Beyond van der Waals: Modular Identification of 2D Materials in Strongly Bonded Layered Crystals.

Top-down exfoliation of layered solids has revolutionized materials innovation by enabling unprecedented access to atomically thin architectures. To expand the frontier of two-dimensional (2D) materials, it is imperative to systematically identify non-van der Waals (non-vdW) layered systems with strong interlayer bonding. While conventional atomic distance-based algorithms effectively identify vdW materials, they are considerably limited when applied to chemically bonded non-vdW systems due to their inherent bonding complexity. Here, we introduce a structural modularity paradigm that resolves dimensional identification challenges by removing specific elements from strongly bonded crystals to construct artificial substructures from residual atoms. Coupled with the appropriate layer-recognition algorithms for vdW lattices, this approach reveals 8,889 hidden 2D modules across 30,147 ternary compounds, of which 80.6% are undetectable by traditional layer-detection approaches. These findings show that non-vdW layered solids significantly outnumber vdW counterparts (1,383), highlighting a vast chemical space for 2D materials exploration. High-throughput thermodynamic screening of 15,312 ternary oxides identifies 1,083 chemically stable 2D modules exfoliable via a proton exchange-assisted method. Validation against 15 experimentally reported 2D oxide nanosheets, along with the first synthesis of ultrathin HxRuO3 nanosheets from non-vdW Na2RuO3 crystal, confirms the reliability and predictive strength of this method for both known and previously unexplored systems.