Advancements in Janus two-dimensional materials: From basic theory to practical applications

Janus two-dimensional materials including transition metal dichalcogenides, transition metal carbides and carbonitrides, and metal-organic frameworks, exhibit unique electronic, optical, piezoelectric, and dielectric properties due to their asymmetric atomic structures, making them promising candidates for nanoelectronics, energy storage conversion and storage, and biomedical applications. This review comprehensively highlights the unique properties and typical applications of Janus two-dimensional materials and their van der Waals heterostructures. We explore the fundamental mechanisms underlying their electronic and optoelectronic properties, including band structures and light absorption. Strategies for enhancing their performance are discussed, providing a framework for addressing future research challenges. This comprehensive review integrates theoretical insights, synthesis techniques, and diverse applications, emphasizing the potential of Janus two-dimensional materials to revolutionize hydrogen production and other technological domains. We conclude by summarizing current advancements and future directions, offering inspiration for continued innovation in two-dimensional materials applications.