Graphene Oxide-Assisted Covalent Triazine Framework for Boosting Photocatalytic H2 Evolution.

Covalent triazine frameworks (CTFs) with two-dimensional structures have exhibited promising visible-light-induced H2 evolution performance. However, it is still a challenge to improve their activity. Herein, we report π-conjugation-linked CTF-1/GO for boosting photocatalytic H2 evolution. The CTF-1/GO hybrid material was obtained by a facile low-temperature condensation of 1,4-dicyanobenzene in the presence of GO. The results of photocatalytic H2 evolution indicate that the optimum hybrid, CTF-1/GO-3.0, exhibited an H2 evolution rate of 2262.4 µmol ⋅ g-1 ⋅ h-1 under visible light irradiation, which was 9 times that of pure CTF-1. The enhanced photocatalytic performance could be attributed to the fact that GO in CTF-1/GO hybrids not only acts as an electron collector and transporter like a "bridge" to facilitate the separation and transfer of photogenerated charges but also shortens the electron migration path due to its thin sheet layer uniformly distribution over CTF-1. This work could help future development of novel conjugated CTF-based composite materials as high-efficiency photocatalyst for photocatalysis.

A low-polarity small organic molecule with a stable keto form for photocatalytic H2 evolution.

Five small organic molecules (SOMs) with different degrees of enol to keto tautomerism were synthesized for photocatalytic H2 evolution. The SOM possessing the highest activity features a stable keto form that greatly facilitates the flowing of the excited electrons toward the carbonyl O site where the reduction reaction occurs.

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

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.