As an emerging class of crystalline materials, Metal Organic Frameworks (MOFs) might hold extraordinary promise to solve hydrogen storage challenges. However, MOFs are expensive, and their designs and structures rely upon a ‘building block’ approach by combining various metal oxide clusters and multifunctional organic linkers. There is limited flexibility for specific applications and for performance at reasonable cost. The organic linkers that enable high porosities in MOFs are prone to decomposition at elevated temperatures. The open frameworks of MOF built up from the assembly of metal clusters and organic linkers are also vulnerable to water, particularly for defect-rich MOFs. A final intrinsic limitation is that MOFs predominately contain micropores (<2nm), which limit mass transfer. These features have, to date, constrained their real-world implementation, in particular, under the harsh environmental conditions common in Australia.
Our recently developed and published novel mineral-integrated MOF (Cr-MIL-101) composites with diatomite, demonstrate tunable morphologies and sizes with distinctive hierarchical pore structures. The resulting improved adsorptive properties and mass transfer abilities cannot be achieved by either diatomite or MOF or their mixture alone. These mineral-MOF composites show among the highest hydrogen adsorption capacities obtained by MOFs or MOF-composites to date.
Many minerals, including clay minerals, not only play a pivotal and well-established role in nature but have enormous economic value. Using abundant Australian clay minerals and MOFs, this research will build new high performance composite hydrogen storage materials with spatial, dimensional, and structural features superior to current design. The hierarchical structures of the composites (with micro-, meso- and macropores) provide desired topologies to adsorb and desorb high concentrations of hydrogen gas. The fundamental research design targets temperature and humidity stability of the composites while retaining the well-known high gas adsorption and surface properties of individual components (clay minerals and MOFs). This research will discover the underlying formation mechanisms of composite structures and enable their practical and economical uses in future energy industries.
- Wang, Gaofeng, Graham, Elizabeth, Zheng, Shuilin, Zhu, Jianxi, Zhu, Runliang, He, Hongping, Sun, Zhiming, Mackinnon, Ian D.R., Xi, Yunfei (2020) Diatomite-metal-organic framework composite with hierarchical pore structures for adsorption/desorption of hydrogen, carbon dioxide and water vapor. Materials, 13 (21), pp.Article number: 4700.