The desirable air cathode in Zn−air batteries (ZABs) that can effectively balance oxygen evolution and oxygen reduction reactions not only needs to adjust the electronic structure of the catalyst but also needs a unique physical structure to cope with the complex gas−liquid environment. In this work, first-principles calculations were carried out to prove that oxygen-terminated Nb 2 CO 2 MXene played an active role in enhancing the sluggish reaction of oxygen intermediates. Nb 2 CO 2 MXene could also stimulate the spatial accumulation of discharge products, which was beneficial to improve the stability of secondary ZABs. Molecular dynamics simulation was used to show that the confinement effect of COF could effectively regulate the concentration of O 2 on the surface of Nb 2 CO 2 @COF, which was conducive to an efficient and durable reaction. COF-LZU1 was self-assembled on the interface of Nb 2 CO 2 MXene (Nb 2 CO 2 @COF) for the first time. The Nb 2 CO 2 @COF electrode had excellent OER/ORR overpotentials with the potential difference (ΔE) of 0.79 V. When applied to the configuration of ZABs, Nb 2 CO 2 @COF showed a power density of 75 mW cm −2 and favorable long-term charge/discharge stability, so it could be used as a potential candidate cathode for noble-metal-based catalysts. This idea of combining MXenes and COFs sheds some light on the design of ZABs.

A two-dimensional MXene (Ta4C3) was innovatively used herein to modulate the space group and electronic properties of vanadium oxides, and the MXene/metal–organic framework (MOF) derivative VO2(B)@Ta4C3 with 3D network cross-linking was prepared, which was then employed as a cathode to improve the performance of aqueous zinc ion batteries (ZIBs). A novel method combining HCl/LiF and hydrothermal treatments was used to etch Ta4AlC3 to obtain a large amount of accordion-like Ta4C3, and the V-MOF was then hydrothermally grown on the surface of the stripped Ta4C3 MXene. During the annealing process of V-MOF@Ta4C3, the addition of Ta4C3 MXene liberates the V-MOF from agglomerative stacking, allowing it to show additional active sites. More significantly, Ta4C3 prevents the V-MOF in the composite structure from converting into V2O5 of space group Pmmn but into VO2(B) of space group C2/m after annealing. A considerable advantage of VO2(B) for Zn2+ intercalation is provided by the negligible structural transformation during the intercalation process and the special tunnel transport channels, which have an enormous area (0.82 nm2 along the b axis). According to first-principles calculations, there is a strong interfacial interaction between VO2(B) and Ta4C3, which deliver remarkable electrochemical activity and kinetic performances for the storage of Zn2+. Therefore, the ZIBs prepared with the VO2(B)@Ta4C3 cathode material exhibit an ultra-high capacity of 437 mA h·g–1 at 0.1 A·g–1 while showing good cycle performance and dynamic performance. This study will offer a fresh approach and a reference for creating metal oxide/MXene composite structures.