A pillared-layer coordination polymer with a rotatable pillar acting as a molecular gate for guest molecules

Area of Science:

• Materials Science
• Supramolecular Chemistry
• Crystallography

Background:

• Designing porous coordination polymers (PCPs) with tailored pore properties is crucial for advanced functionalities.
• Flexible motifs and functional groups are key to achieving desired PCPs.
• Understanding guest-framework interactions is essential for developing responsive materials.

Purpose of the Study:

• To synthesize and characterize a novel 3D pillared-layer coordination polymer with a molecular gate.
• To investigate the framework's flexibility and guest-responsive behavior.
• To explore the material's gas sorption properties and potential applications.

Main Methods:

• Single-crystal X-ray diffraction to determine structural transformations.
• Gas adsorption isotherm measurements (H2O, CO2, N2, O2) at various temperatures.
• Analysis of guest inclusion effects on framework dynamics.

Main Results:

• A 3D coordination polymer {[Cd(2)(pzdc)(2)L(H(2)O)(2)].5(H(2)O).(CH(3)CH(2)OH)}(n) was synthesized, featuring a rotatable pillar acting as a molecular gate.
• Reversible single-crystal-to-single-crystal transformations were observed upon guest molecule removal/rebinding.
• The material demonstrated selective CO2 uptake over N2 and O2, and stepwise water adsorption linked to framework functions.

Conclusions:

• The synthesized material functions as a molecular gate with a locking/unlocking system, enabling gate-opening sorption profiles.
• Framework flexibility, including pillar rotation and layer slippage, is key to its responsive behavior.
• The study provides fundamental insights into guest-sorption mechanisms in dynamic porous materials.