Fabrication Of Group Ⅳ Metal-Based Metal-Organic Frameworks For Photocatalytic Hydrogen Evolution

Metal-organic framework materials（MOFs）have informative prospects in application in the fields of gas adsorption and separation,sensor,and photocatalysis due to their high hydrothermal stability and multiple catalytic sites.Faced with the energy problem that needs to be solved urgently,the development and utilization of renewable resources to replace traditional fossil energy provides a new way to solve this problem.Group IV metal-based MOFs,especially Zr-based and Ti-based MOFs,have a wealth of structural types,and because of their excellent stability and outstanding characteristics and functional abilities,we can foresee that they will become one of the most promising MOF-based materials that can be used in practice.In this paper,we firstly designed and synthesized two Zr-based MOFs with different dimension but the same topology,and studied the effects of their different dimension on the performance of photocatalytic hydrogen production.In addition,our laboratory has firstly designed disk-shaped Ti-MOF ZSTU-1.On the basis of this material and different synthetic strategies,rod-shaped and sheet-shaped ZSTU-1 were synthesized,and the photocatalytic hydrogen production performance of the synthesized materials was studied.It is amazing that the morphology control has achieved previous goal that sheet-shaped ZSTU-1achieved the best photoactivity.The better ability in photocatalytic response using morphology control may provide a possible way for Ti-based MOFs to be used in photocatalytic activities.The main research contents are as follows:（1）Using the solvothermal synthetic method,we adjusted different experimental parameters to synthesize Zr-based MOFs with the same topology but different dimensions.First,Zr Cl₄ was selected as the zirconium source for 2D Zr-based MOFs,and TCA was selected as organic ligand for the new Zr-based MOFs.The organic ligand is reacted in a mixed solvent of DMF and concentrated hydrochloric acid at 120℃for 24 h to obtain a new type of 2D Zr-based MOFs;by selecting the same organic ligand,and in a mixed solvent of DMF and glacial acetic acid at 120℃,after 36 hours of reaction,another new type of 3D Zr-based MOFs was obtained.The different structures of the material were characterized by BET,XRD,SEM,UV,TG,IR and other analysis.The results showed that the 2D and 3D Zr-based MOFs designed and synthesized by different synthesis strategies have the same topological structure but different dimension.In particular,the fluorescence performance of those two MOFs is quite different;through the electrochemical impedance spectroscopy test,it has proved that charge mobility of 2D Zr-based MOFs is faster.In order to study the different photocatalytic abilities of these two MOFs with different dimension,photocatalysis has been tested under the irradiation of sunlight,the two MOFs exhibited different photocatalytic performance in the TEOA/Me CN/H₂O system.We believe that2D Zr-based MOFs can expose more active sites due to their two-dimensional structure,and therefore have better photocatalytic hydrogen production performance than the 3D analogue.At the same time,the photoluminescence test of the two different MOFs also showed that 2D Zr-based MOFs have better fluorescence performance.The recombination of photogenerated electrons and holes of 2D MOFs is effectively suppressed,which is also beneficial for its photocatalysis,and it is also an important reason why the performance of 2D Zr-based MOFs is better than 3D Zr-based MOFs.Then we tested the stability after catalysis,and the two different Zr-based MOFs materials still maintained good stability after three consecutive tests.In view of the research on the differences in performance of MOFs with the same topology but different dimension that have not been reported so far,this work in this paper provides a foreseeing avenue for relevant works.Designing MOFs with the same topology but different dimension,which can control their different responsive abilities under simulated sunlight irradiation,and can make a huge difference in their photocatalytic performance.（2）It has been reported that columnar and spherical Ti O₂ have different photoresponsive abilities in the long axis and short axis direction.It can be seen that the photocatalytic abilities of photocatalyst can be changed by morphology control.Ti-based MOFs with long infinite titanium oxide cluster chains provide a possible way to effectively adjust the photoresponsive ability through morphology control.Compared with the traditional Ti-based MOFs with separated titanium oxide clusters,our laboratory has reported a series of Ti-based MOFs with infinite titanium oxide cluster chains,ZSTUs.It has been proved that ZSTU-1 has a strong photocatalytic ability under visible light irradiation.We can add different regulators like glacial acetic acid and PVP to effectively control the synthesis of ZSTU-1 with different morphologies,and through BET,XRD,SEM,UV,TG,IR and other analysis,it is proved that the addition of the regulators does not destroy its pristine crystal structure.Through the electrochemical impedance spectroscopy test,it has proved that charge mobility of the sheet-shaped ZSTU-1 is faster,and the photocatalytic activity of the catalyst with different morphologies under visible light irradiation is tested in the TEOA/Me CN/H₂O system,which proved that the sheet-shaped ZSTU-1 show a higher photocatalytic ability.This work provides a possible way to realize the development of higher photocatalytic ability of Ti-based MOFs through morphology control,and proves Ti-based MOFs as potential materials in the field of photocatalysis.