Heterostructure engineering was applied for the first time in two-dimensional conductive metal–organic frameworks (2D c-MOFs) to enhance their electrochemical performance, which is of great significance for the exploration of promising electrode materials for high-performance supercapacitors. Specifically, a novel 2D c-MOF-based heterostructure (copper catecholate (Cu-CAT)@Cu₂O) was in situ constructed through gamma-ray radiation-induced one-pot way under ambient conditions. The existence of Cu₂O in Cu-CAT was confirmed by diverse spectroscopic techniques and high-resolution electron microscopy images. Additionally, the constructed heterostructure significantly improved electrochemical performance, as demonstrated by experimental and theoretical analyses. Notably, Cu-CAT@Cu₂O exhibited an impressive gravimetric capacitance of 761 F·g⁻¹, nearly 3 times that of solvothermally synthesized Cu-CAT (262 F·g⁻¹), along with superior rate capability, faster charge–discharge kinetics, and excellent cycling stability. Furthermore, a symmetric two-electrode flexible supercapacitor device fabricated with Cu-CAT@Cu₂O achieved a high specific capacitance of 417 F·g⁻¹, a remarkable energy density of 98.5 Wh·kg⁻¹, and a better retention of 94.5% of its initial capacitance after 10,000 cycles. These findings highlight the potential of radiation-assisted heterostructure engineering as a versatile strategy for developing advanced MOF-based supercapacitors.

Introduction of active centers, such as oxygen vacancy and metal single atoms, has emerged as a promising strategy to further improve the electrochemical properties of transition metal oxide electrodes for high-performance pseudocapacitors. Here, an unprecedented MoO₃ with multiple active centers, Ni anchored reduced MoO₃ with oxygen vacancy (Ni-rMoO_3−x), was in situ synthesized via γ-ray radiation-induced one-pot strategy under ambient conditions. This approach leverages the synergistic effects of radiation activation, etching, and reduction. The characteristics of multiple valence states (Mo^4+/5+/6+ and Ni^0/2+), oxygen vacancies, single atoms, and atomic clusters in Ni-rMoO_3−x were determined by X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure spectroscopy (XAFS), and atomic-resolution aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) measurements. Notably, Ni-rMoO_3−x exhibited exceptional pseudocapacitive performance, with ultrahigh specific charge (881.0 C·g⁻¹ at 1 A·g⁻¹, more than twice that of MoO₃), fast charge/discharge rates, and remarkable cycle life stability (98.5% capacitance retention after 10,000 cycles). Furthermore, a hybrid supercapacitor device (Ni-rMoO_3−x//activated carbon (AC)) demonstrated a high energy density of 97.8 Wh·kg⁻¹ at a power density of 0.90 kW·kg⁻¹ and exhibited excellent mechanical flexibility for practical applications.