Free‐Standing Janus Nanosheets: Ultrafast Self‐Assembly and Versatile Biphase‐Application

Abstract The development of stable Janus architectures suitable for biphasic applications holds significant importance. A novel approach is introduced for interfacial supramolecular self‐assembly, resulting in 2D Janus nanosheets (OA‐TA/Fe) exhibiting an amphiphilic nature. These nanosheets consist of hydrophilic coordination complexes of ferric ions (Fe 3+ ) and tannic acid (TA) on one side of both surfaces and hydrophobic alkyl chains on the other side of both surfaces. The synthesis of these 2D Janus nanosheets involves a simple, ultrafast, and environmentally benign process, eliminating the need for time‐consuming multistep procedures and harsh synthetic conditions typically associated with Janus architecture formation. By exploiting the inherent singular anisotropic wettability inherent in OA‐TA/Fe‐2, the efficacy of these innovative Janus nanosheets in the efficient separation of various organic liquid‐in‐water and water‐in‐organic liquid emulsions is elucidated. Subsequent post‐modification of OA‐TA/Fe has facilitated the highly efficient remediation of contaminated oily wastewater, serving as a model biphasic catalysis reaction, wherein the Janus nanosheets function simultaneously as emulsifiers and catalysts within biphasic mixtures. The methodology establishes a rapid self‐assembly approach for the creation of amphiphilic free‐standing Janus nanosheets, offering compelling prospects for their application in diverse fields, as exemplified by, but not limited to, the case studies presented herein.