Fig. 1
From: A dynamic and multi-responsive porous flexible metal–organic material
The multi-dynamic nature of X-pcu-1-Zn is exemplified by six structurally characterised phases. a Structures of 4,4'-bis(4-pyridyl)biphenyl (L2) and 4,4′-biphenyldicarboxylic acid (L1), the pillaring of the 2D square-grid of [Zn2(L1)2] by L2 affords the observed pcu topology network. b Breathing, X-pcu-1-Zn-3i-α transforms to X-pcu-1-Zn-3i-β and X-pcu-1-Zn-3i-γ; change in the level of interpenetration, X-pcu-1-Zn-3i-β and X-pcu-1-Zn-3i-γ convert to X-pcu-1-Zn-4i when heated at 130 °C; shape memory, X-pcu-1-Zn-3i-α exposed to air followed by heating affords X-pcu-1-Zn-3i-δ; structural isomerism: square-pyramidal Zn atoms in X-pcu-1-Zn-3i-α convert to distorted tetrahedral Zn atoms in X-pcu-2-Zn-3i after solvent exchange with acetonitrile followed by heating. X-pcu-2-Zn-3i, transforms into X-pcu-1-Zn-3i-δ upon further heating. With the exception of X-pcu-1-Zn-4i, all phases revert to X-pcu-1-Zn-3i-α after soaking in DMF for 5 min. X-pcu-1-Zn-4i, the densest phase, is the only phase that is thermodynamically stable under the conditions studied and is highlighted above. The interpenetrated networks are coloured green, maroon red, blue, and purple
