Hydrogen adsorption and storage on calcium-decorated BC2N sheets doped by Boron or Carbon were investigated using the first-principles calculations. Unlike the weak bond between Ca atoms and pristine BC2N, doping boron or carbon atoms on BC2N sheet can significantly strengthen the Ca atoms on the BC2N, especially for BC2NBC and BC2NCN. It is observed that Ca decorated BC2NBC and BC2NCN possess strong donation and back-donation of Ca with the sheets, which is responsible for enhanced binding energy to eliminate the clustering problem. Up to four hydrogen molecules can stably attach to a Ca atom with an average adsorption energy of similar to 0.3 eV, which is in the range that permits hydrogen recycling at ambient conditions. The Ca decorated BC2NBC and BC2NCN complexes can work as high-capacity hydrogen storage materials with the practical usable capacities of 8.36 wt% and 8.38 wt%, respectively. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.