Tuning Pore Chemistry in Dioxin-Linked Porous Organic Polymers for Enhanced High-Pressure CO2 Uptake

Abstract

Precise tuning of pore chemistry in three-dimensional porous organic polymers (3D-POPs) is critical for high-performance gas (CO<inf>2</inf>)-separation. Here, we demonstrate the impact of functional groups on the dioxin-linked 3D-tPOPs bearing a tetraphenylene core, synthesized under solvothermal conditions using NaCl as a template, on the low- and high-pressure CO<inf>2</inf> uptake. The post-synthetic amidoxime functionalization of 3D-tPOPs, involving the reaction of pendant nitrile moieties with hydroxylamine hydrochloride, has been shown to precisely tailor pore chemistry without altering the network structure. Whereas the incorporation of the amidoxime moieties, 3D-tPOP-AO, enables higher heteroatom content, a critical factor to enhance CO<inf>2</inf> affinity at low pressures, strong hydrogen bonding interactions between amidoxime units limit framework flexibility, thus leading to a significant decrease in the high-pressure gas uptake. 3D-tPOPs on the other hand showed a high CO<inf>2</inf> uptake capacity of 57.4 wt% at 33 bar and 270 K; after modification, CO<inf>2</inf> uptake capacity decreased to 19.4 wt% at 273 K and 34 bar. Similarly, CH<inf>4</inf> uptake capacity also decreased from 14.0 wt% at 116 bar and 270 K to 3.8 wt% at 75 bar and 273 K. These findings highlight the critical role of the interactions between functional groups and pore chemistry to form robust adsorbents with high CO<inf>2</inf> uptake performance at high pressures. © 2025 The Author(s). Helvetica Chimica Acta published by Wiley-VHCA AG.