Tuning the anion for ultrahigh and selective adsorption of low-concentration SO2 by functionalized ionic porous organic polymers

The efficient adsorption of low-concentration sulfur dioxide (SO2) is challenging and critical for our society, but the weak interaction between traditional porous materials and gas molecules limits their practical applications. In this work, a series of functionalized ionic porous organic polymers (IPOPs) with high content of active sites are designed and applied for efficient and selective adsorption of low-concentration SO2. By facile ion exchange methods, IPOPs can be successfully functionalized and the influence on BET surface area is relatively small compared with other reported functionalization methods. Meanwhile, the adsorption capacity of SO2 on functionalized IPOPs improved greatly, where an ideal IPOPs TBM-BIm4 contributes a record high adsorption capacity (9.23 mmol g-1) under reduced pressure of 0.1 bar, high SO2/CO2 selectivity as well as excellent reversibility. Through a combination of experimental adsorption, DFT calculation and spectroscopic investigation, such a ultrahigh capacity originated from multi-site adsorption of the functionalized anion of TBM-BIm4. The present work demonstrates that it is an effective strategy to design IPOPs by introducing specific functionalized anions for excellent performance in low concentration of gas.