Photothermal PCN-134-2D interlayer-driven foaming intensification for improving lithium enrichment in forward osmosis membranes

The increasing demand for lithium driven by the rapid growth of the new energy industry has highlighted the need for efficient lithium enrichment technologies. Forward osmosis (FO) membranes are considered suitable for lithium concentration because of their low energy consumption; however, conventional FO membranes suffer from low water permeability caused by the funnel effect and suboptimal separation layer structures. This study aims to enhance lithium enrichment performance by introducing photothermal porous coordination network (PCN-134-2D) nanosheet interlayers in membranes to regulate interfacial polymerization and promote structural optimization. PCN-134-2D nanosheets were deposited on the support layer and exposed to visible-light irradiation under varying light intensities during interfacial polymerization to increase the interface temperature. The increased temperature promoted gas release from the aqueous phase and induced in situ foaming, resulting in the formation of protruding structures in the separation layer. These structures increased surface roughness and internal nanovoids to mitigate the funnel effect. Moreover, the porphyrin-based PCN-134-2D nanosheets enhanced the interaction with m -phenylenediamine, facilitating the formation of a thin and dense polyamide layer. The resulting membrane exhibited a water flux of 36.43 L·m −2 ·h −1 and a reverse salt flux of 0.21 g·m −2 ·h −1 for FO mode, corresponding to 130.38 % and 89.51 % improvements, respectively, compared to the unmodified membrane. During lithium concentration tests, the membrane achieved a lithium concentration factor of 4.30 and a recovery rate of 96.38 %, representing improvements of 106.7 % and 13.5 % compared to the original membrane, respectively.