Highly Porous Metal-Organic Framework Containing a Novel Organosilicon Linker - A Promising Material for Hydrogen Storage

The synthesis and characterization of the new metal-organic framework PCN-12-Si (isoreticular to PCN-12) is reported. PCN-12-Si comprises dicopper paddle-wheel units located at the vertices of a cuboctahedron, which are connected by the new linker 5,5'-(dimethylsilanediyl)diisophthalate (dmsdip). The microporous MOF has a high specific surface area of S-BET = 2430 m(2) g(-1) and a high specific micropore volume of V-p = 0.93 cm(3) g(-1) (p/p(0) = 0.18). The activated form of PCN-12-Si shows a remarkable hydrogen storage capacity. Volumetric low pressure hydrogen physisorption isotherms at 77 K reveal an uptake of 2.6 wt % H-2 at 1 bar. Furthermore, results of theoretical GCMC simulations of hydrogen adsorption are presented. The simulated low pressure isotherm is in excellent agreement with the experimental one. Simulations for the high pressure regime predict an excess hydrogen uptake of 4.8 wt % at 30 bar, which corresponds to an absolute amount adsorbed of 5.5 wt %. In addition, the potential field of H-2 inside PCN-12-Si was derived from the simulations and analyzed in detail, providing valuable insights concerning the preferred adsorption sites on an atomic scale.