author ="Pham, Tony and Forrest, Katherine A. and Space, Brian",
title  ="An unusual H2 sorption mechanism in PCN-14: insights from molecular simulation",
journal  ="Phys. Chem. Chem. Phys.",
year  ="2016",
volume  ="18",
issue  ="31",
pages  ="21421-21430",
publisher  ="The Royal Society of Chemistry",
doi  ="10.1039/C6CP02650H",
url  ="http://dx.doi.org/10.1039/C6CP02650H",
abstract  ="Simulations of H2 sorption were performed in PCN-14{,} a metal-organic framework (MOF) that consists of Cu2+ ions coordinated to 5{,}5[prime or minute]-(9{,}10-anthracenediyl)diisophthalate (adip) linkers. This MOF displays an excess H2 uptake of 2.70 wt% at 77 K and 1.0 atm and an initial H2Qst value of 8.6 kJ mol-1 according to previous experimental measurements. The experimental H2 sorption isotherms and Qst values in PCN-14 were reproduced in simulations using well-known H2 potentials that have been widely used for MOF-H2 theoretical studies. H2 sorption in PCN-14 was dominated by repulsion/dispersion energetics; this allowed the experimental observables to be reproduced by a model that includes only Lennard-Jones parameters. The most energetically favorable H2 sorption site in PCN-14 corresponds to sorption within a small cage that is enclosed by three [Cu2(O2CR)4] units and three adip linkers. The anthracenyl rings of the adip linkers represent the secondary sorption sites within the MOF. In contrast to expectations{,} sorption of H2 onto the Cu2+ ions of the copper paddlewheels was not observed within the simulations at low loading. The simulations revealed that the open-metal sites in PCN-14 were occupied at high loading. Control simulations of H2 sorption in PCN-14 for different cases in which the partial positive charge of one of the paddlewheel Cu2+ ions was increased relative to the other revealed that sorption onto the open-metal sites can be captured if there is a very high positive charge on the metal. Otherwise{,} the calculated partial charge for the Cu2+ ions in PCN-14 in this work was not high enough in magnitude to facilitate strong H2-metal interactions in simulation. This study shows the power of using molecular simulations to elucidate an unusual H2 sorption behavior in a MOF."}