The high surface area and interconnected network porosity of metal-organic frameworks (MOFs) provides great potentials for gas storage and separation. For example selective adsorption and separation of radioactive Xenon and Krypton from spent nuclear fuels is of particular interest in the nuclear reprocessing applications. In this work, we employed the dispersion-corrected density function theory method to investigate the adsorption site and binding energetics of rare gases (Xe, Kr) in different M-DOBDC (M = 4d metals; DOBDC = 2,5-dihydroxyterephthalic acid) MOFs. In particular, we elaborate our calculation on Ni-DOBDC, a MOF material with high adsorption capacity for Xe and high Xe/Kr selectivity [1,2]. With the proper inclusion of the long-range van der Waals (vdW) dispersion interactions and the on-site Hubbard U correction to the transition metal d orbitals, our calculations have reproduced the measured structural properties (e.g. lattice parameters, nearest Ni-Ni, Ni-gas and gas-gas distances) within 1-2% from X-ray diffraction measurements and supported the formation of a nearly planar hexagon by the adsorbed rare gas atoms adjacent to the open metal sites [2]. The adsorption energy was dominated by dispersion interactions with the leading contribution from the open metal site. In addition, a secondary adsorption site, as observed from X-ray measurement at the center of MOF channel, was confirmed based on the total energy gain from attractive dispersion interaction with adsorbed atoms at the primary sites. Our comparative studies of Xe and Kr adsorption provide valuable insight of the observed Xe/Kr selectivity and difference in adsorption capacity and strength [1,2]. [1] Liu, J.; Thallapally, P. K.; Strachan, D., Langmuir 2012, 28 (31), 11584-11589. [2] Ghose, S. K.; Li, Y.; Yakovenko , A.; Dooryhee, E.; Ehm , L.; Ecker, L.; Greg, H.; Strachan, D. M.; Thallapally, P. K., submitted.

Adsorption characteristics of rare gases (Xe, Kr) in metal-DOBDC from first-principles calculation

249th National Meeting (2015)

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