Utilizing MOF precursors toward one-step, calcination-free synthesis of MnO2 superstructures for superior lithium storage

Abstract

Rationally controlled synthesis of transition metal oxide materials for structure-related applications in diverse areas at room temperature and ambient atmosphere remains a challenge. In this article, we propose a facile one-step calcination-free approach for the rational and green synthesis of 3D hierarchical polyhedron-shaped superstructures of manganese dioxide (MnO₂) through the simultaneous ion exchange and oxidation of a preformed Mn-based M₂(dobdc) (dobdc = 2,5-dihydroxy-1,4-benzenedicarboxylate) MOF (CPO-27-Mn) template with an adequate open aqueous alkaline solution of a moderate concentration at room temperature, as well as their application in rechargeable lithium cells. Concretely, we proposed that during the solution-phase process, upon exchange of the anionic dobdc⁴⁻ ligand with OH⁻, the resultant intermediate manganese hydroxide reacts with dissolved O₂ in solution to form MnO₂. Electrochemical evaluation showed that the as-synthesized hierarchical MnO₂ superstructures exhibited excellent electrochemical performance, including high reversible specific reversibility (866.4 mA h g⁻¹), superior rate capability and long-term cycling stability (797.9 mA h g⁻¹ after 300 cycles at 1000 mA g⁻¹) when serving as anodes. This unique novel MOF-derived protocol provides an alternative perspective on the designed fabrication of advanced transition metal oxide functional nanomaterials.