Decoupled MOF Breathing: Pressure‐Induced Reversal of Correlation Between Orthogonal Motions in a Diamondoid Framework

Abstract

Abstract Responsive porous materials can outperform more rigid analogues in applications requiring precise triggering of molecular uptake/release, switching or gradual change in properties. We have uncovered an unprecedented dynamic response in the diamondoid MOF SHF‐62 , (Me 2 NH 2 )[In(BDC‐NHC(O)Me) 2 ] (BDC = 1,4‐benzenedicarboxylate), by using pressure as a stimulus. SHF‐62 exhibits two distinct framework “breathing” motions involving changes in 1) cross‐section and 2) length of its 1D pores. Our study using synchrotron single‐crystal X‐ray diffraction in sapphire‐capillary ( p  < 0.15 GPa) and diamond‐anvil (0.15 <  p < 5 GPa) cells reveals that different pressure regimes trigger positive and negative correlation between these two motions, requiring an unprecedented mechanical decoupling. Specifically, the DMF‐solvated framework SHF‐62‐DMF , in DMF as pressure‐transmitting medium, undergoes initial hyperexpansion of pore cross‐section ( p  ≤ 0.9 GPa), due to DMF ingress, followed by reversal/reduction at p  > 0.9 GPa while pore length contracts for all pressure increases, revealing decoupling of the two framework deformations. By contrast, nonpenetrating medium FC‐70 imposes correlated compression ( p  < 1.4 GPa) of pore cross‐section and length, resembling framework activation/desolvation motions but of greater magnitude. Similar behavior occurs for SHF‐62‐CHCl 3 in CHCl 3 ( p  < 0.14 GPa), suggesting minimal ingress of CHCl 3 . These findings change our understanding of MOF dynamic responses and provide a platform for future responsive materials development.