Metal Doping to Control Gate Opening and Increase Methane Working Capacity in Isostructural Flexible Diamondoid Networks

Adsorbed natural gas (ANG) systems involve using porous materials to increase the working capacity and/or reduce the storage pressure compared to compressed natural gas (CNG). Flexible metal-organic materials (FMOMs) are particularly interesting in this context since their stepped isotherms can afford increased working capacity if the adsorption/desorption steps occur within the proper pressure range. We report herein that metal doping in a family of isostructural FMOMs, ML2 (M=Co, Ni or NixCo1-x, L=4-(4-pyridyl)-biphenyl-4-carboxylic acid), enables control over the gate opening between non-porous (closed) and porous (open) phases at pressures relevant to methane storage. Specifically, methane-induced phase transformations can be fine-tuned by using different Ni/Co ratios to enhance methane working capacity. The optimal working capacity from 5 to 35 bar at 298 K (153 cm(3) cm(-3)) was found for Ni0.89Co0.11L2 (X-dia-1-Ni0.89Co0.11), which is greater than that of benchmark rigid MOFs.

Automated summary

Adsorbed natural gas (ANG) systems using porous materials can increase working capacity and reduce storage pressure. Metal doping in flexible metal-organic materials (FMOMs) allows control over the gate opening between porous and non-porous phases, enhancing methane working capacity. Ni0.89Co0.11L2 (X-dia-1-Ni0.89Co0.11) exhibited the highest working capacity of 153 cm(3) cm(-3) at 298 K, surpassing benchmark rigid MOFs.