Post‐synthetic modification unlocks a 2D‐to‐3D switch in MOF breathing response: a single‐crystal‐diffraction mapping study

Post-synthetic modification (PSM) of the interpenetrated diamondoid metal-organic framework (Me 2 NH 2 )[In(BDC-NH 2 ) 2 ] (BDC-NH 2 = aminobenzenedicarboxylate) SHF-61 proceeds quantitatively in a single-crystal-to-single-crystal manner to yield the acetamide derivative (Me 2 NH 2 )[In(BDC-NHC(O)Me) 2 ] SHF-62 . Continuous breathing behaviour during activation/desolvation is retained upon PSM, but pore closing now leads to ring-flipping to avert steric clash of amide methyl groups of the modified ligands. This triggers a reduction in the amplitude of the breathing deformation in the two dimensions associated with pore diameter, but a large increase in the third dimension associated with pore length. The MOF is thereby converted from predominantly 2D breathing (in SHF-61 ) to a distinctly 3D breathing motion (in SHF-62 ) indicating a decoupling of the pore-width and pore-length breathing motions. These breathing motions have been mapped by a series of single-crystal diffraction studies