Prof. Koh’s group conceived a feasible route for developing a scalable platform for CO2 capture (including direct air capture) using metal-organic frameworks. MOF-based fiber sorbents show high CO2 uptake and low pressure drop for long-term cyclic operation in direct air capture mode.

Nanoporous materials can enable low-energy separation processes due to their superb textural properties, yet these materials face practical challenges in large-scale applications. Prof. Koh’s group at KAIST has developed a feasible route for creating a scalable platform for CO2 capture using metal-organic framework-based fiber sorbents. The study was published on July 17th in Chemistry of Materials (Chem. Mater. 2020, 32, 17, 7081–7104). The paper was selected as a cover article. As a part of the “Up-and-Coming” series published in ACS publications, Prof. Koh was chosen as one of the “Up-and-Coming Researchers” at Chemistry of Materials in 2020.

“Continuous advancements in nanoporous materials will one day eliminate the gap of scale between those of a lab and the industry” said Dong-Yeun Koh, paper author and assistant professor of Chemical and Biomolecular Engineering at KAIST. Such progress would dramatically increase the chances of the feasibility of integrating high-performance materials and scalable separation devices.

Fiber Sorbents, fabricated from traditional “fiber spinning technology” adopted from the textile industry, are a next-generation platform for adsorptive separations. This material has a scalable architecture that integrates porous materials into a fluid contactor. With a multi-filament (e.g., multiple spinnerets used in the textile industry) approach, industrial-scale fabrication of fiber sorbents is possible (over 50 meters per minute). A fluid contactor module produced with fiber sorbents should be able to process high-gas flow rates with a low-pressure drop, minimizing the operating costs in CO2 capture. Besides this, fiber sorbents have better mass/heat transfer coefficients than those of conventional systems. Therefore, it is possible to build more productive and smaller separation devices.

Despite the steady development of the adsorption capacity and stability by functionalizing sorbents in type 1 fiber sorbents, there is a significant need for the development of technologies that can dramatically improve the performance of fiber sorbents. To address this need, Prof. Koh’s group proposed various candidate materials and a new configuration of type 2 or 3 fiber sorbents generated from various post-spinning conversions such as MOF conversion, secondary growth, and calcination/sintering processes. The controlled dissolution of the surface metal oxide layer through a mild synthesis solution containing long-chain linkers inside the mesoscopic space provided by polymer supports enabled the formation of highly uniform Mg-based MOFs in the polymeric support. The mesoscopic confinement effect regulated a precise balance between the surface oxide etching and MOF nucleation. Under humid flue gas emissions, the MOF fiber sorbents selectively capture CO2 with impressive cyclic productivities.

Furthermore, these MOF fiber sorbents could show unprecedented direct air capture (DAC, 400 ppm CO2) capacity in a structured contactor platform.

With continued research on the above requirements, we anticipate that these fiber sorbents will be promising not only for adsorptive separation but also for energy storage, catalysis, gas sensors, etc. Similar to the case of gas separation membranes, developing a scalable “next-generation fiber sorbent” will truly revolutionize energy-efficient separations.
2021 KI Newsletter