The photocatalytic technique is an attractive strategy to activate persulfate for generating free radicals in the wastewater purification process. Herein, CdS nanoparticles with unique optical properties were employed to decorate the COF-based photocatalyst (denoted as TpMA) containing C₃N₄ active units via a feasible method. Interestingly, TpMA decorated with CdS nanoparticles exhibited enhanced optical absorbability and a small charge transfer resistance. Benefitting from the close interfacial connections between CdS nanoparticles and TpMA, the recombination of photogenerated electrons and holes could be effectively inhibited. As expected, the obtained CdS@TpMA composites displayed excellent photocatalytic activity, which could activate persulfate to produce SO₄⁻˙ and ˙OH under visible light irradiation. In comparison with pristine CdS nanoparticles and TpMA, the 25% CdS@TpMA composite presented the best photocatalytic degradation ability, and 97.6% of diclofenac sodium, 95.2% of tetracycline and 93.8% of ibuprofen could be effectively removed within 70 min. The corresponding TOC removal efficiencies were more than 60%. More significantly, the 25% CdS@TpMA composite displayed great performance and structural stabilities. Furthermore, a possible photocatalytic mechanism was also proposed. In short, the current work not only provides a promising candidate for degrading drug residues, but also offers some novel viewpoints for further research.