The first-principles calculations demonstrate that nitrogen-containing carbon nanostructures (NCCN), such as nitrogen-doped graphene, nitrogen-doped carbon nanotubes, and covalent triazine-based framework (CTF) are promising metal-free catalysts for the first step dehydrogenation of ammonia borane (AB). It reveals that nitrogen lone pairs in NCCN function as hydrogen acceptors to allow metal-free hydrogen transfer from AB to NCCN, resulting in facile release of pure H2 from AB. The dehydrogenation of AB–NCCN combined systems involves two key steps: First, there is a net transfer of hydrogen atoms from AB to NCCN that results in simultaneous dehydrogenation of AB and hydrogenation of the NCCN, and then, the hydrogenated NCCN further react with AB to release H2 with relatively low reaction barriers. The experimental results further confirm that the CTF can act as effective catalysts for AB dehydrogenation at relatively low temperature. Our study leads to a promising scheme that can be readily tailored for application to many nitrogen-containing nanostructure systems that may favorably catalyze the dehydrogenation of ammonia borane and other related boron–nitrogen species.