High-Performance Selective CO2 Capture on a Stable and Flexible Metal-Organic Framework via Discriminatory Gate-Opening Effect.

Abstract

Selective CO2 capture is of great significance for environmental protection and industrial demand. Here, we report a stable and flexible metal-organic framework (MOF) with excellent water/moisture stability, namely, ZnDatzBdc, that enables high-performance selective CO2 capture from N2 and CH4 via a discriminatory gate-opening effect. ZnDatzBdc shows reversible structural transformation between the open-phase (OP) state and the close-phase (CP) state, owing to the synergistic effect of breakage/re-formation of intraframework hydrogen bonds and the rotation of the phenyl rings. Significantly, ZnDatzBdc exhibits S-shaped isotherms toward CO2, resulting in a large CO2 theoretical working capacity of 94.9 cm3/cm3 under typical pressure vacuum swing adsorption (PVSA) operations, which outperforms other flexible MOFs showing the CO2 selective gate-opening effect except for the miosture-sensitive ELM-11. In addition, CO2 uptake of ZnDatzBdc is well maintained upon multiple water/moisture exposure, indicating its excellent stability. Moreover, ZnDatzBdc establishes remarkable CO2 selectivity with ultrahigh uptake ratios of CO2/N2 (107 at 273 K and 129 at 298 K) and CO2/CH4 (35 at 273 K and 44 at 298 K) at 100 kPa. The in situ gas sorption PXRD experiment verifies that the gate-opening effect takes place in the atmospheric environment of CO2 but not for N2 or CH4. Molecular simulation suggests the selective gate-opening of CO2 comes from its strong electrostatic interactions with the amino groups. Furthermore, effective breakthrough performance and easy regeneration are further confirmed. Hence, combined with excellent separation performance and remarkable stability, ZnDatzBdc can serve as a potential industrial adsorbent for selective CO2 capture.