<p>In this study, a general approach to prepare metal-organic framework (MOF)-based heterogeneous catalysts is proposed. The Ce⁴⁺-modified MOFs were obtained by the co-precipitation of catalytic active Ce⁴⁺ ions and catalytic inactive MOFs (ZIF-67, MOF-5, and ZIF-8). The Ce⁴⁺-modified MOFs retained the phosphatase-like activity of Ce⁴⁺ ions and were used for the fluorescent detection of phosphorylated amino acids by using <i>o</i>-phospho-L-tyrosine (p-Tyr) as a model target. Using Ce⁴⁺-modified ZIF-67 particles as the heterogeneous catalysts, the linear range for p-Tyr detection is 1–10 µM with a detection limit of 0.26 µM. Compared with homogeneous Ce⁴⁺ ion catalysts, a significant improvement in the sensitivity was achieved by using Ce⁴⁺-modified ZIF-67 particles as heterogeneous catalysts (from 11.21 to 0.26 µM). As the proposed method holds great promise in the fluorescent detection of phosphorylated amino acids, the Ce⁴⁺-modified ZIF-67-based catalytic system was further used for the discrimination of normal peptides and phosphorylated peptides with excellent resolution.</p> Graphical Abstract <p></p>