Facile and high-yield synthesis of improved MIL-101(Cr) metal-organic framework with exceptional CO₂ and H₂S uptake; the impact of excess ligand-cluster

The goal of this research was to investigate the effect of various cluster/ligand (X) and cluster/modulator (Y) ratios on the textural properties, reaction yield and gas uptake of MIL-101@M-X-Y. The results revealed that the surface area and pore volume of the [email protected] series (synthesized with Cr: H₂BDC of 1:2 instead of conventional 1:1) fascinatingly improved and reached 3596 m²/g and 1.65 cm³/g in [email protected] case, 23.8% and 27.9% higher than the conventional MIL-101(Cr) sample. Next, the CO₂ and H₂S adsorption isotherms of all synthesized materials were measured using an in-house made setup at 298 K and 1–35 bar. The [email protected] possessed high adsorption capacity for both CO₂ (3.16 mmol/g) and H₂S (7.63 mmol/g) at 1 bar, elevated up to 44.9% and 59.3% compared to the conventional MIL-101(Cr). This enhancement in the gas adsorption capacity, especially for polar H₂S molecules, was attributed not only to the superior textural properties of [email protected] but also to more created unsaturated Cr³⁺ sites providing stronger interactions at low pressures. Besides the eminent textural properties, gas uptake capacity and H₂S/CO₂ selectivity of the modified [email protected], its reaction yield reached as high as 71.9%, which was appreciably higher than 59.7% of the conventional MIL-101(Cr).