxylate ligand. Varying the Tb3+ and Eu3+ ratio during synthesis afforded three mixed-crystal isostructural MZMOFs with variable Eu:Tb stoichiometry. Fluorescence studies revealed that a methanol suspension of one of these mixed crystals, MZMOF-3, exhibits selective detection of lysophosphatidic acid (LPA), a biomarker for ovarian cancer and other gynecologic cancers. Linear correlation between the integrated fluorescence intensity and the concentration of LPA was observed, enabling quantitative analysis of LPA in physiologically relevant ranges (1.4-43.3 mu M). MZ-MOF-3 therefore has the potential to act as a self-referencing and self-calibrating fluorescent indicator for LPA.