Defect-Engineering of Anionic Porous Aromatic Frameworks for Ammonia Capture

Defects in many types of porous materials have been demonstrated for controlling the pore size distribution and specific surface area as well as manipulating chemical functionality, which strongly affects their mass-transport pathways and gas adsorption behaviors. Here, unraveled structural evidence for the presence of defects in porous ionic polymers (PIPs) with weakly coordinating anions is presented. We present the concise synthesis of a tetraphenylborate-based anionic porous framework, which allows for the construction of PIPs with tricoordinated boron vacancies via a defect-engineering strategy. The resultant PIP-X possesses a high surface area of 935 m(2) g(-1) and displays excellent chemical stability in water and organic solvents. Importantly, the controllable vacancies and porosity of polymers were investigated using the solid-state nuclear magnetic technique. The prepared polymer (Cu@PIP-X) has multiple active sites that contain charged skeletons, Lewis acid defects, and metal ions and thus exhibits improved ammonia (NH3) adsorption performance compared with a neutral polymer (PAF-1) and a defect-free polymer (PIP-H). Notably, the strong interactions between the gas molecules and the PIP-X are reversible with simple heating to 100 degrees C and display outstanding recyclable ability without structure collapse. This work thereby provides a perspective to develop defective anionic polymers as a versatile type of ion-exchange material for gas uptake.

Automated summary

This study demonstrates how defects can be introduced into porous ionic polymers using a defect-engineering strategy, allowing for control of pore size distribution, specific surface area, chemical stability, and gas adsorption performance. The presence of controllable vacancies and porosity in polymers was investigated using solid-state nuclear magnetic technique, showing improved ammonia adsorption performance compared to neutral and defect-free polymers. The strong interactions between gas molecules and the PIP-X are reversible, displaying outstanding recyclable ability without structure collapse, making defective anionic polymers a versatile type of ion-exchange material for gas uptake.