Ultraefficient Ortho-Para Hydrogen Conversion by Ni-MOF-74

The interexchange between molecular hydrogen’s nuclear spin isomers, namely, ortho-hydrogen and para-hydrogen, is drastically accelerated with the metal–organic framework (MOF) of Ni-MOF-74. While the highly porous, open-metal-site-rich material reportedly shows promising ortho-para conversion efficiency (Polyukhov et al., ACS Energy Lett., 2022, 7, 4336), we unlock its power further by eliminating the alumina medium used abundantly so far, also removing impurities, and thereby optimizing the chance for the hydrogen molecules to encounter the open metal sites. With 1 H nuclear magnetic resonance, we reveal a soared ortho-para conversion efficiency upto two orders of magnitude compared to the current-best materials.