Chemical processes and reactors for efficiently producing hydrogen fuels and structural materials and associated systems and methods. A representative process includes dissociating a hydrogen donor into dissociation products by adding energy to the hydrogen donor, wherein the energy includes waste heat generated by a process other than dissociating the hydrogen donor. The process can further include providing, from the dissociation products, a structural building block and/or a hydrogen-based fuel, with the structural building block based on carbon, nitrogen, boron, silicon, sulfur, and/or a transition metal.