Nanotechnologies / Materials
Carbon neutral, Energy storage, Sensing devices

Adsorption, separation, and storage of gas molecules through the development of organic
porous materials that can be shape-controlled and surface-modified
Department of Applied Chemistry, Graduate School of Engineering
Professor Norimitsu Tohnai

https://researchmap.jp/read0089607

Assistant Professor Kouki Oka

https://researchmap.jp/k.oka

Abstract

Nanotechnologies / Materials

Organic porous materials are increasingly being applied not only
for adsorption, separation, purification, and catalyst, but also forvarious applications such as sensors and imaging by adding optic,electronic and magnetic properties.
Our research group has proposed a new organic porous material called porous organic salts (POS). In this study, we modified theporous surfaces of POS with various halogen elements, and wereable to change the adsorption properties, such as selectivity togas molecules and adsorption amount, depending on the halogenelements.

age of green energy such as hydrogen and ammonia; and sensitive and highly selective sensing and recovery of toxic substancessuch as dioxin, PFOA, and PFOS.

▍ Background & Results
Inorganic porous materials have long been used in various fields
such as storage, separation, purification, and catalysts. However,there are limits to the materials, structures, and properties that canbe used, and over the past 20 years, organic porous materials withorganic components have been actively investigated.
Among them, POSs presented by our group are constructed bysimply mixing acidic and basic molecules, and can be produced
very easily. The size, shape, and surface properties of the pores
can be controlled by designing each component. Furthermore, it iseasy to add optic, electronic and magnetic properties and can beapplied to a variety of sensors and imaging. Additionally, they canbe easily reused by washing or chemically regenerated by decomposition, contributing to the development of sustainable materials.
In this study, we constructed a porous structure of porous organic salts with hydrogen and four halogen elements exposed on
the surface of the pores. The hydrogen-exposed porous material
selectively adsorbed only carbon dioxide. On the other hand, thefluorine-exposed porous material adsorbed more carbon dioxideand was also able to adsorb oxygen and nitrogen. Furthermore, thechlorine-exposed material changed its selectivity for gas molecules
and adsorbed oxygen best. As described above, by controllingthe chemical environment of the pore surface, we succeeded inchanging the adsorption properties for chemical substances.

Fig.-1 Hierarchical construction of porous organic salts

Fig.-2 Gas adsorption behavior of various porous organic salts▍ Significance of the research and Future perspective
Our porous organic salts can be chemically modified in termsof the shape and size of the vacancies and their surfaces. In thiswork, we have achieved modification of the pore surfaces with halogen elements and demonstrated that the properties of the porous
materials can be controlled.
It is noteworthy that the amount of adsorption, selectivity, andmolecular recognition ability can be controlled. Such chemical
modification is also possible with other substituents and elements,
and can be deployed in various applications such as the recovery
and separation of gaseous species that have a negative impact on
global warming, such as carbon dioxide, methane, and CFCs; stor-Fig.-3 Porous structures depending on various halogen elements

P a t e n tAmi, Takahiro; Oka, Kouki; Tohnai, Norimitsu et al. Porous Organic Salts: Diversifying Void Structures and Environments, Angew. Chem., Int. Ed., 2022, 61,e202202597, doi: 10.1002/anie.202202597
UR
L http://www.chem.eng.osaka-u.ac.jp/~tohnaiken/scientific/
K e y w o r d organic porous materials, surface modification, CO2 capture, sensing
Tr e a t i s e