Metal organic frameworks (MOFs) {[Zn₂(L₁)₂(SDB)₂]·H₂O}_n (MOF₁), [Zn₂(L₂)(SDB)₂]_n (MOF₂) and [Zn₂(L₃)(hfipbb)₂]_n (MOF₃) (L₁ = 4,4′-(2,5-dimethyl-1,4-phenylene)bis(ethene-2,1-diyl))dipyridine), L₂ = (E,E,E)-1,6-bis(4-pyridyl)-l,3,5-hexatriene, L₃ = 4,4′-((2-methyl-1,4-phenylene)bis(ethene-2,1-diyl))bipyridine, H₂SDB = 4,4′-sulfonyldibenzoic acid, H₂hfipbb = 2,2-bis(4-carboxyphenyl) hexafluoropropane) were prepared by hydrothermal synthesis. Weak van der Waals forces were observed between 2D layers in MOF₁ and MOF₂. The weak interlayer interactions could be cleaved by external mechanical force and bulk samples were exfoliated into single-layer two-dimensional nanosheets by ultrasound in ethanol. Single-layer MOF nanosheets which had a lateral size of approximately 2 µm were generated after ultrasound treatment of MOF₁ and MOF₂. However, 3D coordination network of MOF₃ could not be successfully exfoliated because of its different network structure. MOF₁ and MOF₂ nanosheets dispersed in ethanol displayed strong photoluminescence (PL), which could be quenched specifically by folic acid (FA) through a concentration dependent manner. This hypersensitive and fast luminescence sensing benefited from numerous active sites and broad specific surface area of these ultrathin nanosheets.