Gate-opening Induced by C8 Aromatics in a Double Diamondoid Coordination Network

Area of Science:

• Materials Science
• Supramolecular Chemistry
• Chemical Engineering

Background:

• Coordination networks (CNs) are investigated for their potential in separations and storage.
• Guest-induced structural transformations in CNs are of significant interest.
• Developing materials with tunable properties for specific applications is crucial.

Purpose of the Study:

• To synthesize and characterize a novel double diamondoid (ddi) topology coordination network, X-ddi-2-Ni.
• To investigate the structural transformations of X-ddi-2-Ni upon exposure to C8 isomers (xylenes and ethylbenzene).
• To evaluate the C8 isomer uptake capacity and selectivity of the transformed coordination network.

Main Methods:

• Single-crystal X-ray diffraction was used to characterize the structural transformations.
• Nuclear Magnetic Resonance (NMR) and Gas Chromatography (GC) were employed to assess isomer uptake and selectivity.
• Dynamic Vapor Sorption (DVS) was utilized to determine gate-opening pressures.
• Computational modeling supported crystallographic findings.

Main Results:

• A ddi topology CN, X-ddi-2-Ni, was synthesized and characterized.
• Single-crystal to single-crystal transformations were observed upon guest inclusion of C8 isomers (OX, MX, PX, EB).
• The material exhibited high C8 isomer uptake (ca. 50 wt %) but low selectivity.
• Dynamic vapor sorption revealed narrow gate-opening pressure ranges, indicating a nonadaptable host framework.

Conclusions:

• X-ddi-2-Ni demonstrates guest-induced structural transformations with C8 isomers.
• The material possesses high C8 isomer accommodation capacity.
• The nonadaptable nature of the C8-loaded phases limits selectivity, despite structural changes.
• Further research may focus on modifying the framework to enhance selectivity for separation applications.