Densified HKUST-1 Monoliths as a Route to High Volumetric and Gravimetric Hydrogen Storage Capacity.

We are currently witnessing the dawn of hydrogen (H) economy, where H will soon become a primary fuel for heating, transportation, and long-distance and long-term energy storage. Among diverse possibilities, H can be stored as a pressurized gas, a cryogenic liquid, or a solid fuel adsorption onto porous materials. Metal-organic frameworks (MOFs) have emerged as adsorbent materials with the highest theoretical H storage densities on both a volumetric and gravimetric basis. However, a critical bottleneck for the use of H as a transportation fuel has been the lack of densification methods capable of shaping MOFs into practical formulations while maintaining their adsorptive performance. Here, we report a high-throughput screening and deep analysis of a database of MOFs to find optimal materials, followed by the synthesis, characterization, and performance evaluation of an optimal monolithic MOF (MOF) for H storage. After densification, this MOF stores 46 g L H at 50 bar and 77 K and delivers 41 and 42 g L H at operating pressures of 25 and 50 bar, respectively, when deployed in a combined temperature-pressure (25-50 bar/77 K → 5 bar/160 K) swing gas delivery system. This performance represents up to an 80% reduction in the operating pressure requirements for delivering H gas when compared with benchmark materials and an 83% reduction compared to compressed H gas. Our findings represent a substantial step forward in the application of high-density materials for volumetric H storage applications.