Covalent Organic Framework Solid Solutions for Combined Near-Infrared Photodynamic and Drug Delivery Cancer Therapy

Covalent organic frameworks (COFs) have been emerging as versatile reticular materials due to their tunable structures and functionalities, enabled by precise molecular engineering at the atomic level. While the integration of multiple compotents into COFs has substantially expanded their structural complexity, the strategic engineering of diverse functionalities within a single framework via the random distribution of linkers with varying lengths remains largely unexplored. Here, we report a series of highly crystalline COF solid solutions synthesized using azobenzene and bipyridine as linkers, where tuning the ratio of linkers and incorporating palladium effectively modulates the balance between near-infrared (NIR) light absorption and catalytic sites for NIR-generation of hydrogen peroxide (H2O2). Capitalizing on the deep tissue penetration of NIR light and the generated H2O2 as reactive oxygen species, the optimal COF solid solution reduces breast cancer cell viability by almost 90% after 1 hour of irradiation in a combined in vitro photodynamic and drug delivery therapy.