Reversible Switching between Highly Porous and Nonporous Phases of an Interpenetrated Diamondoid Coordination Network That Exhibits Gate‐Opening at Methane Storage Pressures.

Abstract: Herein, we report that a new flexible coordination network, <bold>NiL₂</bold> (L=4‐(4‐pyridyl)‐biphenyl‐4‐carboxylic acid), with diamondoid topology switches between non‐porous (closed) and several porous (open) phases at specific CO₂ and CH₄ pressures. These phases are manifested by multi‐step low‐pressure isotherms for CO₂ or a single‐step high‐pressure isotherm for CH₄. The potential methane working capacity of <bold>NiL₂</bold> approaches that of compressed natural gas but at much lower pressures. The guest‐induced phase transitions of <bold>NiL₂</bold> were studied by single‐crystal XRD, in situ variable pressure powder XRD, synchrotron powder XRD, pressure‐gradient differential scanning calorimetry (P‐DSC), and molecular modeling. The detailed structural information provides insight into the extreme flexibility of <bold>NiL₂</bold>. Specifically, the extended linker ligand, <bold>L</bold>, undergoes ligand contortion and interactions between interpenetrated networks or sorbate–sorbent interactions enable the observed switching. [ABSTRACT FROM AUTHOR]