Storage of molecular hydrogen into ZSM-5 zeolite in the ambient atmosphere by the sealing of the micropore outlet

•Hydrogen was stored into ZSM-5 in the ambient atmosphere for a few months.•The sealing of the micropores outlet is essential for the hydrogen storage.•Remarkable hysteresis between the sorption branches showed narrowed micropore.•The amount of hydrogen stored was calculated to 0.015 wt% from the released hydrogen over 150 °C.

The storage of molecular hydrogen into ZSM-5 zeolite in the ambient atmosphere was examined by hydrogen filling into the micropore and the following sealing of the micropore outlet to prevent the release of hydrogen to the outside. The surface grafting of 1,4-bis(hydroxydimethylsilyl)benzene onto ZSM-5 zeolite was applied to the sealing of the micropore outlet. Pressurized hydrogen (10 MPa) was filled into the micropore of ZSM-5 at liquid nitrogen temperature (−196 °C), and then the sample was heated at 150 °C for forming strong binding between the zeolite surface and the disilane compound under the hydrogen pressure. The hydrogen sorption isotherm at −196 °C showed that the adsorption of hydrogen onto the disilane-grafted ZSM-5 thus obtained was reduced to less than 20% from the original ZSM-5. The remarkable hysteresis between the adsorption and desorption branches of the isotherm indicated that the kinetic trap of hydrogen occurred by the narrowed outlets of the micropores of ZSM-5 with the disilane compound. Even after exposing the disilane-grafted ZSM-5 to the atmosphere over a few months, hydrogen could be discharged by heating over 150 °C. This result demonstrated that molecular hydrogen was successfully stored into ZSM-5 zeolite in the ambient atmosphere for a long time.

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