Precursor‐Modulated Synthesis Enables a Stable and Activatable Mn(III) Formate With the ReO ₃ ‐Type Topology

ABSTRACT ReO ₃ ‐type metal–organic frameworks (MOFs) are a promising class of porous materials, yet their activation remains a key challenge. Aluminum formate, [Al(HCOO) ₃ ], known as ALF, is currently the only M(III)‐formate (M = Al, Fe, Mn, In, Ga) that can be readily activated, enabling applications in gas separation and storage. Here, we report a streamlined synthesis of Mn(HCOO) ₃ that yields a stable, activatable phase, overcoming the long‐standing instability of the Mn(III)‐formate. Activated Mn(HCOO) ₃ exhibits good thermal stability and excellent gas adsorption performance for CO ₂ capture, comparable to ALF itself. By successfully stabilizing a redox‐active, earth‐abundant transition metal within this architecture, our work not only broadens the accessible family of M(III)‐formate MOFs but also lays the foundation for new multifunctional applications across gas storage, separation, catalysis, and spin‐based technologies.