Single Molecular Wells–Dawson‐Like Heterometallic Cluster for the In Situ Functionalization of Ordered Mesoporous Carbon: A T 1 ‐ and T 2 ‐Weighted Dual‐Mode Magnetic Resonance Imaging Agent and Drug Delivery System

Developing a feasible way to prepare highly dispersed heterometallic nanoparticles incorporated in porous carbon composites is of significant importance for multifunctional materials. In this work, heterometallic γ‐Fe 2 O 3 and GdPO 4 nanoparticles that are incorporated in ordered mesoporous carbon composites are facilely prepared by a one‐pot in situ method using a Wells–Dawson‐like cluster of [Fe 6 Gd 6 (μ 3 ‐O) 2 (CO 3 )(O 3 PPh) 6 (O 2 C t Bu) 18 ] ({Fe 6 Gd 6 P 6 } for short) as the precursor. It is verified that the γ‐Fe 2 O 3 and GdPO 4 nanoparticles are highly dispersed and embedded into the carbon matrix with a particle size smaller than 5 nm, even when the carbon matrix is changed from 2D hexagonal P6mm to 3D body‐centered cubic Im‐3m symmetry. Additionally, a formation mechanism is proposed. Furthermore, dual‐mode magnetic resonance (MR) imaging and drug carrier properties are evaluated by in vitro experiments, which show a satisfactory T 1 ‐ and T 2 ‐weighted MR imaging effect with r 1 and r 2 relaxivity values of 2.7 and 183.7 mM −1 s −1 , respectively, and doxorubicin hydrochloride carrier amount of 102 mg g −1 , identifying a combined function for potential diagnostic and therapy.