Carboxymethyl Cellulose-Induced Phase Transformation of Metal-Organic Framework-Derived Vanadium Oxides for High-Rate...

Conventional synthesis of metal oxides from metal-organic frameworks (MOFs) precursors typically relies on high-temperature pyrolysis, which inherits the structural advantages of MOFs but is energy-intensive. Herein, we report a low-energy hydrothermal transformation strategy to fabricate two phase-pure vanadium oxides (VO₂ and V₃O₇·H₂O) without high temperature treatment. The tunnel-structured VO₂ nanobelts with high oxygen vacancy defects can be obtained by the function of water-soluble polymer sodium carboxymethyl cellulose (CMC), which plays a critical phase-directing role by coordinating with released vanadium ions on the V-MOF surface. As a cathode for aqueous zinc-ion batteries (AZIBs), the VO₂ nanobelts deliver high specific capacities of 320.8 mAh g^-1 at 0.1 g^-1 and 242.2 mAh g^-1 at 10 A g^-1, significantly outperforming the CMC-free V₃O₇·H₂O counterpart (309.5 and 162.3 mAh g^-1). Moreover, VO₂ exhibits a high-capacity retention of 73.6% after 1400 cycles at 10 A g^-1. The enhanced electrochemical behavior arises from the synergistic effects of the tunnel structure, uniform nanobelt morphology, and abundant oxygen vacancies, which facilitate Zn²⁺ diffusion and electronic conduction. This work not only provides a high-performance VO₂ cathode for AZIBs but also establishes a general, low-cost, and scalable hydrothermal route for phase-engineered MOF-derived metal oxides.