Two-dimensional (2D) oxide can be continuously produced by bubbling oxygen into liquid metals and the harvesting of these oxide relies on the proper choice of dispersion solvents.The mass-production of ligand-free 2D materials from high melting-point metals will not be possible if the limited stability of the traditional dispersion solvents is not circumvented.Herein,liquid tin was used for the first time in the bubbling protocol and 2D tin oxide was obtained in molten salts.The nanosheets were studied with combined microscopic and spectroscopic techniques,and high-density grain boundaries was identified between the sub-5-nm nano-crystallites in the nanosheets.It gives rise to the high performance in electrocatalytic CO2 reduction reaction.Density-functional-theory based calculation was applied to achieve a deeper understanding of the relationship between the activity,selectivity,and the grain-boundary features.The molten-salt based protocol could be explored for the synthesis of a library of functional 2D oxides.