Synergistic effect between tannic acid-Fe3+ and chitosan hydrogel-coated covalent organic framework: Endowing better nanofiltration performance and stability

The weak interfacial interaction of nanomaterials and substrate is an important factor affecting the stability and rejection of nanofiltration membranes. Herein, two materials of covalent organic framework modified by chitosan hydrogels (CH@COF) and tannic acid (TA)-Fe3+ served as an interlayer of the thin-film composite (TFC) membrane to overcome this problem. The synergistic effect between CH@COF and TA-Fe (such as constructing stable chemical bonds between the polyamide layer and substrate, increasing the degree of cross-linking of the polyamide layer, and decreasing its thickness) endows the TFC/TA-Fe(CH@COF) membrane with excellent nanofiltration performance and stability. Its water permeability was 16.17 L m−2 h−1 bar−1, which was 185% of that of the TFC-control membrane (8.74 L m−2 h−1 bar−1), and the rejections of the membrane for norfloxacin, ciprofloxacin, and ofloxacin were 94.89%, 99.07%, and 99.10%, respectively. In addition, its flux recovery rate (FRR) values for high-concentration sodium alginate and bovine serum albumin were 98.32% and 97.99%, respectively, indicating outstanding antifouling performance. This work emphasizes the synergy and potential of different materials as an interlayer in high-performance TFC membranes.