▎ 摘　　要

NOVELTY - Two-dimensional metal organic framework (2D MOF) comprises many multivalent metals or metal ions and many multidentate ligands arranged to form a crystalline structure having a lateral size of at least 2.5 mu m and a thickness of less than or equal to 5 nm. USE - The 2D MOF is useful in a substrate of an electrode or an electrochromic device (all claimed) e.g. smart windows i.e. for cars, trains, airplanes and buildings, and flexible displays i.e. for signs, tablets, phones and computer monitors. ADVANTAGE - The 2D MOF: stores the memory of the voltage applied to it without requiring the need of application of continuous voltage; provides more than four colors, by applying different voltages; and provides a device that can maintain excellent discoloration effect and mechanical stability in the process of bending 1000 times. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for: (1) preparing (M1) a metal oxide nanosheet, comprising mixing a metal containing precursor with a surfactant at a high temperature for a period of time, where the produced metal oxide nanosheet has a lateral size of at least 5 mu m and a thickness of less than or equal to 5 nm; (2) preparing (M2) the 2D MOF, comprising reacting a metal oxide compound suspended in a liquid with a multidentate ligand dissolved in the liquid, where the reaction occurs while at least a portion of the metal oxide compound is not dissolved in the liquid, and the product 2D MOF is at least partially insoluble in the liquid; and (3) a substrate comprising on at least part of a surface of the substrate the 2D MOF.