## 1 Introduction  
Nowadays, the growing energy crisis has enormously accelerated the demand for efficient, safe and cost-effective energy storage devices [1; 2]. Because of unparalleled advantages such as superior power density, strong temperature adaptation, a fast charge/discharge rate and an ultralong service life, supercapacitors have significantly covered the shortage of conventional physical capacitors and batteries, and sparked considerable interest in the last decade [3; 4; 5]. Supercapacitors are generally classified into electric double layer capacitors storing energy depending on reversible ions absorption at the interface [6; 7; 8; 9] and pseudocapacitors through reversible faradaic redox reactions [10; 11; 12; 13]. The different energy storage mechanisms directly determine whether electric double layer capacitors utilize carbonaceous materials as electrode materials [6; 7; 14], while pseudocapacitors employ transition metal oxides/hydroxides [10; 11; 15]. Drawing a benefit from faradaic redox reactions, pseudocapacitors usually generate several times higher specific capacitance than that of electric double layer capacitors, and have attracted major attention in recent years [15; 16]. Among various transition compounds, Co\({}_{3}\)O\({}_{4}\) is extensively recognized as one of the most representative pseudocapacitive materials owing to its abundant resources, environmental friendliness, low cost, strong redox activity and more importantly its superior theoretical specific capacitance (3560 F/g) [17; 18; 19; 20]. The series of excellent features have triggered tremendous efforts on Co\({}_{3}\)O\({}_{4}\) research for high performance supercapacitors application. To date, various solid or hollow structures of Co\({}_{3}\)O\({}_{4}\) have been achieved. The previous progress illustrated the hollow architecture that a highly porous morphology could provide for a large electroactive surface area with extra active sites and facile ions transportation, consequently enhancing the electrochemical properties dramatically [21; 22]. For instance, [PERSON] et al. reported hollow Co\({}_{3}\)O\({}_{4}\) cages and presented the specific capacitance of 948.9 F/g at 1 A/g (536.8 F/g at 40 A/g) [23]. The hollow Co\({}_{3}\)O\({}_{4}\) nanotubes prepared by [PERSON] et al. demonstrated the specific capacitance of 1006 F/g at 1 A/g (512 F/g at 10 A/g) [24]. [PERSON] et al. synthesized hollow Co\({}_{3}\)O\({}_{4}\) spheres and hollow Co\({}_{3}\)O\({}_{4}\) microflowers. The spheres deliver the specific capacitance of 342.1 F/g at 0.5 A/g (235 F/g at 10 A/g), while the microflowers show the specific capacitance of 210 F/g at 0.5 A/g (180 F/g at 10 A/g) [25]. However, the obtained specific capacitances up to now are far lower than their maximum theoretical value. Moreover, the Co\({}_{3}\)O\({}_{4}\) also suffers from a poor rate performance. Obviously, both low specific capacitance and poor rate performance severely hinder the practical application of Co\({}_{3}\)O\({}_{4}\). Therefore, even though major contributions are achieved, there is still much room to deeply investigate the ability of the hollow Co\({}_{3}\)O\({}_{4}\) to reach a large specific capacitance closer to its maximum theoretical value, as well as an excellent rate capability. Recently, metal-organic frameworks (MOFs), in which zeolitic imidazolate framework (ZIF) is most representative, have received much attention for constructing a hollow nanostructure for supercapacitor applications. By using the ZIF as a self-sacrificial template, a well-defined hollow structure as well as a highly electrolyte ions accessible surface area can be achieved [26; 27; 28]. Unfortunately, it is difficult to control the sizes of nanoarchitectures via a facile approach at present, which fails to further enhance the electrochemical performance. In this paper, hollow Co\({}_{3}\)O\({}_{4}\) nanoboxes were successfully prepared from ZIF-67 precursors.