Macrocyclic polyamines mediated in situ growth of MOFs for the high permeance of nanofiltration membranes

Abstract

Incorporation of nanosized metal organic frameworks (MOFs) fillers into polyamide layer can essentially enhance the performance of thin film nanocomposite (TFN). However, in situ growth of MOFs during interfacial polymerization (IP) is impeded by the insolubility of metal precursors in alkaline aqueous solutions. Herein, 1,4,7,10-tetraazacyclododecane (Cyclen), a macrocyclic polyamine capable of complexing metal ions, was integrated into the IP process to fabricate TFN membranes with in situ synthesized zeolitic imidazolate framework-8 (ZIF-8). Compared to the conventional piperazine-trimesoyl chloride (PIP-TMC) membrane, the modified PIP + Cyclen-TMC membrane features a thinner and denser polyamide layer. After the incorporation of ZIF-8, the polyamide layer becomes looser, more hydrophilic and electronegative. The resultant TFN membranes demonstrated exceptional water permeance (31.4 L m−2 h−1 bar−1) and improved selectivity (96.3 %), signifying a permeance enhancement of 182.6 % compared with that of the pristine PIP-TMC membrane. Additionally, the optimized membrane manifested enhanced fouling resistance and long-term stability. This macrocyclic polyamines mediated in situ growth technique can be extended to other combinations of macrocyclic polyamines and metal precursors, offering a novel paradigm for the fabrication of TFN-MOFs membranes for desalination.