Studies On Synthesis And Photocatalytic Property Of Triptycene-Based Semiconductor Composites For Hydrogen Evolution

In recent years,energy and environmental issues have become more and more serious,thus it is urgent to find clean and renewable energy.Hydrogen,acting as an environmental-friendly and clean energy source,is considered to beoneofthemostimportantreplacementsoffossilfuels.Semiconductor-based photocatalytic hydrogen production is a challenging and promising approach to solve energy crises and reduce environmental pollution.Organic porous polymers have large specific surfaces and excellent pore structure,making its gas storage and separation well as well as great photocatalysis.Some conventional photocatalysts,such as TiO₂,have limited developments in photocatalytic reactions due to the large band gap.Therefore,it is meaningful to combine semiconductors with porous organic polymers building heterostructures which could enhance the photocatalytic activity of semiconductors.In our study,the combination of triptyceneyl microporous polymers and semiconductor effectively reduces the agglomeration of semiconductor during the preparation.A series of photocatalysts with excellent effects have been successfully prepared by reasonable valence band theory.The main research contents are as follows:（1）Triptyceneyl microporous polymers have been designed and synthesized.The nitration reaction of triptycene with concentrated nitric acid givestwoisomers,namely2,6,14-trinitrotripadeneand2,7,14-trinitrotripadene.The main products 2,6,14-trinitrotriptycene was reacted with Raney Ni and hydrazine monohydrate under nitrogen protection to reduce the nitro group,then 2,6,14-triaminotriptycene was generated.The2,6,14-triaminotriptycenewasfurthersubstitutedwithconcentrated hydrobromic acid in the presence of CuBr and NaNO₂ to obtain2,6,14-tribromotriptycene.Finally,the 2,6,14-tribromotrimonene was reacted withtwokindsofligands1,4-phenylenebisboronicacidand4,4′-biphenyldiboronic acid respectively to obtain two kinds of Suzuki coupling reaction products.The two novel triptyceneyl microporous polymers were named TCP and TMP respectively.The structure of the novel triptyceneyl microporous polymer is characterized by liquid-state ¹H NMR spectra,solid-state ¹³C NMR spectra,fourier transform infrared spectroscopy（FT-IR）.（2）TCP-Cd_0.5Zn_0.5S composite photocatalyst was prepared and some studies on its photocatalytic hydrogen production performance were did.Basing on the triptyceneyl microporous polymer TCP,the novel TCP-CZS composite photocatalyst was successfully prepared in situ precipitation method.It was observed that the Cd_0.5Zn_0.5S was uniformly coated on the external surface of TCP by the SEM and TEM.By screening a series of different mass composite ratios of TCP and Cd_0.5Zn_0.5S,TCP-CZS5 was found as the excellent composite photocatalyst.With Na₂S and Na₂SO₃ being acted as the sacrificial agent,the hydrogen production rate of TCP-CZS5reached 50670μmol h^-1 g^-1 under the continuously irradiated by 300 W visible light for 3 h.（3）CdS@TCP core-shell composite photocatalyst was prepared and some studies on its photocatalytic hydrogen production performance were did.The triptycene polymer TCP was coated on the nanorod-shaped cadmium sulfide（CdS-NR）.Meanwhile,the core-shell structure of CdS@TCP and its good response to visible light were proved by XRD,IR,UV-vis,PL,Raman,BET and other characterization methods.The morphologies of CdS@TCP as well as the elements and states contained therein were also explored by SEM,TEM,HRTEM,Mapping,XPS and other characterization methods.Under the same experimental conditions,the hydrogen production rate of CdS@TCP-4was as high as 104515μmol h^-1 g^-1,which was 2 times higher than that of（1）.（4）Cd_0.5Zn_0.5S quantum dots@TMP composite photocatalyst was generated and some studies on its photocatalytic hydrogen production performance were did.On the basis of the previous experiments,a novel triptyceneyl microporous polymer TMP was designed and synthesized by replacing the new boronic acid ligand 4,4′-biphenyldiboronic acid.The effects of polymer chain length on hydrogen production was investigated.First of all,the CZS QDs@TMP composite photocatalyst was successfully prepared by precipitation method.Then,it was observed by SEM and TEM that the granular Cd_0.5Zn_0.5S was uniformly distributed on the spherical triptycene polymer TMP.Under the same illumination conditions,the hydrogen production effect was optimized.The hydrogen production rate of CZS QDs@TMP-1 was as high as 81327μmol h^-1 g^-1,which was 1.6 times higher than that of（1）.