Adsorptive removal of uremic toxins using Zr-based MOFs for potential hemodialysis membranes

Protein-bound uremic toxins (PBUTs) are difficult to remove through dialytic procedures, and the accumulation of PBUTs is always associated with adverse symptoms in end-stage kidney disease. Hemoperfusions and novel membranes have been developed for the removal of PBUTs, but still suffer from low efficiency. Herein, we investigated the adsorption performance of three zirconium metal–organic frameworks (Zr-MOFs: UiO-66, UiO-66-SO₃H, and UiO-66-(COOH)₂) for two typical PBUTs (indoxyl sulfate, IS; hippuric acid, HA). We found that Zr-MOFs could adsorb PBUTs efficiently with a capacity of as high as 49.5 mg g⁻¹ for IS and 38.3 mg g⁻¹ for HA, respectively, due to the van der Waals interactions, Coulomb interactions, and π–π interactions. Density functional theory simulations demonstrated that H-bonding on basis of the –SO₃H and –COOH groups could endow MOFs with better absorptivity. Further, to expand to practical hemodialysis applications, we incorporated Zr-MOFs into a polylactide (PLA) matrix to fabricate MOFs-based mixed matrix membranes (MMMs). The MMMs showed excellent in vitro biocompatibility and high water flux up to 260 L m⁻² h⁻¹. Under static conditions, the MMMs could remove HA and IS with a percentage of 75 and 78% in 4 h, respectively, whereas PLA membrane removed 12% of HA and 13% of IS. Under dynamic conditions, MMMs could remove 57% of IS and 54% of HA in 30 min; by contrast, PLA membrane only removed 2.9% of IS and 2.2% of HA. These MOFs-based MMMs with exceptional absorptivity, high water flux, and good biocompatibility might show great prospects in the foreground for the application of safe and efficient blood purification.