UNIST Develops Porous Material Synthesis Technology with Different Outer and Inner Structures... Expected to Enhance Next-Generation Catalyst and Sensor Performance

Co-first authors Junmo Seong, Seongwook Moon, and Seok Jeong (from left) are taking a group commemorative photo.

[Asia Economy Yeongnam Reporting Headquarters Reporter Hwang Du-yeol] A synthesis technology has been developed that mixes multiple MOF (metal-organic frameworks) materials inside particles in desired forms.

The technology can synthesize both ‘core-shell structures’ where the inside and outside of a particle are made of different materials, and structures where different materials are evenly mixed. Different types of MOFs can also be selectively arranged according to the purpose of the chemical reaction.

UNIST’s Department of Chemistry professors Myungsoo Na and Seungkyu Min’s joint research team published the new MOF synthesis technology in the international journal Nature Communications.

MOFs, which are porous solids, can trap gases inside their pores or selectively capture specific gases, making them next-generation materials attracting attention for gas storage devices, sensors, and catalytic materials.

MOFs consist of multiple basic unit structures connected together, and when the combination of metals and organics forming the unit structure changes, the shape or chemical properties of the unit structure change, resulting in a new type of MOF.

The research team’s technology is a method to control the spatial distribution of the basic unit structures by changing the temperature.

At high temperatures, the A combination unit structure forms only on the outside of the particle, while the B combination unit structure forms only inside the particle, resulting in a core-shell structure.

Conversely, at low temperatures, the A and B unit structures are evenly mixed. Multi-core shell structures composed of multiple core-shell structures are also possible.

The research team also identified the conditions for controlling the spatial distribution of the basic unit structures through their study.

Although several synthesis methods have been developed to control the material distribution within MOF particles, including core-shell forms, the key factors that change material distribution had not been properly understood.

Research on MOF materials revealed that the difference in temperature sensitivity between the exchange rate of the exchanger and the diffusion rate is important.

The method of synthesizing new MOFs by replacing the organics or metals of already synthesized MOF particles with exchangers is called the ‘post-synthetic exchange method.’

This method allows changing only the composition while maintaining the shape of the MOF unit structure, making it easier to synthesize desired MOFs compared to the method of synthesizing MOFs by mixing all raw materials at once.

Junmo Sung, the first author, explained, “The speed at which the exchanger spreads through the MOF structure is less sensitive to temperature, but the reaction where the basic structure’s organics are replaced by the exchanger is more temperature-sensitive. This synthesis method uses that principle,” adding, “Spatial distribution can be controlled simply by temperature adjustment, making it easy to apply.”

Professor Seungkyu Min, who simulated the spatial distribution of materials based on the difference between exchanger exchange rate and diffusion rate, said, “This is an excellent research case where theoretical and experimental results match, and it can serve as a guideline for developing various post-synthetic exchange methods in the future.”

Professor Myungsoo Na said, “If the spatial distribution of unit structures is well controlled, MOF materials tailored to desired purposes can be created,” and expressed expectations that it could be used to develop various MOF-based sensors, catalysts, and gas storage devices.

The research was published online on the 25th and was supported by the Leading Research Center (SRC) program managed by the National Research Foundation of Korea.

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