Exploiting Hansen solubility parameters to tune porosity and function in conjugated microporous polymers

Abstract

Here we expand our recently reported Bristol–Xi'an Jiaotong (BXJ) approach using simple salts to fine-tune the porosity of conjugated microporous materials synthesized by various reaction approaches, including Buchwald–Hartwig (BH), Sonogashira–Hagihara, oxidative coupling and Suzuki cross-coupling. The surface area and the porosity of the produced conjugated microporous polyanilines (CMPAs) acquired from the non-salt-added BH coupling are optimized by the addition of inorganic salts. BXJ-salt addition provides a facile route to radically improve the BET surface area from 28 to 901 m² g⁻¹ for PTAPA and from 723 m² g⁻¹ to 1378 m² g⁻¹ for PAPA in a controllable manner. In addition, the surface area shows a gradual decrease with an increase in the ionic radius of salts. We furthermore show high compatibility of this approach in the synthesis of typical CMPs, further increasing the surface area from 886 to 1148 m² g⁻¹, 981 to 1263 m² g⁻¹, and 35 to 215 m² g⁻¹ for CMP-1, PTCT and p-PPF, respectively. More importantly, the BXJ approach also allows the broad PSD of the CMPs to be narrowed to the microporous range only, mimicking COFs and MOFs. With the porosity optimized, CO₂ uptakes are dramatically improved by >300% from 0.75 mmol g⁻¹ to 2.59 mmol g⁻¹ for PTAPA and from 2.41 mmol g⁻¹ to 2.93 mmol g⁻¹ for PAPA. Careful addressing of Hansen solubility parameters (HSPs) of solvents and resulting polymers through salt addition has the potential to become an important design tool for the preparation of fully tuneable porous materials. We are currently exploring further methods to tune both structure and function in a wide range of organic porous materials.