Interfacial Constraints Guided by Micro‐Nano Bubbles Spatial Templates to Regulate Polyamide Membrane Structure and Property

Abstract Conventional interfacial polymerization (IP) methods typically affect the diffusion behavior of amine monomers throughout the aqueous phase, making it difficult to finely control the IP rate‐determining step. In this study, the interfacially adsorbed H 2 micro‐ or nanobubbles are employed as spatial templates to effectively regulate the diffusion paths and rates of amine monomers on the organic phase side through the free‐IP process. Nanobubbles are employed to construct polyamide layers enriched with nanovoids. In contrast, microbubbles, facilitated by interfacial gas transport, eliminated in situ‐generated bubbles during the IP and promoted the formation of ultrathin polyamide layers. The interfacial confinement effect of microbubbles is independent of gas properties (H 2 , CO 2 , and O 2 ), and the method applies to the design of ultrathin nanofiltration membranes. When tested in 2000 ppm NaCl brackish water, ultrathin reverse osmosis membranes exhibited exceptional performance, with the water permeance of 4.53−5.15 L·m −2 ·h −1 ·bar −1 and the salt rejection of over 98.2%. The permselectivity of these ultrathin membranes approached the upper bound for thin‐film composite (TFC) membranes in free‐IP. This work emphasizes the importance of interfacial constraints, interfacial adsorption, and interfacial gas transport in the IP process, thereby redefining the role of bubbles in the preparation of TFC membranes.