1 Institute of Materials Research, Center of Double Helix, Guangdong Provincial Key Laboratory of Thermal Management Engineering and Materials, Shenzhen Key Laboratory of Advanced Layered Materials for Value-added Applications, Institute of Materials Research, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, 518055, P. R. China.
2 Xi'an Research institute of High Technology, Xi'an, 710025, P. R. China.
3 Department of Physics and Astronomy, Rensselaer Polytechnic Institute, Rensselaer, NY, 12180, USA.
4 Department of Physics, Department of Chemistry, Department of Materials Science and Engineering, Center for 2D and Layered Materials, The Pennsylvania State University, University Park, PA, 16802, USA.
5 Southern University of Science and Technology, Shenzhen, 518055, China.
6 Department of Chemical and Materials Engineering, Department of Physics, and Centre for Nano Science Research (CeNSR), Concordia University, Montreal, H4B1R6, Canada.
7 Institute of Superlubricity Technology, Research Institute of Tsinghua University in Shenzhen, Shenzhen, 518057, China.
8 Shenzhen Geim Graphene Center, Tsinghua-Berkeley Shenzhen Institute and Institute of Materials Research, Shenzhen Key Laboratory of Advanced Layered Materials for Value-added Applications, Institute of Materials Research, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, 518055, P. R. China.

Liquid exfoliation is a scalable and effective method for synthesizing 2D nanosheets (NSs) but often induces contamination and defects. Here, liquid metal gallium (Ga) is used to exfoliate bulk layered materials into 2D NSs at near room temperature, utilizing the liquid surface tension and Ga intercalation to disrupt Van der Waals (vdW) forces. In addition, the process can transform the 2H-phase of transition metal dichalcogenides into the 1T'-phase under ambient conditions. This method produces high aspect ratio, surfactant-free 2D-NSs for more than 10 types of 2D materials that include h-BN, graphene, MoTe₂, MoSe₂, layered minerals, etc. The subsequent Ga separation via ethanol dispersion avoids the formation of additional defects and surfactant contamination. By adjusting initial defect levels of the layered materials, customize the metallicity and/or defectiveness of 2D NSs can be customized for applications such as birefringence-tunable modulators with exfoliated h-BN, and enhanced hydrogen evolution with defective MoS₂. This approach offers a strategy to optimize liquid metal/2D interfaces, preserving intrinsic properties and enabling practical applications, potentially transforming optics, energy conversion, and beyond.