Development of Porous Material Synthesis Technology Allowing Control Down to a Single Pore

UNIST Research Team Develops New Technology Using One Type of Chemical Functional Group per Pore in Porous Materials
Supports Development of Metal-Organic Porous Materials Noted for Catalysts and Gas Storage ... Published in Matter

Compared to conventional porous solids where various types of functional groups are randomly arranged (left), a new porous solid was synthesized in which identical functional groups are confined within cages (right). This synthetic strategy, which allows control over the positions of functional groups within the solid, can mix from two types of functional groups to more, forming porous solids with the same structure.

[Asia Economy Reporter Kim Bong-su] A technology has been developed to control the synthesis of porous solids at the level of a single pore.

Ulsan National Institute of Science and Technology (UNIST) announced on the 27th that a research team led by Professors Choi Won-young and Kwon Tae-hyuk from the Department of Chemistry developed a new technology for synthesizing multivariate metal-organic porous solids.

Metal-organic porous solids are pore structures formed by the combination of metals and organic molecules, into which various chemical functional groups can be inserted to alter pore characteristics. The porous solids produced by the developed synthesis method are multivariate porous solids with multiple types of chemical functional groups added, but each pore contains only one type of functional group. This distinction makes it suitable for studying the correlation between the types of chemical functional groups and pore characteristics. It is attracting attention as a technology that can help design customized materials for gas separation and storage, as well as catalytic materials, by utilizing pores.

The developed synthesis technology is based on metal-organic polyhedra (MOPs). MOPs are materials composed of multiple polyhedral cages with open tetrahedral faces loosely connected. These cages consist of metal ions acting as vertices and organic molecules acting as edges. Chemical functional groups bind to the organic molecules.

The research team first synthesized several types of MOPs containing only specific functional groups, then dissolved the synthesized polyhedral cages in a solvent and recrystallized (solidified) them using a two-step synthesis method. By using this two-step synthesis, they were able to synthesize multivariate solids where the entire material contains various types of functional groups evenly, but each pore is composed of a single functional group. In contrast, conventional synthesis methods result in multiple functional groups mixed within a single pore structure.

A team member explained, “The key strategy of this synthesis method is that metal-organic polyhedra can be dissolved in a solvent and recrystallized as polyhedral cage units. Typically, metal-organic polyhedra change their cage framework structure when the type of functional group changes, but the synthesized material maintained its structure, which is very unusual.”

Because the synthesized material maintains its structure even when the chemical functional groups change, it serves as a suitable platform for studying physical properties according to the type of functional group. The research team verified this by synthesizing multivariate porous solids using both the developed and conventional synthesis methods. In the conventional method, functional groups are randomly positioned on the edges of the polyhedral cages, resulting in various combinations of polyhedral cages. However, in the new synthesis method, only cage types matching the number of added functional group types were detected. Mass spectrometry was used for analysis, based on detecting weight differences depending on the functional groups composing the polyhedra.

The team also compared the luminescent properties of MOPs made by the two synthesis methods. Although the ratio of functional groups composing the solid was the same, they exhibited different fluorescence emission characteristics. This demonstrated that differences in the arrangement of functional groups can lead to differences in photophysical properties.

Professor Choi Won-young said, “This technology is valuable for identifying pore characteristics based on the composition of functional groups by varying the functional group composition in each pore,” and added, “By inserting various chemical functional groups into the pore structure, it will be possible to find pore characteristics optimized for specific application goals.”

The research results were published in the June 26 issue of Matter, a sister journal of Cell.

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