Cellulose Nanocrystals as Template for Improving the Crystallinity of Two-Dimensional Covalent Organic Framework Films

Abstract

Despite the rapid development of two-dimensional covalent organic frameworks (2D COFs) in recent years, it remains a great challenge to synthesize highly crystalline COF materials. Here, a CNC-assisted approach was adopted to synthesize high crystallinity COF materials. A series of 2D COF films were synthesized at the air–water interface by using cellulose nanocrystals (CNCs) as the template. The occurrence of Schiff reactions based on the imine bond was demonstrated by Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR). Scanning electron microscopy (SEM) exhibited the appearances of 2D COF films were flower-like. When CNCs were added to a certain extent, the size of a single petal in the flowers gradually increased with the amount of CNCs. The film with large petals was characterized by Ultraviolet–Visible diffuse reflectance spectroscopy (UV–Vis DRS), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). In UV–Vis DRS curves, the S-band of COF-366 film was red-shifted by 24 nm compared with that of 5,10,15,20-tetrakis(4-aminophenyl)-21H,23H-porphyrin (TAPP), confirming the existence of extended conjugation in COF-366 film. XPS was used to identify the surface composition of the sample. The N1s signal of the film indicated that each TAPP formed four imine bonds with 2,5-dihydroxyterephthalaldehyde (DHTA) in COF-366 film. TEM images showed that CNCs had an influence on the crystal size. It was observed from SAED that the crystallinity of the film with CNCs was higher than the film without CNCs. This work provided a new template for improving the crystallinity of 2D COF films.

AuNPs-COFs Core–Shell Reversible SERS Nanosensor for Monitoring Intracellular Redox Dynamics

“…The N 1s spectra of AuNPs@2-MBQ@COFs were divided into 398.55 and 399.40 eV corresponding to CN and −NH 2 , respectively . And there were two peaks at 531.40 and 532.45 eV in O 1s spectra, which belonged to the CO group and air contamination . The XPS spectra of S 2p and Au 4f indicated that the 2-MBQ was modified on the surface of AuNPs according to the Au–S bond .…”

“…51 And there were two peaks at 531.40 and 532.45 eV in O 1s spectra, which belonged to the C�O group and air contamination. 52 The XPS spectra of S 2p and Au 4f indicated that the 2-MBQ was modified on the surface of AuNPs according to the Au−S bond. 53 From the SERS spectra of AuNPs@2-MBQ@COFs and AuNPs@2-MBQ shown in Figure 2D, the bands located at 840 cm −1 (stretching vibration of C�O and CCC) and 985 cm −1 (stretching vibration of C�O and bending vibration of CCC) belonged to the characteristic peak of 2-MBQ molecules.…”

Photoresponse of CVD grown crystalline quantum dot-embedded covalent organic framework thin film

“…As seen in the gure, the thin-lm shows the characteristic absorbance peaks are observed at 470 nm [Soret (S) band] and 575 nm [Q band]. 58 The slight redshi of the absorption edges observed may be due to the presence of QD's in the COF thinlm. To further understand the structural information of the COF366-QDs lm, it was examined by high-resolution X-ray photoelectron spectra (XPS).…”

“…Another peak with higher binding energy and a minor peak at around 397.7 eV and 400.3 eV was observed representing non-protonated nitrogen structure and Ph-NH 2 of porphyrin in 3b). 55,58 The surface topology analysis of the thin-lm (S3) was studied by atomic force microscopy as shown in Fig. 4a-c and the average thickness of the COF366-QD thin lm was found to be ∼112 nm (Fig.…”

“…50 COF-366 is one of the pioneering and promising porphyrin based-COF with very high charge carrier mobility reported by Yaghi and co-workers and later several research groups presented applications of COF-366. [54][55][56][57][58] However, chemically stable, crystalline, and large area-growth of porphyrin-containing COF-366 using chemical vapor deposition technique has not been explored much and therefore a modest attempt has been made here. Here, we present our tactically controlled fabrication of COF by imine condensation of 5,10,15,20-tetrakis(4aminophenyl)porphyrin (TAPP) with 1,4-benzenedicarboxaldehyde (BDA) by chemical vapor deposition (CVD) to fabricate COF366-QD based photoactive device.…”