Trace SO2 Gas Capture in Stable 3D Viologen Ionic Porous Organic Framework Microsphere.

Eliminating trace sulfur dioxide (SO2) using nanoporous adsorbents is industrially preferred yet of great challenge due to the competitive adsorption of CO2. Herein, we reported a highly stable 3D viologen porous organic framework (Viologen-POF) microsphere via one pot polymerization reaction of 4,4'-bipyridine and tetrakis(4-(bromomethyl)phenyl)methane. Compared to the previously reported irregular POF particles, viologen-POF microsphere shows better mass transfer uniformity. Owing to the intrinsic separated positive and negative electric charges center in viologen-POF microspheres, it exhibits excellent SO2 selective capture performance, which can be collaboratively confirmed by static single-component gas adsorption, time-dependent adsorption rate, and multicomponent dynamic breakthrough experiments. Viologen-POF exhibits high SO2 absorption capacity (1.45 mmol g-1) at ultralow pressure of 0.002 bar and high SO2/CO2 selectivity of 467 at 298 K and 100 kPa (SO2/CO2, 10/90, v/v). The theoretical calculations based on density functional theory (DFT) and DMol3 modules in Material Studio (MS) were also performed to elucidate the adsorption mechanism of viologen-POF toward SO2 at the molecular level. This study represents a new type of viologen porous framework microsphere for trace SO2 capture, which will pave the way on the applications of ionic POF for toxic gas adsorption and separation.