Soft Porous Crystal Based upon Organic Cages That Exhibit Guest-Induced Breathing and Selective Gas Separation

Area of Science:

• Materials Science
• Supramolecular Chemistry
• Chemical Engineering

Background:

• Soft porous crystals (SPCs) are materials with dynamic sorption capabilities, but their design and synthesis are complex.
• Stimuli-responsive behavior in SPCs is crucial for applications in gas storage and separation.

Purpose of the Study:

• To report a novel imide-based organic cage, NKPOC-1, as a new type of soft porous crystal.
• To investigate the guest-induced breathing behavior and gas sorption properties of NKPOC-1.
• To evaluate the potential of NKPOC-1 for selective C3 hydrocarbon separation.

Main Methods:

• Synthesis of the imide-based organic cage NKPOC-1.
• Gas sorption experiments to observe guest-induced phase transitions (α, β, γ).
• Fixed bed column breakthrough experiments for separation performance evaluation.
• In situ X-ray diffraction and molecular dynamics simulations to study structural transformations and adsorption energies.

Main Results:

• NKPOC-1 exhibits reversible gate-opening behavior upon exposure to CO2 and C3 hydrocarbons, switching between nonporous (α) and porous (β, γ) phases.
• NKPOC-1-α demonstrates selective adsorption of propyne over propylene and propane under ambient conditions.
• Separation of binary and ternary C3 hydrocarbon mixtures was successfully verified.
• Structural transformations correlate with gate-opening effects, supported by diffraction and simulation data.

Conclusions:

• NKPOC-1 represents a new class of soft porous crystals with tunable, guest-induced dynamic sorption.
• The material shows significant potential for selective C3 hydrocarbon separation, particularly propyne.
• The study provides insights into structure-property relationships in dynamic soft porous materials, advancing their application in gas separation and storage without recyclability issues.