Engineered Fabrication of Hierarchical Frameworks with Tuned Pore Structure and N,O-Co-Doping for High-Performance Supercapacitors.

A series of multiheteroatom porous carbon frameworks (MPCFs) is prepared successfully from the trimerization of cyano groups of our designed and synthesized 4,4'-(4-oxophthalazine-1,3(4H)-diyl)dibenzonitrile monomers and subsequent ionothermal synthesis. Benefiting from the molecular engineering strategy, the obtained MPCFs framework show a homogeneous distribution of nitrogen and oxygen heteroatoms at the atomic level, confirmed by the transmission electron microscopy mapping intuitively, thereby ensuring the stability of electrical properties. The supercapacitor with the obtained MPCFs@700 as the electrode exhibits a high energy density of 65 Wh kg-1 at 0.1 A g-1, with excellent long cycle life and cycle stability (98% capacitance retention for 10 000 cycles in 1-butyl-3-methylimidazolium tetrafluoroborate). Another two electrolyte systems employed also demonstrate the delightful results, showing a 112% capacitance retention for 30 000 cycles in 1 M H2SO4 and a 95% capacitance retention for 30 000 cycles in tetraethylammonium tetrafluoroborate in an acetonitrile solution. Moreover, the successful preparation of MPCFs provides new insights into the fabrication of electrode materials intrinsically containing nitrogen and oxygen in the frameworks for readily available components through a facile routine.