NH₂-UiO-66 Coated with Two-Dimensional Covalent Organic Frameworks: High Stability and Photocatalytic Activity

Abstract

The poor stability and low catalytic activity of NH2-UiO-66 in basic solutions require the reactions to be conducted in acidic solutions, which seriously hinders its potential photocatalytic application. Herein, we report that NH2-UiO-66 coated with two-dimensional covalent organic frameworks (COFs) via imine bond connection presents not only high photocatalytic activity but also high stability and adaptability to the solution environment. The NH2-UiO-66/COF hybrid material was fabricated through the Schiff base reaction of NH2-UiO-66 with 4,4′,4″-(1,3,5-triazine-2,4,6-triyl)­trianiline (TAPT) and 2,4,6-triformylphloroglucinol (TP). The hybrid material showed high stability in an alkaline environment, with only 4.7% of NH2-UiO-66 decomposed after the photocatalytic reaction. The optimum photocatalytic H2 evolution rate was 8.44 mmol·h–1·g–1 when triethanolamine was used as an electron-donating agent. The results presented here illustrate the possibility for effectively improving both the photocatalytic performance and stability of NH2-UiO-66 by coupling with COFs.

Heteroatom-doped carbon materials derived from covalent triazine framework@MOFs for the oxygen reduction reaction

“…18 The characteristic diffraction peaks at 2 θ = 11.1°, 12.7° and 20.4° in MC-24 correspond well to the MOF lattices (002), (111), and (113), demonstrating the formation of the MOF, while the diffraction peaks of the MOF were very weak, possibly due to the poorer crystallinity of MC-24. 48 The Raman spectra of MC-15-700, MC-24-700, and MC-33-700 all showed two typical characteristic peaks at around 1325 cm −1 (D band) and 1590 cm −1 (G band). The I D / I G ratios of MC-15-700, MC-24-700, and MC-33-700 were 0.96, 0.99, and 1.038, respectively.…”

MOF-COF Composite Photocatalysts: Design, Synthesis, and Mechanism

“…When they are excited by incident light to produce electron–hole pairs, the photogenerated electrons are transferred from the CB of semiconductor 1 that has a high reduction potential to the CB of semiconductor 2 that has a low reduction potential. , These are the most common MOF-COF heterojunctions used to facilitate the separation of photogenerated electrons and holes. Both of the semiconductors are able to be excited by incident light, and the VB holes and CB electrons migrate to each other, effectively inhibiting the compounding of photogenerated electrons and photogenerated holes. , For example, our group introduced TAPT-TP-COF into a MOF to obtain a II-scheme heterojunction NH 2 -UiO-66@TAPT-TP-COF photocatalyst for photocatalytic H 2 evolution and eventually found that the maximum photocatalytic H 2 evolution rate was 8 times and 2 times higher than those of the pure MOF and COF, respectively …”

“…(C) NH 2 -UiO-66/TAPT-TP-COF. Reproduced with permission . Copyright 2021 American Chemical Society.…”

“…Considering the solvent adaptability of the NH 2 -UiO-66, our group introduced TAPT-TP-COF to obtain a NH 2 -UiO-66/TAPT-TP-COF composite photocatalyst for photocatalytic hydrogen precipitation (Figure C). When triethanolamine was used as the electron donor, the hybrid material maintained a high degree of stability and photocatalytic performance in alkaline solutions, with an optimum photocatalytic hydrogen precipitation rate of 8.44 mmol h –1 g –1 . The amide bond also works well for a transfer of charge.…”

IL-functionalized Mn(ii)-doped core–shell Fe3O4@Zr-MOF nanomaterials for the removal of MB from wastewater based on dual adsorption/Fenton catalysis

“…Our recent work has shown that NH 2 -UiO-66 coupled with COF has high photocatalytic activity and good stability. 26 UiO-66 has good adsorption properties in aqueous environments. The adsorption capacity can be improved by doping with heterometallic modifications or post-synthetic modification strategies.…”