## 3 Results and Discussion  
As shown in Figure 1a, the Cu-ETTC MOF sheet was synthesized by reacting 4,4,4,4-(ethene-1,1,2,2-tetrayl)tetrabiphenyl-4-carboxylic acid and copper(II) nitrate hydrate in N,N-dimethylformamide (DMF) solvent using the bottom-up method. Based on the limitations of intramolecular rotation, in theory, H\({}_{4}\)ETTC will release excitation energy mainly in the form of AIE effect after forming the MOF structure. However, the Cu-ETTC MOF sheet also suffers from the intermolecular LMCT process, resulting in the opposite phenomenon and an aggregation-caused quenching effect. Figure 1b shows the photograph images obtained under natural light and 365 nm wavelength conditions, where the fluorescence of Cu-ETTC is almost completely quenched. Then, the chemical structure and morphology of the Cu-ETTC MOF sheet were analyzed using a UV-vis absorption spectra, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). As shown in Figure 1c, the H\({}_{4}\)ETTC exhibited a broad absorption profile with three discernible feature peaks at 291, 318, and 362 nm. With the formation of the Cu-ETTC MOF sheet, a significant absorption peak appeared at 272 nm, and the position of the strongest absorption peak changed from 291 to 324 nm,which confirmed the coordination chelation reaction between copper ions and H4 ETTC. In addition, there was a linear relationship between the UV-vis absorption intensity of Cu-ETTC and its copper-ion concentration (copper ions were determined using inductively coupled plasma mass spectrometry, ICP-MS), and the linear regression equation was \(y\) = 0.0076 + 0.0193\(x\) with the correlation coefficient of 0.99 (Figure 1d,f). This linear relationship was useful for subsequent quantitative analysis. The formation of the Cu-ETTC MOF sheet was also verified using FT-IR. With the formation of a coordination bond, the absorption peak of the C=O stretching vibration representing a carboxyl group at 1681 cm\({}^{-1}\) disappeared, while a new absorption peak appeared at 1657 cm\({}^{-1}\) (Figure 1e), which is consistent with the literature [39]. The strong peak at 3430 cm\({}^{-1}\) and the obvious small peak at 2925 cm\({}^{-1}\) belonged to the stretching bands of O-H and C-H, while the strongest peak at 1391 cm\({}^{-1}\) came from the symmetric COO- stretching vibration. Figure 1: (**a**) Schematic of the preparation process, (**b**) photograph images, (**c**) UV-_Vis_ absorption, and (**e**) FT-IR spectra of the Cu-ETTC MOF sheet. (**d,f**) Absorption curves and correlation linearity of the Cu-ETTC MOF sheet with different concentrations. The prepared Cu-ETTC MOF has an obvious two-dimensional ultrathin-layered morphology with a graphene-like multi-wrinkled structure, linked at a micron size. As shown in Figure 2a, after reducing the proportion of coordinated metals, the MOF material still had a lamellar structure, but the wrinkles were significantly reduced, showing a separate lamellar morphological distribution with different particle sizes. Therefore, a more homogeneous MOF material was selected for research in this study, that is, the sample obtained as the Cu(NO\({}_{3}\))\({}_{2}\)/H\({}_{4}\)ETTC reaction ratio was 2/1. To elucidate the elemental information of the Cu-ETTC MOF sheet, XPS analysis was carried out. The C, O, and Cu elements appeared in the XPS spectrum of the Cu-ETTC MOF sheet, and their contents were 84.36, 13.9, and 1.74%, respectively. As shown in Figure 2d, the binding energy (BE) peaks at 935.0 and 954.9 eV were assigned to Cu\({}^{2+}\), accompanied by the characteristic shakeup satellite peaks at 940.2, 944.2, 960.1, and 963.2 eV. The BE peaks of Cu 2p\({}_{3/2}\) and Cu 2p\({}_{1/2}\) at 933.4 and 953.2 eV, respectively, confirmed the presence of a large amount of Cu\({}^{+}\) in the Cu-ETTC MOF structure. This result also demonstrated that the Cu-ETTC MOF sheet has a significant LMCT process, and this process annihilates the matrix coordination-induced emission (MCIE) effect.