Oxygen-deficient metal-organic framework derivatives for advanced energy storage: Multiscale design, application, and future development

Owing to their dazzling physicochemical properties, metal-organic frameworks (MOFs) have been extensively studied in the arena of the energy industry. Nevertheless, the intrinsically poor conductivity hampers the electrochemical applications of pristine MOFs, which promotes the orchestrated endeavors to surmount the dissatisfying electrochemical performance by developing MOF derivatives. Simultaneously, oxygen vacancy (OV) engineering has been substantiated as an efficacious methodology to exalt the electrochemical performance from the atomic level. Herein, this review specifically focuses on oxygen-deficient MOF derivatives with exceptional electrochemical properties in energy storage. The synthetic protocols of MOF derivatives are discussed from the monomer selection to the reaction/calcination condition adjustment, endowing the diversity and controllability of MOF derivatives in compositional and structural properties. Afterward, we comprehensively evaluate OV engineering from OV classification (bulk/surface/interface oxygen vacancies), introduction (in situ thermal treatment, chemical etching, reduction reaction, etc.), and detection (Powder X-Ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, electron paramagnetic resonance, spherical aberration-corrected transmission electron microscopy, etc.). In light of the above, the applications of oxygen-deficient MOF derivatives in electrochemical energy storage and conversion (EESC) devices including lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), metal-air batteries (MABs), aqueous ion batteries (AIBs), supercapacitors (SCs), and electrocatalysts are reviewed to highlight the efficaciousness of MOF-templated and oxygen-deficient strategies for enhanced energy storage efficiency. Finally, advantages, challenges, and prospects of oxygen-deficient MOF derivatives are proposed to direct the design of energy materials for next-generation EESC devices.