Herein, mesoporous 3D silicon carbide (SiC), carbonitride (Si[sbnd]C[sbnd]N) and nitride (Si3N4) structures have been synthesized by nanocasting and pyrolysis using commercial organosilicon polymers as precursors of the different compositions. Detailed characterizations by BET and XRD allowed us to fix the most appropriate parameters to design mesoporous 3D structures with high specific surface areas and high pore volume. Then, the series of 3D structures has been used as supports to grow platinum nanoparticles (Pt NPs) by wet impregnation followed by reduction in hydrogen/argon flow. The Pt-supported mesoporous 3D supports kept the mesoporosity of the virgin supports to be used for catalytic hydrolysis of sodium borohydride (NaBH4). A hydrogen generation rate of 24.2 L min−1gPt −1is measured for the Pt-supported mesoporous 3D Si3N4structure, which is notably higher than the catalytic hydrolysis using Pt-supported mesoporous 3D SiC and Si[sbnd]C[sbnd]N structures. HRTEM investigations demonstrated the homogeneous distribution of Pt NPs over the Si3N4support. © 2016 Hydrogen Energy Publications LLC