Low‐Pressure CO 2 and Aromatic Recognition by Interlayer Adaptive Crystal of π‐Hole‐Functionalized Zn(II) Coordination Sheets

ABSTRACT A layer‐type host, an interlayer adaptive crystal (LAC) constructed from paddle‐wheel Zn(II) nodes, tetrafluoroisophthalate ( L ) linkers, and pyridine (Py) axial ligands, [Zn( L )Py] 2n , exhibits guest‐induced, electrostatically driven breathing. The crystal contains 2.6 Å π‐hole‐defined ultramicropores that act not as classical channels but as electrostatic triggers for guest‐induced single‐crystal‐to‐single‐crystal expansion. Dynamic modulation of interlayer spacing and surface contacts yields exceptional flexibility and molecular selectivity. Tetrafluorophenyl π‐holes generate positive quadrupole fields that drive adsorption through host–host repulsion and strong recognition of guests with negative quadrupole moments. Uniaxial voids occupy 12% of the volume, allowing uptake of molecules larger than the ultramicropore. N 2 , CO 2 , CH 4 , and benzene show type‐I adsorption from very low pressure, incorporating 1.2, 2.0, 1.5, and 1.0 molecules per [Zn( L )Py] 2 unit. CO 2 uptake is accompanied by fully reversible interlayer expansion, while benzene inclusion expands the void space to 186% of that of the guest‐free crystal. CO 2 is preferentially adsorbed over N 2 and CH 4 , corroborated by recognition trends among benzene, trifluorobenzene, and hexafluorobenzene. Guest molecules form one‐dimensional arrays within the expanded lattice, and the breathing two‐dimensional sheet combines the uptake capability of metal‐organic frameworks (MOFs) with the molecular precision of nonporous adaptive crystals (NACs), demonstrating an interaction‐programmed mode of selective molecular inclusion.