The development of safe and efficient H2 storage systems is required for the practical use of H2 as an alternative energy source to fossil fuels. The use of H2 adsorption on porous materials, especially on metal-organic frameworks (MOFs), is one of the most promising methods; however, the H2 uptake of MOFs is limited due to their weak interactions with H2. Recently, it has been shown that Li-doped MOFs can increase their H2 uptake due to a strong interaction between Li and H2.1-3 However, peculiar organic ligands for Li ions should be introduced into the MOF skeleton. 2,3 Therefore, a useful method of Li doping into MOFs should be established. Recently, we have succeeded in Li doping into mesoporous silica based on the release of the anion by the heat treatment after impregnation with an ethanol solution of LiCl.4 The Cl- was released in the form of C2H5Cl as a result of reaction with ethoxy groups on silica. This method is extended to MOFs. In this research, the Li doping into MIL-53(Al), which is a highly thermally-stable MOF constructed from aluminum and terephthalic acid with 1D rhombic channels,5 was investigated impregnation with a LiNO3 solution followed by the heat treatment in vacuum. During the heat treatment, the NO3- were released in the form of NOx, which were detected by in situ FT-IR, while the Li+ remained. The H2 uptake at 77 K and atmosphere pressure increased from 1.63 wt% for the non-doped MIL-53(Al) to 1.76 wt% for the Li-doped MIL-53(Al). Further experimental details will be reported in the presentation.
1. S. S. Han, et al., J. Am. Chem. Soc., 2007, 129, 8422. 2. K. L. Mulfort, et al., J. Am. Chem. Soc., 2007, 129, 9604. 3. D. Himsl, et al., Angew. Chem. Int. Ed., 2009, 48, 4639. 4. N. Chino, et al., J. Phys. Chem. B, 2005, 109, 8574. 5. T. Loiseau, et al., Chem. Eur. J., 2004, 10, 1373.