Preparation of HKUST-1/PEI mixed-matrix membranes: Adsorption-diffusion coupling control of small gas molecules

Abstract

HKUST-1 nanocrystals (50–80 nm) were homogeneously dispersed in a polyetherimide (PEI) polymer matrix. The use of a capping agent (sodium formate) prevented the agglomeration of HKUST-1 nanocrystals in the casting solution. The highly dispersed HKUST-1 nanocrystals were found to strengthen the interactions with the PEI and minimize the interfacial holes by providing more accessible Cu unsaturated metal sites for the CO bonds on the five-membered rings of the PEI matrix. The PEI membrane loaded with 30 wt % HKUST-1 nanocrystals (30-N-HKUST-1/PEI) showed a high H2 permeability (193.3 Barrer at 25 °C under 1.5 bar) and good ideal H2/CH4 and H2/CO2 selectivity factor of 101.7 and 20.6 in a single gas test, respectively. In the gas mixture test, it also showed a good separation performance, i.e., a H2/CH4 and H2/CO2 selectivity factor of 82.4 and 16.5 was measured, respectively. The 30-N-HKUST/PEI membrane was tested in a gas mixture at different temperatures (25–100 °C), different pressures (0–3 bar) and various time (5–72 h) to study the performance in more realistic conditions thus to be further considered in the separation of syngas.