Chapter 10
The Design of Porous Organic Salts
with Hierarchical Process
Norimitsu Tohnai
Abstract Porous organic materials have attracted significant attention due to their
design flexibility and functional versatility. Recently, a new and widely applicable
strategy for the efficient construction of versatile porous organic materials using
organic salts containing triphenylmethylamine (TPMA) and sulfonic acids was
reported. Combinations of TPMA and sulfonic acids with polyaromatic moieties
represent a new class of porous structures consisting of diamondoid networks, termed
diamondoid porous organic salts (d-POS) herein. In a d-POS, the TPMA and sulfonic
acid assemble into stable tetrahedral supramolecular clusters through charge-assisted
hydrogen bonding, representing the initial building blocks. These clusters subsequently accumulate via π-π interactions between polyaromatic moieties, such that
the d-POS is generated. As a result of the significant steric hindrance associated
with such clusters, the diamondoid network cannot build a highly interpenetrating
structure, resulting in the formation of continuous open channels. It should be noted
that the extent of interpenetration in the diamondoid networks can be controlled by
adjusting the bulkiness of the clusters by changing the sulfonic acid. Anthracene2-sulfonic acid (2-AS) builds a three-fold structure with one-dimensional channels,
while pyrene-1-sulfonic acid produces a two-fold structure with two-dimensional
channels. In addition, organic salts composed of TPMA and 2-AS also provide polymorphic structures depending on the ratio of pores to template molecules and the
template species. These structures demonstrate the stability and flexibility of d-POS
materials.
Keywords Organic salt · Charge-assisted hydrogen bond · Porous structure ·
Diamondoid network · Crystal engineering
N. Tohnai (B)
Department of Applied Chemistry, Graduate School of Engineering, Osaka University,
Yamadaoka 2-1, Suita, Osaka 565-0871, Japan
e-mail: tohnai@chem.eng.osaka-u.ac.jp
© Springer Nature Singapore Pte Ltd. 2020
M. Sakamoto and H. Uekusa (eds.), Advances in Organic Crystal Chemistry,
https://doi.org/10.1007/978-981-15-5085-0_10
185
The Design of Porous Organic Salts
with Hierarchical Process
Norimitsu Tohnai
Abstract Porous organic materials have attracted significant attention due to their
design flexibility and functional versatility. Recently, a new and widely applicable
strategy for the efficient construction of versatile porous organic materials using
organic salts containing triphenylmethylamine (TPMA) and sulfonic acids was
reported. Combinations of TPMA and sulfonic acids with polyaromatic moieties
represent a new class of porous structures consisting of diamondoid networks, termed
diamondoid porous organic salts (d-POS) herein. In a d-POS, the TPMA and sulfonic
acid assemble into stable tetrahedral supramolecular clusters through charge-assisted
hydrogen bonding, representing the initial building blocks. These clusters subsequently accumulate via π-π interactions between polyaromatic moieties, such that
the d-POS is generated. As a result of the significant steric hindrance associated
with such clusters, the diamondoid network cannot build a highly interpenetrating
structure, resulting in the formation of continuous open channels. It should be noted
that the extent of interpenetration in the diamondoid networks can be controlled by
adjusting the bulkiness of the clusters by changing the sulfonic acid. Anthracene2-sulfonic acid (2-AS) builds a three-fold structure with one-dimensional channels,
while pyrene-1-sulfonic acid produces a two-fold structure with two-dimensional
channels. In addition, organic salts composed of TPMA and 2-AS also provide polymorphic structures depending on the ratio of pores to template molecules and the
template species. These structures demonstrate the stability and flexibility of d-POS
materials.
Keywords Organic salt · Charge-assisted hydrogen bond · Porous structure ·
Diamondoid network · Crystal engineering
N. Tohnai (B)
Department of Applied Chemistry, Graduate School of Engineering, Osaka University,
Yamadaoka 2-1, Suita, Osaka 565-0871, Japan
e-mail: tohnai@chem.eng.osaka-u.ac.jp
© Springer Nature Singapore Pte Ltd. 2020
M. Sakamoto and H. Uekusa (eds.), Advances in Organic Crystal Chemistry,
https://doi.org/10.1007/978-981-15-5085-0_10
185