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

© 2018 Elsevier Inc. 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 MIL-101@M-0.5-Y 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 MIL-101@M-0.5-0.5 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 MIL-101@M-0.5-0.5 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 MIL-101@M-0.5-0.5 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 MIL-101@M-0.5-0.5, its reaction yield reached as high as 71.9%, which was appreciably higher than 59.7% of the conventional MIL-101(Cr).