Structural study of D(2) within the trimodal pore system of a metal organic framework
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Date
2011-05-05
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American Chemical Society
Abstract
D-2 loaded to saturation at 25 K into the porous coordination framework Cu-3(1,3,5-benzenetricarboxylate)(2) was studied using neutron powder diffraction. A saturation loading equivalent to 6.1 wt % H-2 is reached at 25 K. D-2 is located at up to nine distinct sites with six stable at saturation and three "metastable" sites at doses intermediate to saturation. Filling of the trimodal pore system is complex, and a concentration dependency on the optimal D-2 arrangement is noted. A dynamic rearrangement of the D-2 in the pores to a cubic-closed packed equilibrium structure occurs at doses close to saturation, with 4 D-2 molecules arranged tetrahedrally in the smallest pore, 32 D-2 arranged in a truncated octahedron with capped hexagonal faces in the intermediate sized pore, and 48 D-2 arranged in a face-capped rhombic dodecahedron in the largest pore. The equilibrium structure of D-2 in the largest pore at doses close to and at saturation was found to be the same arrangement that is optimal for 48 circles on a sphere. The structural response of the framework to D-2 adsorption is dependent on the amount of D-2, where the host lattice expands with increasing amount of adsorbed D-2 at low and high D-2 doses, and contracts upon adsorption of intermediate amounts of D-2, commensurate with the known flexibility exhibited by this framework. © 2011, American Chemical Society
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Keywords
Metals, Molecules, Thermal expansion, Pore structure, Hydrogen, Neutron diffraction
Citation
Peterson, V.K., Brown, C.M., Liu, Y., Kepert, C.J. (2011). Structural study of D(2) within the trimodal pore system of a metal organic framework. Journal of Physical Chemistry C, 115(17), 8851-8857. doi:10.1021/jp2010937