The large-scale preparation of monolayer 2D material remains a great challenge, which hinders its real application. Herein, we report a novel layered MOF, IPM-1, which is synthesized from a cage-like organic linker with extremely weak interlaminar interaction. When subjected to external disturbance, IPM-1 degenerated into an intermediate state between the crystalline and amorphous phase, in which the layers retain the in-plane two-dimension periodic structure but are misaligned in the third dimension, leading to the loss of apparent porosity and crystallinity. This amorphous IPM-1 is readily to be exfoliated into crystalline 2D nanosheets with a thickness of 1.15 nm at gram-scale, excellent thickness homogeneity, lateral size up to 10 μm, and restored microporosity. IPM-1 nanosheets exhibited high chemical stability and activity in the catalysis oxidation of alcohol, and combined the advantages of both homogeneous and heterogeneous catalyst. This work underlines that MOFs without apparent crystallinity can be idea precursors for the successful preparation of 2D crystalline monolayer nanosheets.