As an emerging antibacterial strategy, photothermal disinfection attracts increasing attention due to its advantages of high efficacy, wide pertinence, and non-drug resistance. However, the unavoidable shielding of observation by photothermal components and the possible damage to normal tissue caused by hyperthermia restrict its applications. Herein, we propose a composite hydrogel with the ability of on-demand generation of photothermal components and mild-temperature photothermal disinfection by elegantly tuning the binding and release of iodine and starch. The composite hydrogel is obtained by blending iodine-adsorbed pH-responsive ZIF-8 nanoparticles (NPs) with a starch-based hydrogel matrix. Through a convenient pH response, the composite hydrogel leverages the triple functions of iodine, which serves as a disinfectant and reacts with starch to generate a photothermal agent and color indicator, allowing photothermal-chemotherapy combined disinfection on demand.