Hierarchical Porous Carbon Derived from Covalent Triazine Frameworks for High Mass Loading Supercapacitors

Here, we report a straightforward approach to synthesize hierarchical porous carbons (HPCs) via a high-temperature ionothermal synthesis and partial pyrolysis of covalent triazine frameworks (CTFs) in molten ZnCl2. By using 1,4-dicyanobenzene (DCB), 1,3-dicyanobeznene (mDCB), or 2,6-dicyanopyridine (DCP) as the monomer precursors for the CTFs, we found that ZnCl2 acts as an effective porogen in the system from monomers with weak solvent–solute interactions (DCB and mDCB). The resulting HPCs derived from DCB and mDCB exhibit a systematically tunable hierarchical porosity with an average pore size ranging from 2.5–8.0 nm, by varying the concentration of monomers in solution. We show a decreasing DCB to ZnCl2 ratio gives rise to larger mesopores, with improved pore connectivity and accessibility that is beneficial to mass transport and ion diffusion for high performance electric double layer capacitors (EDLCs) at high mass loadings. We demonstrate EDLCs with specific capacity values over 155 F/g at high mass loadings of 15 mg/cm2, delivering exceptional areal capacities of over 2.27 F/cm2 at low rates and 1.48 F/cm2 at high rates.