Topochemical Approach for Transition-Metal Exchange Assisted by Copper Extrusion: from Cu<sub>2</sub>FeBO<sub>5</sub> to Fe<sub>3</sub>BO<sub>5</sub>

All fields of today’s technology are concerned with multifunctional materials, the subject of constantly expanding research. Among them, metal transition oxides occupy a strategic place because of the properties directly correlated with metal valence linked with oxygen stoichiometry. To enhance or induce new properties, knowledge of the relationships between the structural and physical characteristics is of prime importance, but a design at low scale also appears to be a powerful tool to increase the chemical reactivity and stabilize new compounds. Herein, an unexpected reaction is reported that associates the exchange of copper and iron in a 3D ludwigite lattice with the huge release of oxygen (14% by weight) at moderate temperature (<450 °C). Annealing of Cu<sub>2</sub>FeBO<sub>5</sub> in a reducing atmosphere leads to the extrusion of copper and the formation of Fe<sub>3</sub>BO<sub>5</sub>, the micro/nanostructural state of which facilitates the partial Cu<sub>2</sub>FeBO<sub>5</sub> recovery associated with the capture of oxygen in oxidizing conditions.