Researchers Develop Unique Pillar-Cage Framework for Gas Separation

A team of researchers led by Prof. Wu Mingyan from the Fujian Institute of Research on the Structure of Matter, part of the Chinese Academy of Sciences, has introduced a novel approach to synthesizing a unique pillar-cage fluorinated hybrid porous framework named TIFSIX-Cu-J. This framework features a rare crystalline structure known as the quasi-Johnson solid J28, which may have significant implications for gas separation technologies.

The study, published on November 5, 2025, in the journal Chem, details how the researchers created TIFSIX-Cu-J using a bottom-up, self-assembly methodology. This method incorporates geometrical elements of quadrangles and isosceles triangles, leading to a highly organized porous structure. Notably, TIFSIX-Cu-J can undergo a heat-triggered structural transformation, where the initial J28 cage reconfigures into a new distorted square orthobicupola structure.

Significant Findings on Adsorption Capacity

Through a combination of single-crystal-to-single-crystal (SC-SC) transformation studies and bulk crystalline powder X-ray diffraction analysis, the research team elucidated the structural changes of TIFSIX-Cu-J. The findings revealed that TIFSIX-Cu-J1, a variant of the framework, achieved an impressive adsorption capacity of 140.5 cm³·g⁻¹ for propylene (C3H6). Furthermore, the difference in adsorption amounts between propylene and propene increased from 19.6 cm³·g⁻¹ to 34.8 cm³·g⁻¹.

The selectivity of TIFSIX-Cu-J1 was found to be superior, yielding a higher C3H4/C3H6 ideal adsorbed solution theory (IAST) selectivity compared to its predecessor TIFSIX-Cu-J. In practical applications, in-situ breakthrough experiments demonstrated that a packed column of TIFSIX-Cu-J1 could directly produce a significantly higher C3H6 output—approximately twenty times greater than that of TIFSIX-Cu-J.

Implications for Energy-Efficient Gas Purification

The research indicates that the optimized pore surface within the quasi-Johnson solid J28 cavity of TIFSIX-Cu-J1 preferentially captures propylene over propene. This characteristic enhances the selective separation capabilities of the framework, potentially making it valuable for energy-efficient gas purification processes.

This study not only contributes new insights into the design and synthesis of advanced porous frameworks but also emphasizes the effectiveness of the bottom-up, self-assembly approach in constructing artificial cage-like three-dimensional architectures with selective separation properties.

As the field of gas separation continues to evolve, the developments around TIFSIX-Cu-J and its variants could pave the way for novel applications in various industrial separation scenarios, underscoring the importance of innovative materials in addressing energy efficiency challenges.

For further details, refer to the original publication by Cheng Chen and colleagues in Chem.