Performance of pentaethylenehexamine modified MIL-101(Cr) metal-organic framework in CO₂ adsorption

The metal-organic framework MIL-101(Cr) was synthesized via hydrothermal process and then modified with pentaethylenehexamine (PEHA) through refluxing in ethanol. Various measures such as SEM, XRD, N₂ sorption, Elemental analysis and FT-IR were used to characterize the structure, morphology and properties of PEHA-grafted MIL-101(Cr). Meanwhile, the performance of PEHA-grafted MIL-101(Cr) in CO₂ adsorption was investigated under 25℃. The results illustrate that the loading of PEHA in MIL-101(Cr) can conspicuously enhance the CO₂ adsorption capacity. PEHA-grafted MIL-101(Cr) with a PEHA loading of 0.24 mL exhibits the highest capacity for CO₂ adsorption; the adsorption capacity reaches 58.944 mg/g at 25℃ and atmospheric pressure, which is 33% higher than that of the unmodified MIL-101(Cr) (44.208 mg/g). In addition, the CO₂ adsorption capacities on both MIL-101(Cr) and PEHA-MIL-101(Cr) are greatly enhanced by increasing pressure, reaching 1 147.59 and 1 256.74 mg/g at 1.1 MPa, respectively. These results suggest that PEHA-modified MIL-101(Cr) could be a good candidate adsorbent for CO₂ capture at high pressure.