Regulating the C ₃ H ₆ ‐Induced Gate‐Opening Effect in Pillar‐Layered Metal–organic Frameworks for C ₃

ABSTRACT

The introduction of functional groups onto the ligands of flexible metal–organic frameworks (MOFs) enables the precise modulation of structural flexibility, allowing for the systematic tuning of gate‐opening pressures for specialized gas separation. Herein, by precise regulation of the number and substitution positions of methyl groups in Zn(BDC‐x)(Bipy‐x) _0.5 , a new class of functionalized frameworks was successfully developed. Modulating the framework phase‐transition energy barrier by tuning the position and number of the methyl groups led to a dramatic shift in the C ₃ H ₆ and C ₃ H ₈ gate‐opening pressures. By rationally optimizing the structural flexibility and gate‐opening characteristics, we obtained TYUT‐28, a benchmark material capable of complete discrimination between C ₃ H ₆ and C ₃ H ₈ . At 318 K and 0.5 bar, the optimized framework achieved a high C ₃ H ₆ uptake (32 cm ³  g ⁻¹ ) and a C ₃ H ₆ /C ₃ H ₈ uptake ratio of 17.5. The C ₃ H ₆ ‐induced structural transition was elucidated using high‐resolution synchrotron X‐ray diffraction and microcrystal electron diffraction. The gate‐opening behavior of C ₃ H ₆ and C ₃ H ₈ during adsorption was further investigated by in situ variable‐pressure X‐ray diffraction and in situ infrared analysis. This work highlights methyl substitution as an effective handle for tuning adsorption‐induced flexibility and gate‐opening pressure, enabling efficient C ₃ H ₆ /C ₃ H ₈ separation.