## 1 Introduction  
Over the past decades, supercapacitors have become promising electronic devices for use in meeting future energy-storage requirements in industrial energy management, electric vehicles, and memory back-up systems. This is owing to the supercapacitor's unique performance, including superior power density, long life cycle, and short charging time [1; 2; 3]. Carbon-based materials with low electric resistance, such as carbon nanofibers [4; 5], activated carbon [6; 7], carbon nanotubes [8; 9], and carbon aerogel [10; 11], have been developed as electrode materials for applications in supercapacitors. Unfortunately, these materials often possess shortcomings, such as low specific surface area, uncontrolled pore size distribution, high cost, and poor mechanical properties, which limit to some degree the materials' application in supercapacitors. Recently, graphene, featuring a flat monolayer of carbon atoms arranged in a two-dimensional (2D) honeycomb lattice, exhibited intriguing physical and chemical properties, including a high charge mobility, superior thermal conductivity, a large specific surface area, and good chemical stability [12; 13; 14]. It has also been utilized widely in electrochemical sensors [15], energy storage and conversions [16; 17], and field-effect transistors [18; 19], amongst others. According to the charge-storage mechanism, all carbon-based materials possess electric double-layer capacitors (EDLC) characterization, and a low specific surface area, which leads to the material's low capacitance [20]. Therefore, the design and construction of new 2D materials with high conductivity, controllable hierarchical porous structure, and large redox activity is highly desirable for electrochemical capacitors. To date, many materials have been introduced onto graphene to achieve high performance supercapacitors. Several metal oxides and sulfides (e.g., MnO\({}_{2}\)[21; 22], NiO\({}_{\mathrm{x}}\)[23], CoO\({}_{\mathrm{x}}\)[24], MoS\({}_{2}\)[25], and Ni\({}_{3}\)S\({}_{2}\)[26]) show a fast-Faradaic reaction, leading to a higher specific capacitance for these pseudocapacitive electrode materials. Thus, the preparation of graphene-based hybrids through the loading of inorganic materials onto the surface of graphene has been confirmed as a facile strategy to obtain high performance electrode materials [27]. Using the example of Ni\({}_{3}\)S\({}_{2}\), [PERSON] et al. reported the preparation of graphene-coupled flower-like nickel sulfide monoliths using an F127-assisted hydrothermal method and high-temperature pyrolysis. The as-prepared graphene-based hybrid showed ultra-high specific capacitances of up to 1315 F g\({}^{-1}\), as well as high stability through 1000 charge/discharge cycles at 1 A g\({}^{-1}\)[26]. However, the severe aggregation tendencies of graphene and the agglomeration of inorganic nanoparticles in the hybrid structure could hinder electron and mass transport [28], resulting in low charge-discharge rates and poor gravimetric capacitances. Compared to that of heteroatom doping [29; 30], the transition metal-doping strategy could not only enhance the conductivity and electrochemical stability of the framework structures, but it could also provide several electrochemically active sites, thereby exhibiting great potential for use in energy-related applications [31]. In recent years, transition metal-doped porous carbon has been reported for use in supercapacitor applications. To the best of our knowledge, the development of 2D metal-doped porous carbon with high performance electrochemical capacitors is still a challenge [32]. Based on our previous work [33], cobalt-doped 2D graphene-coupled hypercrosslinked porous polymer nanosheets (Co-GHCP) were constructed for the present work using a nucleophilic substitution reaction of 5,10,15,20-tetra(4-pyridyl) Co (II) porphyrin and graphene-coupled poly (vinylbenzyl chloride-co-divinylbenzene), prepared via RAFT emulsion polymerization with the macromolecular chain-transfer agent of GO-DDAT.