Ultrathin Films of Organic Networks as Nanofiltration Membranes via Solution-Based Molecular Layer Deposition

Abstract

Ultrathin films of organic networks on various substrates were fabricated through the solution-based molecular layer deposition (MLD) technique. The rigid tetrahedral geometries of polyfunctional amine and acyl chloride involved in the reaction ensure the continuity of the polymerization process. A linear increase in film thickness with respect to cycle number was observed by UV-vis adsorption, ellipsometry, and quartz crystal microbalance. The growth rate per MLD cycle is 1.6 nm, which can be controlled at the single molecular level. For the first time, we develop the MLD method on the top of hydrolyzed PAN substrate, resulting in nanofiltration (NF) membranes. The stepwise growth was monitored via attenuated total reflectance infrared studies. The separation performance of the obtained membrane for various solutes was sensitive to the terminated layers and number of cycles. The rejection of NH(2)-terminated membranes follows the order of CaCl(2) > Na(2)SO(4) > NaCl, while the order for COOH-capped surface is Na(2)SO(4) > CaCl(2) > NaCl. The absolute value of zeta potential for the MLD membranes decreases with the addition of deposition layers. The moderate water flux for the resulting membrane is due to the reduced porosity of the support as well as the low roughness and hydrophilicity of the membrane surface. This bottom-up process provides a promising approach for construction of long-term steady NF membranes with nanoscale dimensions.

Functionalized Porous Aromatic Frameworks as High‐Performance Adsorbents for the Rapid Removal of Boric Acid from Water

“…Materials : Tetrakis(4‐bromophenyl)methane was synthesized according to a previously reported procedure . All other starting materials and reagents were purchased from Sigma–Aldrich and used as received, unless otherwise stated.…”

Layer-by-layer (LBL) assembly technology as promising strategy for tailoring pressure-driven desalination membranes

“…For instance, Qian et al deposited a tetrafunctional amine and a tetrafunctional acid chloride sequentially on a microporous UF support to synthesize a novel polyamide membrane. [58] The membrane showed a high multivalent ions rejection. However, this type of membrane endured a relatively low monovalent ions removal (46%).…”

Nanofiltration membranes with dually charged composite layer exhibiting super-high multivalent-salt rejection

“…Previous studies have demonstrated that the dramatic change of rejection order always attributes to the reversal of membrane charge property [45,46]. The separation performance change after TMC treated can be explained as follows.…”