Tuning adsorption selectivity of H2S and CO2 with robust bimetallic metal-organic frameworks

Mitigating global warming by carbon capture and storage is enshrined as the most prominent technology for environmental CO 2 emissions. However, separating impurities, such as H 2 S, in the captured CO 2 remains a challenge that incurs higher industrial processing costs. In this work, four metal-organic frameworks (MOFs) materials, UiO-66(Zr), MIL-68(In), MIL-101(Cr) and HKUST-1, were investigated for selective adsorption of H 2 S through breakthrough experiments. Bimetallic UiO-66(Zr/M) and MIL-101(Cr/M) (where M is Fe and Cu) were constructed by post-synthetic modification approach. Notably, the UiO-66(Zr/Cu) demonstrated an ultra-high separation of H 2 S over CO 2 , recording selectivity value of 50. Further analysis confirmed that H 2 S complex with hydroxyl groups on UiO-66(Zr/Cu) and then converted to elemental sulfur and sulfate by Cu(II) which is first reduced to Cu(I) and then oxidized back to Cu(II) in the presence of O 2 , completing the Cu redox cycle. Hence, the rational design of bimetallic framework materials is a promising technique for selective separation of H 2 S and CO 2 . • Engineering the metal nodes of MOFs to optimize gas selective capture • Post-synthetic modification to construct bimetallic UiO-66(Zr/M) and MIL-101(Cr/M) • The selective H 2 S/CO 2 adsorption of UiO-66(Zr/Cu) outperformed other MOFs • The captured H 2 S on UiO-66(Zr/Cu) were converted to elemental sulfur and sulfate • In the Cu redox cycle H 2 S reduces Cu(II) to Cu(I) which is oxidized to Cu(II) by O 2