High H2 Adsorption by Coordination-Framework Materials

The storage of H2 in a safe and compact form represents a significant current challenge,[1] and there is wide-ranging interest in materials that can store and release H2 with fast kinetics and high reversibility over multiple cycles.[2] Porous coordination frameworks have become competitors to other porous materials, such as zeolites[3] and carbon materials (for example, activated carbon or nanotubes),[4] with recent studies confirming that these frameworks can store considerable quantities of H2 at 78 K.[5–11] Most studies of H2 adsorption in coordination frameworks focus on the lowpressure region (0–1 bar) and, therefore, do not fully address the relationship between porosity and storage capacity. Although recent high-pressure volumetric measurements on some coordination frameworks revealed a correlation between maximum uptake and surface area,[9] the study involved several coordination frameworks with different structure types, and the influence of pore size and shape on guest adsorption was not investigated systematically. Herein, we report the structures of three close structural analogues, along with studies of high-pressure H2 adsorption by these materials, to establish a route to higher H2 storage capacity.