Metal-organic composite membrane with sub-2 nm pores fabricated via interfacial coordination

• Published in: Journal of membrane science 2019-10, Vol.587, p.117146, Article 117146
• Main Authors: Shen, Yu-Jie, Fang, Li-Feng, Yan, Yan, Yuan, Jia-Jia, Gan, Zhi-Qiang, Wei, Xiu-Zhen, Zhu, Bao-Ku
• Format: Article
• Language: English
• Subjects: Interfacial coordination; Metal-organic composite; Sub-2 nm; Tris-complex
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2019.05.070

A metal-organic composite membrane with sub-2 nm pores was developed via interfacial coordination reaction in biphasic systems for the first time. Herein, tannic acid (TA) was dissolved in water, as aqueous phase; iron(III) acetylacetonate (Fe(acac)3), used as Fe(III) source, was dissolved in n-hexane as organic phase. A detailed study was conducted to obtain the defect-free TA-Fe(III) separation layer, including the salt concentration in aqueous solution, pH of the aqueous solution and the ratio of TA to Fe(acac)3. The results indicated that the defect-free TA-Fe(III) composite membrane formed when the tris-complex (TA3-Fe(III)) was achieved. The optimal condition for preparing TA-Fe(III) composite membrane was using aqueous solution containing 0.4 M NaCl at pH = 6 with the ratio of TA to Fe(acac)3 of 10. Different from the typical separation layer formed on the membrane surface by interfacial polymerization, the TA-Fe(III) separation layer was formed in the pores of the substrate, which is attributed to the higher diffusion coefficient of Fe(acac)3 from organic phase to aqueous phase. This work provided a novel strategy to fabricate metal-organic composite membrane with sub-2 nm pores; meanwhile, the new-prepared membrane shows a high Na2SO4 rejection of 97.3% with the water permeance of 8.6 L m−2 h−1 bar−1, and a high VB12 rejection of 97.6%, indicating an excellent ion/molecule separation performance. [Display omitted] •TA-Fe(III) composite membrane with sub-2 nm pores was fabricated via interfacial coordination reaction for the first time.•Defect-free TA-Fe(III) composite membrane formed when the tris-complex (TA3-Fe(III)) was achieved.•Separation layer is formed in the pores of the substrate.•The membrane exhibited 8.6 L m−2 h−1 bar−1 of water permeance and 97.3% of Na2SO4 rejection.