Probing the origin and stability of bivalency in copper based porous coordination network and its application for H2S gas capture
Nishesh Kumar Gupta, Eun Ji Kim, Jiyeol Bae, Kwang Soo Kim
Abstract
Abstract A bivalent Cu(I,II) metal–organic framework (MOF) based on the 4,4′,4″-s-Triazine-2,4,6-triyl-tribenzoate linker was synthesized via a solvothermal method. The MOF possessed 43.8% of the Cu sites as Cu + with a surface area of 1257 m 2 g −1 . The detailed spectroscopic analysis confirmed dimethylformamide (DMF) solvent as the reductant responsible for Cu + sites in the synthesized MOF. The Cu + sites were easily accessible and prone to oxidation in hot water or acidic gas environment. The MOF showed water-induced structural change, which could be partially recovered after soaking in DMF solvent. The synthesized MOF showed a high hydrogen sulfide (H 2 S) uptake capacity of 4.3 mmol g –1 at 298 K and an extremely low H 2 S pressure of 0.0005 bar. The adsorption capacity was the highest among Cu-based MOFs with PCN-6-M being regenerable, which made it useful for deep desulfurization applications. The adsorbed H 2 S was mineralized to sulfide, sulfur, and sulfates, mediated by the Cu + /Cu 2+ redox cycle in the presence of adsorbed water and molecular oxygen. Thus, the study confirmed that DMF as a reductant is responsible for the origin of bivalency in PCN-6-M and possibly in other Cu-based MOFs reported in the literature. Also, the developed MOF could be a potential candidate for flue gas desulfurization and gas purification applications.