Photocatalytic Selective Oxidation Reactions Over Metal-organic Frameworks Based On Group ⅣB Elements

Clean and renewable solar-powered photocatalytic selective organic transformations can efficiently and selectively convert substrates into target products.These transformations are one of the most effective strategies to solve energy problems and alleviate the increasingly severe environmental issues at the source.The key to achieving these goals is to construct new photocatalytic systems based on porous materials.Metal–organic frameworks（MOFs）are potential photocatalytic materials due to their high specific surface areas,decent crystallinity,and adjustable pore channels,etc.Therefore,applying MOFs in photocatalytic selective organic transformations is feasible.In this context,MOF-based photocatalytic systems are established for the selective oxidation of organic sulfides and amines.Firstly,we successfully synthesize 2D and 3D porphyrin Ti-based MOFs,namely2D PMOF（Ti）and 3D PMOF（Ti）,and apply them for red light-driven photocatalytic selective oxidation of sulfides.Experiments and characterizations demonstrate that 2D PMOF（Ti）has better photocatalytic activity due to the more exposed active sites,higher specific surface area,and better optoelectronic performance.Furthermore,we also investigate the effects of synthetic solvents on the structure and function of 2D PMOF（Ti）for the activity of selective oxidation of amines.The red light-driven photocatalytic selective oxidation system over MOFs is successfully established in this work.Secondly,we synthesize MOFs through the coordination of two different Zr-nodes and porphyrin ligands,namely PCN-222（Zr₆（μ-OH）₈ cluster）and PCN-226（Zr O₇zigzag chain）.Two MOFs are applied for photocatalytic selective oxidation of sulfides with TEMPO or HOOC-TEMPO,respectively.Experimental characterizations and theoretical calculations certify that the hydroxyl group on MOFs and the carboxyl group on TEMPO can chelate with each other,thus exhibiting an excellent photocatalytic cooperative effect.This work demonstrates the potential and application prospect of MOFs and TEMPO cooperative photocatalytic system for efficient selective oxidation.Finally,we replace porphyrin organic linkers with pyrene organic linkers to synthesize NU-1000.We further replace metal Zr with Hf to synthesize Hf-NU-1000,to explore the cooperative effect between two MOFs and HOOC-TEMPO on the photocatalytic selective oxidation of amines and sulfides.The results confirm that HOOC-TEMPO has better photocatalytic cooperative effects with two MOFs,and the activity could be increased more than three times.This work further broadens the application of cooperative photocatalysis between HOOC-TEMPO and MOFs and demonstrates that the system has a promising future.In conclusion,we have successfully constructed three photocatalytic systems based on MOFs for the selective aerobic oxidation of sulfides and amines.This study verifies the influence on the structure and function of MOFs and extends the application of cooperative photocatalytic strategy,offering significant insights and valuable perspectives.