Nanostructured Polybenzoxazine Particle-Supported Ammonia Borane for Hydrogen Storage and Release

The development of advanced solid-state hydrogen storage necessitates the design of catalytic nanostructures with interactive interfaces capable of modulating the hydride decomposition pathways for controlled hydrogen release. In this work, two functionalized polybenzoxazine (PBz) nanostructures bearing hydroxyl and nitrile groups were synthesized via a colloidal sol–gel method using aniline and 4-aminobenzonitrile, respectively, and employed as active scaffolds for ammonia borane (AB) thermolytic dehydrogenation. To optimize structural accessibility and confinement, 1,3,5-trimethylbenzene was used as a dynamic porogen to induce macroporosity, while mesoporous silica served as a hard template to introduce mesoporosity within the PBz matrix. Compared to neat AB, the aniline and 4-aminobenzonitrile-derived PBz-supported AB systems demonstrated substantially reduced onset dehydrogenation temperatures and significantly lower activation energies of 68.4 kJ mol –1 and 91.13 kJ mol –1, respectively, reflecting enhanced kinetic behavior. Spectroscopic and structural analyses revealed the strong interaction of AB with surface functionalities via B–O and B–N bond formation, disrupting its characteristic dative and dihydrogen bonding. The utilization of structural modifiers in both PBz matrices also resulted in microenvironments conducive to enhanced interfacial contact with AB, leading to significant size reduction in the confined AB crystallite and resulting in reduced peak dehydrogenation temperature. Furthermore, the PBz nanostructures demonstrated excellent regeneration and reusability over multiple cycles, maintaining their structural integrity and hydrogen release capacity for up to three cycles. This work demonstrates the interplay between morphology-driven confinement and interfacial chemistry in tailoring the performance of polymer–hydride hybrid nanomaterials, offering a promising strategy for developing functionalized nanomaterials for hydrogen storage.