Immobilization of a Polar Sulfone Moiety onto the Pore Surface of a Humid-Stable MOF for Highly Efficient CO Separation under Dry and Wet Environments through Direct CO-Sulfone Interactions.

The stability of microporous metal-organic frameworks (MOFs) in moist environments must be taken into consideration for their practical implementations, which has been largely ignored thus far. Herein, we synthesized a new moisture-stable Zn-MOF, , , by utilizing a bent organic linker 4,4'-sulfonyldibenzoic acid (HSDB) containing a polar sulfone group (-SO) and a N, N-donor spacer () with a Brunauer-Emmett-Teller surface area of 216 m g. This material displays greater CO adsorption capacity over N and CH with high IAST selectivity, which is also validated by breakthrough experiments with longer breakthrough times for CO. Most importantly, the separation performance is largely unaffected in the presence of moisture of simulated flue gas stream. Temperature-programmed desorption (TPD) analysis shows the ease of the regeneration process, and the performance was verified for multiple cycles. In order to understand the structure-function relationship at the atomistic level, grand canonical Monte Carlo (GCMC) calculation was performed, indicating that the primary binding site for CO is between the sulfone moieties in . CO is attracted to the bonded structure (V-shape) of the sulfone moieties in a perpendicular fashion, where C is aligned with S, and the CO axis bisects the SO axis. Thus, the strategic approach to immobilize the polar sulfone moiety with a high number of inherent stronger M-N coordination and the absence of coordination unsaturation made this MOF potential toward practical CO separation applications.