High-Pressure Insertion of Dense H2 into a Model Zeolite.

Wan Xu,Eugene Gregoryanz,Miriam Peña-Alvarez,Mario Santoro,Hua-Chao Jiang,Julien Haines,Benoit Coasne,Xiao-Di Liu,Philip Dalladay-Simpson

doi:10.1021/acs.jpcc.1c02177

Abstract

Our combined high-pressure synchrotron X-ray diffraction and Monte Carlo modeling studies show super-filling of the zeolite, and computational results suggest an occupancy by a maximum of nearly two inserted H2 molecules per framework unit, which is about twice that observed in gas hydrates. Super-filling prevents amorphization of the host material up to at least 60 GPa, which is a record pressure for zeolites and also for any group IV element being in full 4-fold coordination, except for carbon. We find that the inserted H2 forms an exotic topologically constrained glassy-like form, otherwise unattainable in pure hydrogen. Raman spectroscopy on confined H2 shows that the microporosity of the zeolite is retained over the entire investigated pressure range (up to 80 GPa) and that intermolecular interactions share common aspects with bulk hydrogen, while they are also affected by the zeolite framework.

Highlights

We focused our work on a model, pure SiO2 zeolite, silicalite-1 in order to avoid catalytic effects and to investigate how the pore size and shape affect the topology of the confined molecular form under pressure
Based on synchrotron X-ray diffraction (XRD) and Monte Carlo (MC) modelling, we show that the insertion leads to an exotic glassy-like form of molecular hydrogen
Powder XRD patterns of H2-filled silicalite-1 were measured upon increasing pressure up to 60 GPa (Figure 2), in order to investigate to which extent the framework is stable at high pressures and to provide inputs for Monte Carlo modelling aimed to determine the amount of stored hydrogen

Summary

Introduction

We focused our work on a model, pure SiO2 zeolite, silicalite-1 in order to avoid catalytic effects and to investigate how the pore size and shape affect the topology of the confined molecular form under pressure.

Results

Conclusion