Catalytic oxidation is frequently employed to remove hydrogen isotopes to diminish the risk from tritium leakage and hydrogen explosion. However, Pt particle aggregation and deactivation from water are the major challenges for traditional catalysts. Herein, we design hydrophobic anchoring sites to bind Pt nanoparticles through constructing covalent triazine frameworks on cordierite for the efficient oxidation of hydrogen isotopes. The Pt nanoparticles were uniformly dispersed with a diameter of 1.8–2.4 nm on the catalyst. The catalyst has a high catalytic activity for H2/D2 oxidation at 25–65 °C and high space velocity (≤30,000 h–1). It retains stable catalytic activity in 246 h continuous and intermittent operations and exhibits a lower isotope effect (KF,H/KF,D = 1:0.7) than most of the reported Pt catalysts, indicating good catalytic activity for tritium oxidation. This work provides a Pt-anchoring nanocatalyst with high hydrophobicity for the oxidation of hydrogen isotopes, which can be an effective strategy for designing catalysts.