Coordination polymer flexibility leads to polymorphism and enables a crystalline solid-vapour reaction: a...

Area of Science:

• Materials Science
• Crystallography
• Supramolecular Chemistry

Background:

• Conventional porous materials are typically used for gas absorption.
• Coordination polymers offer tunable structures for host-guest chemistry.

Purpose of the Study:

• To investigate the alcohol absorption capabilities of a non-porous 1D coordination polymer.
• To elucidate the mechanism and structural transformations during guest uptake and release.

Main Methods:

• Single-crystal X-ray diffraction
• Gas-phase IR spectroscopy
• Thermogravimetric Analysis (TGA)
• Differential Scanning Calorimetry (DSC)
• In situ powder X-ray diffraction (PXRD)
• Optical microscopy
• Atomic Force Microscopy (AFM)

Main Results:

• The 1D coordination polymer [Ag4(O2C(CF2)2CF3)4(TMP)3] reversibly absorbs small alcohols (methanol, ethanol, isopropanol) from the vapor phase.
• Reactions proceed via single-crystal-to-single-crystal transformations, forming new coordination polymers [Ag4(O2C(CF2)2CF3)4(TMP)3(ROH)2].
• Four polymorphic forms of the initial polymer were identified, with high-temperature polymorphs playing a role in the absorption/desorption processes.
• Structural analysis revealed pathways for guest transport within fluorous layers, involving conformational changes and polymer reorientation.

Conclusions:

• The study demonstrates a novel mechanism for guest sorption in a non-porous coordination polymer.
• Reversible alcohol absorption is facilitated by structural flexibility and polymorphic transitions.
• The findings provide insights into guest transport mechanisms in layered materials.