Defying Thermodynamics: Stabilization of Alane Within Covalent Triazine Frameworks for Reversible Hydrogen Storage

The highly unfavorable thermodynamics of direct aluminum hydrogenation can be overcome by stabilizing alane within a nanoporous bipyridine-functionalized covalent triazine framework (AlH3@CTF-bipyridine). This material and the counterpart AlH3@CTF-biphenyl rapidly desorb H2 between 95 154 °C, with desorption complete at 250 °C. Sieverts measurements, 27Al MAS NMR 27Al{1H} REDOR experiments, computational spectroscopy reveal that AlH3@CTF-bipyridine dehydrogenation is reversible 60 °C under 700 bar hydrogen, >10 times lower pressure than required to hydrogenate bulk aluminum. DFT calculations EPR measurements support an unconventional mechanism whereby strong AlH3 binding bipyridine results in single-electron transfer form AlH2(AlH3)n clusters. resulting size-dependent charge redistribution alters dehydrogenation/rehydrogenation thermochemistry, suggesting novel strategy enable reversibility high-capacity metal hydrides.