The carbon content of mesostructured organic-inorganic hybrid material of a cylindrical block copolymer template of poly(2-vinylpyridine)-block-poly(allyl methacrylate) (P2VP-b-PAMA) and ammonium paramolybdate (APM) could be reduced by thermal depolymerization. By calcination in vacuo at 320 °C the PAMA core can be completely removed while the remaining P2VP brush preserves the mesostructure. The P2VP-APM composite can then be carburized in-situ to MoOxCy in a second pyrolysis step without any additional carbon source but P2VP. The molybdenum oxycarbide nanotubes obtained, form hierarchically porous non-woven structures, which were tested as catalyst in the decomposition of NH3. They proved to be catalytically active at temperatures above 450 °C. The activation energy was estimated from an Arrhenius Plot to be 127 kJ·mol–1.