3D boron dipyrromethene (BODIPY)-Fe(iii) coordination polymer nanoparticles can extend absorption to 1300 nm for enhanced ligand-to-metal transfer. The nanoparticles show good cytotoxic hydroxyl radical (˙OH) generation ability, high photothermal conversion, and outstanding NIR-II photoacoustic imaging, displaying synergistic chemodynamic/photothermal therapy.