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Metal carbonyl complexes can readily liberate carbon monoxide (CO) in response to activation stimulus. However, applicability of metal carbonyl complexes is limited because they are unstable under natural ambient conditions of moisture and oxygen. Reported here is the rational design of an iron carbonyl complex delivery nanosystem for the improvement of cancer therapy. We demonstrated that iron pentacarbonyl (Fe(CO)5) can be encapsulated into the cavity of a Au nanocage under an oxygen-free atmosphere and then controllably form iron oxide on the surface of the Au nanocage under aerobic conditions. The formation of iron oxide efficiently avoids the leakage and oxidation of the caged Fe(CO)5. The resulting nanomaterial exhibits excellent safety, biocompatibility, and stability, which can be specifically activated under near-infrared (NIR) irradiation within the tumor environment to generate CO and iron. The released CO causes damage to mitochondria and subsequent initiation of autophagy. More importantly, during autophagy, the nanomaterial that contains iron and iron oxide can accumulate into the autolysosome and result in its destruction. The produced CO and iron show excellent synergistic effects in cancer cells.

We report on the benzoporphyrin-based metal–organic framework (TBP-MOF), with 10-connected Zr6 cluster and much improved photophysical properties over the traditional porphyrin-based MOFs. It was found that TBP-MOF exhibited red-shifted absorption bands and strong near-infrared luminescence for bioimaging, whereas the π-extended benzoporphyrin-based linkers of TBP-MOF facilitated 1O2 generation to enhance O2-dependent photodynamic therapy (PDT). It was demonstrated that poly(ethylene glycol)-modified nanoscale TBP-MOF (TBP-nMOF) can be used as an effective PDT agent under hypoxic tumor microenvironment. We also elucidated that the low O2-dependent PDT of TBP-nMOF in combination with αPD-1 checkpoint blockade therapy can not only suppress the growth of primary tumor, but also stimulate an antitumor immune response for inhibiting metastatic tumor growth. We believe this TBP-nMOF has great potential to serve as an efficient photosensitizer for PDT and cancer immunotherapy.