A General Modular Assembly Approach to a Library of Hybrid Superlattices

Hybrid superlattices consisting of two-dimensional atomic crystals (2DACs) and self-assembled molecular layers allow to synergistically combine rich physical properties in solid-state 2DACs with designable molecular functionalities. Such hybrid superlattices are generally prepared by a direct chemical or electrochemical intercalation approach, and are often limited to a specific class of 2DACs or molecular systems as dictated by the relative chemical reactivity and electrochemical stability of the constituent building blocks. Self-assembly offers an alternative strategy for efficiently organizing multiple building units into ordered superstructures. In this work, we report a systematic and quantitative study of the underlying governing principle for electrostatic assembly strategy in the context of 2D-molecular hybrid superlattices, and explore it for constructing a broad library of hybrid superlattices with widely variable compositions and tunable structural configurations. By using exfoliated MoS₂ as a model system, we show a series of amines, amino acids, coordination complexes, and polymers can be assembled with MoS₂ monolayers, forming alternatively ordered hybrid superlattices. Our systematic studies reveal that electrostatic assembly process is highly analogous to classical co-precipitation of ionic solids and fundamentally governed by the charge balance and equilibrium between electrostatic repulsion and van der Waals (vdW) interaction, following Schulze-Hardy rule at Debye–Hückel approximation based on Derjaguin–Landau–Verwey–Overbeek (DLVO) colloidal theory. Based on the charge balance rule, the layer number of inclusive molecules in the resulting hybrid superlattices can be precisely tuned. Furthermore, we show this assembly strategy is highly general and can be extended to diverse 2DACs, such as TiS₂, TaS₂, WS₂, MoSe₂, SnSe, In₂Se₃, Bi₂Se₃ and Mxenes such as Ti₃C₂T_x. The formation of hybrid superlattices with functional ions or molecules opens a new dimension to tailor and tame the fundamental physical properties of the 2DACs and enables artificial materials with exotic functions. For example, the formation of TaS₂/amine superlattice notably elevates the superconducting transition temperature (<i>T</i>_c). The introduction of chiral amino acids into MoS₂ interlayers effectively incorporates molecular chirality into solid-state superlattices, and the formation of MoS₂/Co(en)₃Cl₃ superlattice induces ferromagnetic properties not available in either constituent. Together, our study defines a general modular approach for the rational assembly of hybrid superlattices and artificial solids with designable structural motifs and widely tunable physical properties.