Construction of Battery-Like Hierarchical MOF@MXene\nHeterostructures for Hybrid Supercapacitors

Presently,\ntwo-dimensional (2D) hybrid metal–organic framework\n(MOF) heterostructures have drawn much attention in energy-storage\nareas. Rapid transport and full diffusion of ions could favor the\nfull utilization of active sites, giving 2D MOF heterostructures a\nrobust electrochemical performance. Herein, to optimize ion transport\npaths and promote ion penetration ability, a block copolymer was used\nto produce mesopores inside 2D MOF nanosheets, constructing a hierarchically\nporous MOFs@MXene hybrid. The energy-storage mechanism analysis shows\nthat diffusion-controlled behaviors play a dominant role over surface\ncapacitive behaviors in storing charges of the hierarchical hybrids.\nThe resulting Meso-Cu-Zn-MOFs@Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> delivers a capacity of 61.8 mA h g<sup>–1</sup> (404 F g<sup>–1</sup>) at 0.2 A g<sup>–1</sup> and\na good rate capacity (53 and 44.4 mA h g<sup>–1</sup> at 1\nand 5 A g<sup>–1</sup>, respectively). Furthermore, an assembled\nMeso-Cu-Zn-MOF@Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub>//AC hybrid device exhibits an energy density of 35.6 W h kg<sup>–1</sup> at a power density of 425.8 W kg<sup>–1</sup> (0.5 A g<sup>–1</sup>) and a power density of 4.25 kW kg<sup>–1</sup> at an energy density of 27.1 W h kg<sup>–1</sup> (5 A g<sup>–1</sup>).