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

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.