Metastasis is one of the main reasons for cancer treatment failure. Unfortunately, most treatment approaches inevitably damage the extracellular matrix (ECM) during tumor cell elimination, thereby augmenting the risk of metastasis. Herein, we proposed a "sieging tumor cells" strategy based on ferric coordination polymers (FeCPs), which involved anchoring tumor cells through ECM consolidation and selectively eliminating them in the tumor regions. Due to the weak coordination interactions and amorphous structure of FeCPs, the acidic tumor microenvironment facilitated their disintegration, releasing salicylic acid (SA), 2,5-dihydroxyterephthalic acid (DHTA) and Fe