Superhigh and reversible NH3 uptake of cobaltous thiocyanate functionalized porous poly ionic liquids through competitive and cooperative interactions

Abstract

In this work, porous PIL-TAs were reported for superhigh capacity and reversible NH3 uptake, where PIL-TAs are cobaltous thiocyanate (Co(II)(SCN)42-, TA) functionalized poly ionic liquids (PILs). Due to the structural support of TA as well as the interactions between TA and imidazolium cation, the PIL-TAs possess porous structure and optimized properties. Superhigh NH3 uptake capacity of 13.2–20.1 mmol g−1 at STP of PIL-TAs was achieved, which is higher than most of the reported sorbents. In detail, the cooperative interactions including the NH3 coordinating with Co(II) instead of SCN- and hydrogen bonding of C2H in imidazolium (C2H…NH3) benefit to high capacity of NH3 uptake. Reversely, the NH3 release would be directed by the competition of the free SCN- with NH3 to reform PIL-TAs. The competitive interaction with SCN- promotes NH3 release by temperature and pressure swinging, which contributes the adsorbents recyclable. The cooperative and competitive interactions make these PIL-TAs possess high gas capacity and feasible desorption, which might be a potential strategy for designing novel gas sorbents.