The high porosity and versatile structures of metal–organic frameworks (MOFs) as new theranostic platforms have drawn broad attention and have been widely explored. This has inspired the use of MOFs to encapsulate various functional nanoparticles within the frameworks to further develop and extend the biomedical applications in drug delivery and bioimaging. Herein, we fabricated yolk–shell magnetic composites Fe₃O₄@Co/Zn-ZIF towards magnetic resonance (MR) imaging-guided chemotherapy by combining a controlled encapsulation process with a mild phase transformation under solvothermal conditions. The designed yolk–shell composites Fe₃O₄@Co/Zn-ZIF exhibited high doxorubicin (DOX) loading capacity, pH-responsive release characteristics, good biocompatibility and strong T₂-weighted MR imaging contrast enhancement. The hollow structure Co/Zn-ZIF serving as a shell could collapse under low pH conditions, and achieved controlled release of drugs. Dopamine-modified Fe₃O₄ nanoparticles (Fe₃O₄–DA NPs) as the core could confer Fe₃O₄@Co/Zn-ZIF with outstanding MR imaging capacity and facile magnetic separation. This strategy sheds light on a new way to develop multifunctional drug delivery systems by using hollow structures of MOFs as hosts for different functional nanoparticles.