Preparation And Application Of Flower-Like Porphyrin-based Metal Organic Framework Material

Metal-organic framework materials(MOFs)have the structural characteristics of large specific surface area,adjustable pore size,and easy functional modification of ligands.It has good application prospects in many fields such as gas adsorption and separation,slow drug release,heterogeneous catalysis,and sensing.The porphyrin-based MOFs synthesized with porphyrin and its derivatives as ligands not only possess the unique biochemical properties of porphyrin molecules,but also have the characteristics of MOFs,exhibiting excellent light absorption properties and catalytic activity.The catalytic performance of MOFs is not only related to its molecular structure,but also depends on its appearance and morphology.Among so many morphologies such as powder,block,spherical,tube,flower,etc.,the flower-like appearance has better stability,it enables more active sites to be exposed and fully utilized.Compared with other morphologies,it has a larger specific surface area and has better application prospects in catalysis applications.However,precise control the size and morphology of MOFs still faces great challenges.First,three inorganic acids and three organic acids are used as morphology control agents to regulate the synthesis process of porphyrin-based MOFs,and promote their self-assembly into the flower-like morphology.The study found that only the addition of trifluoroacetic acid can synthesis of flower-like porphyrin-based MOFs,and by studying the influence of the addition amount of trifluoroacetic acid on the final morphology of Cu-TCPP,we found that the optimal addition amount of trifluoroacetic acid was determined to be 0.625 ?L/mL.This method has been successfully extended to the morphology control of other divalent metalloporphyrin-based MOFs,which proves that the method has good versatility.Then,used various characterization methods such as FTIR,UV-vis,XRD and XPS to characterize the porphyrin-based MOFs we synthesized in detail.The results showed that we synthesized the M-TCPP type MOFs in which the pyrrole ring center of TCPP was metalized.At the same time,we also carried out SEM characterization by sampling and drying at different times during the synthesis process,studied the synthesis process and proposed a possible self-assembly mechanism.After that,chosen flower-like Cu-TCPP with the highest yield,the shortest synthesis time and have the most complete flower-like morphology as the research object,and explored its adsorption performance for single organic dyes and mixed organic dyes.The results showed that flower-like Cu-TCPP has the best adsorption effect on a single methylene blue,with an adsorption rate of attached about 90%,and selective adsorption for mixed dye solutions,which is mainly due to electrostatic interaction and size limitation effects.Finally,due to the excellent photosensitivity of porphyrin-based MOFs,we chose flower-like Cu-TCPP as the photocatalyst.Rhodamine B(RhB),which has large molecular size,high color rendering,and was widely used,was chosen to be decomposed.The photocatalytic performance of flower-like Cu-TCPP on RhB and the photocatalytic mechanism have been researched.The results prove that flower-like Cu-TCPP has good photocatalytic performance,and it can still maintain the structure and morphology after five cycles of use,which has the potential for practical application.Through the radical trapping experiments and analysis of the band gap,valence band and conduction band position of flower-like Cu-TCPP,results prove that the free radicals that play an important role during the photocatalytic reaction are holes(h+),superoxide radicals(·O2-)and hydroxyl radicals(·OH),among them,h+and ·O2-play the main role.