Killing Two Birds with One Stone: Unveiling Hofmann-Type MOFs on Xe/Kr and Ethylene/Ethane Adsorption Separations by Theoretical Prediction and Experimental Validation

The noble gases 129 Xe and 85 Kr mainly exist in used nuclear fuel (UNF, v/v = 20/80), while C 2 H 4 and C 2 H 6 are present in cracked gas (v/v = 50/50). The energy-efficient adsorption separations of these two important mixtures with metal–organic frameworks (MOFs) are needed but challenging. Herein, among 150 Hofmann-type MOFs, LUFRIO01 and DUMFID exhibited the top performance on Xe/Kr and C 2 H 4 /C 2 H 6 separation after grand canonical Monte Carlo (GCMC) simulations and adsorption experiment validations. These two frameworks possess fsc -net, where pyrazine (pyz) and [Ni(CN) 4 ] 2– are connected by Fe 2+ or Co 2+, respectively. For the Xe/Kr adsorption separation, LUFRIO01 and DUMFID facilitate the Xe uptakes over 2.69 mmol·g –1, with Xe/Kr IAST selectivities over 160; while for the C 2 H 4 /C 2 H 6 adsorption separation, C 2 H 4 uptakes are more than 2.58 mmol·g –1, with C 2 H 4 /C 2 H 6 selectivity over 39.10. DFT calculations reveal that the [Ni(CN) 4 ] 2– bilayer can form two C–H···Ni 2+ bonds with C 2 H 4 with the optimal distance of around 7.00 Å, representing the first report of C 2 H 4 agostic interaction with metal ions in MOFs. In summary, LUFRIO01 and DUMFID can overcome the “trade-off” issue between uptake and selectivity while “killing two birds with one stone”. Note that the present work of “theoretical prediction, experimental validation” can accelerate material development with low cost.