Cerium-terephthalic acid metal-organic frameworks for ratiometric fluorescence detecting and scavenging·OH from fuel combustion gas.

Hydroxyl radical (•OH) in fuel combustion gas seriously damages human health. The techniques for simultaneously detecting and scavenging •OH in these gases are limited by poor thermal resistance. To meet this challenge, herein, metal organic frameworks (MOFs) with high thermal stability (80-400 °C) and dual function (•OH detection and elimination) are developed by coordinating Ce ions with terephthalic acid (TA) (Ce-BDC). Due to the reversible conversion between Ce3+ and Ce4+, and the high concentration of Ce3+ on the surface of Ce-BDC MOFs (89.6%), an •OH scavenging efficiency over 90% is realized. Ratiometric fluorescence (I440 nm/I355 nm) detection of •OH with a low detection limit of ∼4 µM is established by adopting Ce ions as an internal standard and TA as an •OH-responsive fluorophore. For real applications, the Ce-BDC MOFs demonstrate excellent •OH detection sensitivity and high •OH scavenging efficiency in gas produced from cigarettes, wood fiber and machine oil. Mouse model results show that the damage caused by •OH in cigarette smoke can be greatly reduced by Ce-BDC MOFs. This work provides a promising strategy for sensitively detecting and efficiently eliminating •OH in fuel combustion gas.

Growth of narrow-bandgap Cl-doped carbon nitride nanofibers on carbon nitride nanosheets for high-efficiency photocatalytic H2O2 generation.

Heterojunction construction has been proved to be an effective way to enhance photocatalysis performance. In this work, Cl-doped carbon nitride nanofibers (Cl-CNF) with broadband light harvesting capacity were in situ grown on carbon nitride nanosheets (CNS) by a facile hydrothermal method to construct a type II heterojunction. Benefiting from the joint effect of the improved charge carriers separation efficiency and a broadened visible light absorption range, the optimal heterostructure of Cl-CNF/CNS exhibits a H2O2 evolution rate of 247.5 µmol g-1 h-1 under visible light irradiation, which is 3.4 and 3.1 times as much as those of Cl-CNF (72.2 µmol g-1 h-1) and CNS (80.2 µmol g-1 h-1), respectively. Particularly, the heterojunction nanostructure displays an apparent quantum efficiency of 23.67% at 420 nm. Photoluminescence spectra and photocurrent measurements both verified the enhanced charge carriers separation ability. Our work provides a green and environmentally friendly strategy for H2O2 production by elaborate nanostructure design.