Linker Engineering for Reactive Oxygen Species Generation Efficiency in Ultra-Stable Nickel-Based Metal-Organic Frameworks

Interfacial charge transfer on the surface of heterogeneousphotocatalystsdictates the efficiency of reactive oxygen species (ROS) generationand therefore the efficiency of aerobic oxidation reactions. Reticularchemistry in metal-organic frameworks (MOFs) allows for therational design of donor-acceptor pairs to optimize interfacialcharge-transfer kinetics. Herein, we report a series of isostructural fcu-topology Ni-8-MOFs (termed JNU-212, JNU-213, JNU-214, and JNU-215) with linearly bridged bipyrazoles as organic linkers. These crystallineNi(8)-MOFs can maintain their structural integrity in 7 MNaOH at 100 & DEG;C for 24 h. Experimental studies reveal that linkerengineering by tuning the electron-accepting capacity of the pyrazole-bridgingunits renders these Ni-8-MOFs with significantly improvedcharge separation and transfer efficiency under visible-light irradiation.Among them, the one containing a benzoselenadiazole unit (JNU-214) exhibits the best photocatalytic performance in the aerobic oxidationof benzylamines with a conversion rate of 99% in 24 h. Recycling experimentswere carried out to confirm the stability and reusability of JNU-214 as a robust heterogeneous catalyst. Significantly,the systematic modulation of the electron-accepting capacity of thebridging units in donor-acceptor-donor MOFs providesa new pathway to develop viable noble-metal-free heterogeneous photocatalystsfor aerobic oxidation reactions.

Automated summary

Interfacial charge transfer on the surface of heterogeneous photocatalysts plays a crucial role in determining the efficiency of reactive oxygen species (ROS) generation and aerobic oxidation reactions. In this study, we used reticular chemistry in metal-organic frameworks (MOFs) to design a series of isostructural Ni-8-MOFs with linearly bridged bipyrazoles as organic linkers. These crystalline Ni(8)-MOFs demonstrated improved charge separation and transfer efficiency under visible-light irradiation due to the electron-accepting capacity tuning of the pyrazole-bridging units. Among them, JNU-214, which contained a benzoselenadiazole unit, exhibited the highest photocatalytic performance in the aerobic oxidation of benzylamines.