Light and Guest Responsive Behavior in a Porous Coordination Network Enabled by Reversible [2+2] Photocycloaddition

Area of Science:

• Materials Science
• Chemistry
• Nanotechnology

Background:

• Stimuli-responsive materials are crucial for advanced gas storage and separation technologies.
• Existing research primarily focuses on materials responding to single stimuli (light or guests), limiting their application scope.
• There is a need for sorbents exhibiting combined light and guest-induced structural transformations.

Purpose of the Study:

• To report a novel coordination network material with dual light and guest-responsive properties.
• To investigate the single-crystal-to-single-crystal transformations induced by external stimuli.
• To explore the potential of this material in gas separation and storage applications.

Main Methods:

• Synthesis and characterization of the coordination network Zn(fba)(bis)⋅2DMF (sql-5,6-Zn-α).
• Investigation of single-crystal-to-single-crystal (SCSC) transformations upon activation, light exposure, and guest interaction.
• In situ Powder X-ray Diffraction (PXRD), single-crystal X-ray Diffraction (XRD), and 1H NMR spectroscopy for structural analysis.

Main Results:

• The coordination network sql-5,6-Zn-α undergoes SCSC transformations upon activation and light-induced [2+2] photocycloaddition, forming mot-5,6-Zn-α.
• Both activated phases (sql-5,6-Zn-β and mot-5,6-Zn-β) exhibit guest-induced structural changes upon CO2 adsorption, displaying characteristic S-shaped isotherms.
• Cycling experiments revealed a transformation into a shape memory coordination network (sql-5,6-Zn-γ).

Conclusions:

• A novel coordination network material demonstrating coupled light and guest-induced structural transformations has been developed.
• The material exhibits reversible SCSC transformations and unique adsorption behaviors, including a shape memory effect.
• This work expands the design principles for stimuli-responsive materials for gas storage and separation.