From 2D Primitives to 2D / 2D Heterostructures in Capacitive Deionization: A Platform for Versatile Ion Capture †

Comprehensive Summary Access to safe and clean water is fundamental to human health and economic development. While the practical impact of emerging technologies depends on their successful demonstration at large scales, capacitive deionization (CDI) has garnered significant attention as a promising approach for efficient desalination of seawater and brackish water. Among the various 2D materials explored for CDI (e.g., graphene, MXenes, covalent organic frameworks), their derived 2D/2D heterostructures, with unique lamellar morphology and interfacial engineering, offer an ideal platform for effectively modulating charge transfer behavior and ion diffusion. Despite a variety of 2D/2D heterostructures with diverse construction modes have been developed as CDI electrodes in recent years, a dedicated review focusing on the design strategies, synergistic effects, water desalination performance, and prevailing challenges remains lacking. In this review, we highlight the cutting‐edge research progress of 2D/2D heterostructures for CDI applications. After an overview of 2D materials and synthetic strategies of 2D/2D heterostructures, the relationships between the morphology/structure/composition and the water desalination performance are discussed in detail. Thereafter, we discuss current limitations and propose future directions for the rational design of 2D/2D heterostructures. This review will promote exploitation of 2D/2D heterostructures with an ideal performance of CDI towards water remediation. Key Scientists Significant progress has been made in the development of 2D/2D heterostructures for capacitive deionization (CDI) applications towards versatile ion capture. This collection of pioneering work underscores a clear trajectory in the field: the strategic construction of 2D/2D heterostructures is a powerful and versatile paradigm for advancing CDI. By intelligently combining different 2D materials, researchers have successfully engineered heterointerfaces with enhanced ion adsorption capacity, superior selectivity, and improved stability, paving the way for next‐generation, high‐performance desalination and water remediation technologies.