Polyethyleneimine NH2-UiO-66 nanofiller-based mixed matrix membranes for natural gas purification

Effective separation of CO 2 from CH 4 is crucial for the purification of natural gas, which requires membrane materials with high permeability, selectivity, and stability of under high pressures. In this work, a high CO 2 -affinity MOF-based nanofiller (P in @NH 2 -UiO-66) was prepared and integrated in polyetherimide (PEI) to prepare mixed matrix membranes (MMMs) for enhanced CO 2 /CH 4 separation capabilities. The P in @NH 2 -UiO-66 nanofiller comprised an in situ-formed polyethyleneimine-NH 2 -UiO-66 composite prepared via a one-pot synthesis. The polyethyleneimine was covalently attached to the H 2 BDC-NH 2 ligand allowing for a stronger integration within the PEI matrix. The polyethyleneimine affects the nucleation of MOF, leading to miniaturization of the MOF particles. The smaller-sized filler is beneficial for improved interaction at the filler-matrix interface. The numerous amino functionalities grafted onto the NH 2 -UiO-66 increased the CO 2 adsorption sites, thereby enhancing the affinity for CO 2 . Owing to the improved interaction, the elevated CO 2 attraction, and the inherent properties of the porous NH 2 -UiO-66, the fabricated MMMs preformed superior in separating CO 2 /CH 4 . The 30-P in @NH 2 -UiO-66-PEI membrane (containing 30 wt% nanofiller) exhibited a CO 2 /CH 4 selectivity of 27.7 and a CO 2 permeability of 2498.9 Barrer. The CO 2 permeability was 21 times greater than that of the pristine PEI membrane, and 4 times higher compared to P@NH 2 -UiO-66 MMM with polyethyleneimine modified MOF filler prepared by a traditional wet impregnation method. Additionally, the novel MMM demonstrates excellent separation stability under conditions that mimic industrial settings, demonstrating its potential application for natural gas purification.