Modulated synthesis of Cr-MOF (MIL 101) for hydrogen storage applications

Abstract

With the increasing environmental pressures, alternative sources of energy are required. Hydrogen has long been considered to be an ideal alternative to fossil fuel system owing to its elimination of greenhouse gasses. Complete usage of hydrogen as a fuel into fuel cell technologies is only possible when safe and effective hydrogen storage systems become available. Complete usage of hydrogen is only possible if proper and effective storage systems with fast kinetics becomes available. Porous material-based adsorptive storage, hydrogen gas as an adsorbed species within a suitable porous adsorbent such as metal organic frameworks (MOFs), continue to attract an increasing attention as a long-term solution to meet stringent volumetric targets and offer low-pressure hydrogen storage [1]. Among the various MOFs materials, Chromium-based MOF (MIL-101) has shown to pose high surface area, good stability and comparable hydrogen storage capacities. However, its current synthesis procedure incudes the use of very toxic and dangerous chemicals such as Hydrofluoric acid (HF)[2]. In this work, MIL-101 crystals with high crystallinity and well-defined shapes were synthesised using water as solvent and small amount of formic acid as modulator. The obtained MIL-101 products showed excellent hydrostability, high porosity and big surface area, making it particularly suitable for practical hydrogen storage applications. The synthesis procedure employed in this study has also been proved to be a far safer way of synthesising MIL 101 with properties comparable to those of MIL-101 synthesised when using HF as the modulator.