One-pot synthesis of MIL-101-NH₂(Cr) derivatives using GdmCl as a mediator for enhanced low CO₂ concentration capture

The development of metal–organic frameworks for carbon dioxide (CO₂) capture has drawn considerable interest among researchers with MIL-101(Cr) gaining significance owing to its high stability. This paper investigates the one-step synthesis of MIL-101-NH₂(Cr) by using guanidine hydrochloride as a mediator under relatively mild conditions (aqueous phase, reaction temperature of 120 °C, and without the use of mineralization agents such as hydrofluoric acid). MIL-101-NH₂(Cr) not only exhibited a high specific surface area with a Lewis-base site-rich ligand but also possessed a good CO₂ adsorption capacity of 3.96 mmol/g at 1 bar. Furthermore, diethylenetriamine (DETA) was loaded into MIL-101-NH₂(Cr) to design a new CO₂ adsorbent DETA@MIL-101-NH₂(Cr). The loaded material maintained the original structure and also displayed an improved adsorption capacity of 0.29 mmol/g under low (< 0.11 bar) CO₂ partial pressure. The absorbents possessed good selectivity, stability, and recyclability which make them ideal candidates for CO₂ capture.