Surface Engineering of Zr BDC Nanoparticles via Conjugation with Lysine to Enhance the CO₂/N₂ Separation Performance of Chitosan Mixed Matrix Membranes under Dry and Humid Conditions

Abstract

Mixed matrix membranes (MMMs) incorporated with rigid porous metal−organic framework (MOF) nanoparticles (NPs) are well known for their increased carbon dioxide (CO 2 ) separation performance. For successful separation of CO 2 from the flue gas, CO 2 -philic zirconium-based MOF NPs (Zr BDC or UIO-66) were synthesized and decorated with L-lysine amino acids to incorporate into a chitosan (CS) polymer matrix. The high porosity and surface area of the MOF NPs aided in the CO 2 separation permeance, while the selectivity was addressed by the amine functional groups present in L-lysine. The covalently bonded L-lysine onto Zr BDC NPs has a greater CO 2 affinity due to the dangling amine groups. Additionally, the amine conjugation strengthened the hydrogen bonds between the MOF and the CS matrix, thereby improving the dispersibility of MOF in the polymer matrix. After successful characterization studies, it was discovered that fabricated MMMs with a 7 wt % loading of lysineconjugated Zr BDC (lys-c-Zr BDC) NPs with a 4 μm active layer thickness demonstrated better results than the pristine CS and the Zr BDC-embedded CS MMM. The composite lys-c-Zr BDC incorporated CS MMM showed a CO 2 permeance of 34.9 GPU and a steady CO 2 /N 2 separation factor of 29.4 under dry conditions and a CO 2 permeance of 135.2 GPU and a steady CO 2 /N 2 separation factor of 71.5 under swollen conditions at 85 °C and 0.221 MPa feed pressure. It has also been shown that, under optimum conditions, the fabricated membrane has successfully surpassed the Robeson upper bound curve, which makes it suitable for commercial applications.

Green-Synthesized HF-free MIL-100(Fe) Nanoparticle-Infused Chitosan Mixed-Matrix Membranes for Enhanced CO2 Permeance

“…Therefore, nanosize of the MOF material adds on to its intrinsic properties toward the enhanced CO 2 capture activity. In this regard, a variety of MOFs were developed to utilize as nanofiller for MMMs, such as Cu-BPY-HFS, HKUST-1, ZIF-8, UiO-66, , Mil-53, MIL-100, including MIL-100­(Fe, Al, Cr, Ni, etc. ). − MIL-100­(Fe) is one of the few thermodynamically stable MOFs with high surface area and strong adsorption separation properties especially at humid conditions .…”