Simultaneous use of MOFs MIL-101(Cr) and ZIF-11 in thin film nanocomposite membranes for organic solvent nanofiltration

Abstract

The MOFs Cr carboxylate MIL-101(Cr) and Zn imidazolate ZIF-11 have different chemical and textural properties. These properties have been combined to prepare thin film nanocomposite (TFN) membranes for organic solvent nanofiltration (OSN) with the two MOFs simultaneously embedded in the same membrane. The TFN membrane containing only ZIF-11 permeated faster than that with only MIL-101(Cr) when filtering sunset yellow (SY) (4.9 L m⁻² h⁻¹ bar⁻¹) and acridine orange (AO) (3.2 L m⁻² h⁻¹ bar⁻¹), although MIL-101(Cr) alone gave rise in both cases to better rejections (above 90%). The combination of the two MOFs led to a versatile TFN membrane that showed an intermediate performance that improved the rejections given by the TFN membrane synthesized with ZIF-11 and the permeances corresponding to the TFN membrane synthesized with MIL-101(Cr). The effect of the temperature on the TFN membranes designed for this work has also been studied, obtaining apparent activation energies of 13.2 ± 2.1 and 8.3 ± 1.1 kJ mol⁻¹ for the OSN of pure methanol and SY-methanol, respectively.