Porous Organic Salts Composed of Terphenyl Sulfonic Acid and Their Bottleneck Designability

Abstract

Porous organic salts (POSs) are constructed through a strong charge‐assisted hydrogen bond between sulfonic and amino groups. The molecular design of sulfonic acid, the linker part, enables various porous structures. In the current work, we synthesized p‐terphenyl‐4,4’’‐disulfonic acid (TPDS), whose molecular structure can be easily modified by organic synthesis. Combining of TPDS and bulky tri‐p‐tolylmethanamine (TPMA‐Me), which has three methyl groups at each para‐position of the phenyl groups of triphenylmethylamine (TPMA), gave POS with one‐dimensional pore channels having two different types of bottlenecks. The central benzene ring of TPDS is exposed on the surface of the pore. Therefore, we combined 4,4′‐(benzo[c][1,2,5]thiadiazole‐4,7‐diyl)dibenzenesulfonic acid (BTDBS) containing 2,1,3‐benzothiadiazole (BT) with TPMA‐Me, and successfully constructed a one‐dimensional pore channel with a bottleneck of 3.5 Å, by exposing BT to the surface of the pore. BTDBS/TPMA‐Me exhibited a large adsorption/desorption hysteresis of nitrogen because of the bottleneck, electronic state of BT, and larger oxygen adsorption than the isostructural TPDS/TPMA‐Me. Systematic and intended modulation of the pore structure of POS based on the modification of sulfonic acid was demonstrated, and for the first time, we established a precise design methodology for a one‐dimensional pore channel with a bottleneck and high crystallinity in metal‐free porous organic materials.

Crystalline porous organic salts

“…Regrettably, these networks experienced structural collapse upon removing the guest molecules, thus lacking permanent porosity. Additionally, Tohnai et al employed organic sulfonic acids and organic amines to successfully construct stable supramolecular clusters 62 through ionic bonding, and construct many salts 63–68 based on the supramolecular clusters. These early investigations significantly advanced the development and evolution of CPOSs.…”