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, NiL₂ (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 NiL₂ approaches that of compressed natural gas but at much lower pressures. The guest-induced phase transitions of NiL₂ 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 NiL₂ . Specifically, the extended linker ligand, L, undergoes ligand contortion and interactions between interpenetrated networks or sorbate-sorbent interactions enable the observed switching.