Engineering nanocomposite metal-phenolic network membranes with hollow MOFs via in-situ etching for High-efficiency organic solvent nanofiltration

Organic solvent nanofiltration (OSN), as an emerging membrane separation technology, holds great potential in pharmaceutical and chemical applications. However, the development of such a promising technology is severely retarded by the trade-off between permeability and selectivity. Herein, we report a novel thin-film nano composite (TFN) membrane by incorporating hollow metal-organic frameworks (MOFs) into the metal-phenolic network (MPN) selective layer for highly efficient OSN. This nanocomposite selective layer is fabricated via an aqueous deposition of tannic acid (TA) and Fe-II ions with MOFs, during which the MOFs are in-situ etched to a hollow structure. Attributed to the extra transfer channels provided by hollow MOFs, the methanol permeance of the TFN membranes increases to 24.7 Lm(-2) h(-1) bar(-1), exhibiting an improvement of 270% compared with the membranes without MOFs (9.1 Lm(-2)h(-1)bar(-1)). Meanwhile, the coordination interaction between TA and metal centers in MOFs endows excellent interfacial compatibility between MPN matrix and MOF fillers, guaranteeing a defect-free selective layer and thus high rejection for small organic molecules (> 99% for Alcian blue). Furthermore, various MOFs, including ZIF-67, prussian blue (PB), and MIL-53(Al), are also employed to fabricate MPN/MOF nanocomposite membranes, proving the availability and universality of this facial aqueous deposition strategy. Additionally, we also take deep insight into the mechanism of in-situ etching based on the density functional theory (DFT) calculation to pave the way for the fabrication of TFN membranes with other hollow nanofillers. This work provides a sufficient strategy for the design and construction of novel highly efficient OSN nanocomposite membranes with excellent permeability and retention performance.