Covalent Organic Framework Nanosheets for Fluorescence Sensing via Metal Coordination

Abstract

Covalent organic framework nanosheets (COF NSs) provide well-ordered π–π structures that can be used to develop luminescent materials. However, most COF NSs have problems of weak luminescence and low fluorescence quantum yield. In this work, we prepared covalent organic framework nanosheets (Bpy-NSs) with good water dispersibility, nitrogen-rich functional groups, and regular pore structure. We explored the coordination of Bpy-NSs with Al3+ to eliminate the fluorescence quenching process caused by photoinduced electron transfer (PET). Thus, the fluorescence “turn-on” signal linearly increases with Al3+ concentration, achieving a 15.7-fold improved in fluorescence, and the absolute fluorescence quantum yield increased from 0.15 to 1.74%. Furthermore, this is the first COF fluorescence sensor that can be used for high sensitivity and selectivity detection of Al3+ in the aqueous phase. We anticipate that the expansion of metal ions coordination strategy in the aqueous phase will not only significantly enhance the fluorescence of COF NSs but also extend the functional range of COF NSs.

Regenerable and stable sp2 carbon-conjugated covalent organic frameworks for selective detection and extraction of uranium

“…The Brunauer-Emmett-Teller (BET) surface area of TFPT-BTAN was determined to be 1062 m 2 g −1 , and the pore-size distribution centered at 1.44 nm based on non-local density functional theory, which matches well with the model (Fig. 2b) 30 .…”

“…Covalent organic frameworks (COFs) are a class of porous crystalline polymers with significant advantages for application in catalysis [14][15][16][17][18] , gas storage [19][20][21][22] , and metal ion extraction [23][24][25][26][27] owing to excellent chemical and thermal stability, flexible topological connectivity, and tunable functionality [28][29][30] . COFs with tunable porosity and large specific surface area might be ideal for extracting radionuclides such as UO 2 2+ .…”

“…7b) both show that TFPT-BTAN-AO retained the same characteristic peaks after the treatments, confirming its remarkable chemical stability. In order to reflect the superior stability of TFPT-BTAN-AO compared with other COFs, two β-ketoenamine COFs (Tp-Bpy and Tp-BD) were synthesized by the reported method 30 . After treatment with high concentrations of nitric acid (3.0 M and 5.0 M), the crystallinity of Tp-Bpy and Tp-BD was completely destroyed (Supplementary Fig.…”

Nanoscale covalent organic frameworks as theranostic platforms for oncotherapy: synthesis, functionalization, and applications

“…151 Some examples for the preparation of NCOFs by ultrasonic exfoliation are shown in Table 2. [150][151][152][153][154][155][156][157][158][159][160][161][162][163][164][165] Evidently, the weaker the interactions between the COF layers, the easier it becomes to perform ultrasonic exfoliation. TPA-COF constructed with tris(4-aminophenyl)amine and tris(4-formylphenyl)amine exible monomers with the C 3v symmetry conrmed this prediction.…”

Emerging porous nanosheets: From fundamental synthesis to promising applications

“…Meanwhile, the sonication also plays an important role in the synthesis of MOF and COF nanosheets from corresponding layer-structured bulk materials [45,46]. The weak interactions between layers of MOFs and COFs are easy to overcome due to the high energy of shear force or bubbles produced by sonication in suitable solvents, contributing to the synthesis of MOF and COF nanosheets [47][48][49][50][51][52][53]. The efficiency of exfoliation is usually affected by several key factors.…”