Defect-Healed Carbon Nanomembranes for Enhanced Salt Separation: Scalable Synthesis and Performance

Ultrathin carbon nanomembranes (CNMs), fabricated from crosslinking self-assemblies of molecular precursors, are 2D membranes that possess well-defined physical and chemical properties.¹ Featuring a high density of sub-nanometer channels, CNMs enable superior salt separation performance compared to conventional membranes.² However, defect occurrence during synthesis and transfer processes impedes their technical realization on a macroscopic scale.<br/>Here, we introduce a practical and scalable interfacial polymerization method to effectively heal defects while preserving the sub-nanometer pores within CNMs. Defects in CNM composites were successfully repaired by interfacial polymerization of polyamide using m-phenylenediamine as the aqueous phase monomer and trimesoyl chloride as the oil phase monomer. The defect-healed CNMs exhibit exceptional performance in forward osmosis (FO), achieving a water flux of 105 L m⁻² h⁻¹ and a specific reverse salt flux as low as 0.1 g L⁻¹ when measured with 1M NaCl as draw solution. This water flux is ten times higher than commercially available FO membranes. Through successful implementation of the defect-healing method and support optimization, we demonstrate the scalable synthesis of fully functional, centimeter-scale CNM-based composite membranes, showing a water permeance comparable to commercial membranes and a salt rejection of ~99.8%. Our defect-healing method presents a promising pathway to overcome limitations in CNM synthesis, unlocking their potentials for practical salt separation applications.<br/><br/>(1) Turchanin, A.; Gölzhäuser, A. Carbon Nanomembranes. <i>Adv. Mater.</i> <b>2016</b>, <i>28</i> (29), 6075–6103. https://doi.org/10.1002/adma.201506058.<br/>(2) Yang, Y.; Hillmann, R.; Qi, Y.; Korzetz, R.; Biere, N.; Emmrich, D.; Westphal, M.; Büker, B.; Hütten, A.; Beyer, A.; Anselmetti, D.; Gölzhäuser, A. Ultrahigh Ionic Exclusion through Carbon Nanomembranes. <i>Adv. Mater.</i> <b>2020</b>, <i>32</i> (8), 1907850. https://doi.org/10.1002/adma.201907850.