L-Arginine-functionalized MIL-101: Structural optimization and enhanced greenhouse gas capture

To mitigate the greenhouse effect, this study employs a hydrothermal method to synthesize a series of MIL-101 materials modified by partial substitution of H₂BDC with L-arginine (MIL-101-X%Arg, where X = 0, 9, 11, 13, 15, 17, 19) and assesses their performance in greenhouse gas capture. BET characterization and single-gas adsorption experiments reveal that MIL-101-13 %Arg is the optimal sample, with a BET surface area of 2831 m²/g, significantly higher than MIL-101-0 %Arg (1269 m²/g). The adsorption capacities for CO₂, SF₆, C₂F₆, NF₃, CF₄, CH₄ and N₂ are enhanced by approximately 54 %, 76 %, 67 %, 48 %, 37 %, 60 % and 46 %, respectively, with adsorption behavior predominantly following a monolayer model. Pore size distribution, FTIR, PXRD, SEM and TG-DSC analyses indicate that monodentate L-arginine doping disrupts the bidentate symmetry of H₂BDC, introducing localized coordination defects and active functional groups, and causing slight distortions in the crystal framework. This results in micropore splitting, changes in pore size and increased asymmetry, even forming secondary pores. These structural modifications significantly optimize the pore structure, volume and surface chemistry, while enhancing crystal morphology and maintaining good thermal stability. MIL-101-13 %Arg demonstrates excellent separation performance in dynamic binary gas separation experiments, with selectivities for SF₆/N₂, CO₂/N₂, C₂F₆/N₂, NF₃/N₂, CF₄/N₂ and CH₄/N₂ of 32.38, 27.95, 25.95, 10.37, 7.47 and 4.77, respectively, all surpassing ideal selectivity at the same pressure. These findings confirm its significant potential for greenhouse gas capture and separation, offering a solid theoretical and experimental foundation for developing efficient, cost-effective materials to address global climate change.