Low-cost melamine and 4-formylphenylboronic acid were assembled into new covalent melamine-boroxine frameworks (COFs) with rich content of nitrogen and boron by a simple one-pot synthesis routine. B,N-codoped carbons (B-N-C) could be successfully derived by copper-assisted thermal conversion of this designed plate-like COF. Differ from other microporous carbon plates derived from COFs, the prepared B-N-C here not only showed the unique hollow capsule morphologies, but also demonstrated the dominant mesoporosities. The easy-decomposition melamine-boroxine organic blocks and catalysis and template functions of Cu species including Cu(NO3)(2), Cu-2(NO3)(OH)(3) and Cu played the vital roles in the formation of hollow B-N-C capsules. The B-N-C capsules exhibited efficient catalytic performance for oxygen reduction reaction (ORR) in wide pH electrolytes, especially in alkaline solution. Its ORR half-wave potential reached 0.85 V in 0.1 M KOH, 20 mV more positive than the best B, N-codoped carbons previously. It also served as an advanced electrode material for supercapacitor with a specific capacitance of 230 F g(-1). This research not only developed a novel copper-assisted thermal conversion pathway of melamine-boroxine frameworks for preparing heteroatom-doped carbons with open capsule morphology and large-pore mesoporosities, but also provided a reliable metal-free ORR electro-catalyst and capacitor material with satisfying performance. (C) 2018 Elsevier Ltd. All rights reserved.