Corrole-TiO₂ Composite Catalyst:Synthesis And Photocatalytic Degradation Of Environmental Pollutants

Corroles,as new member of porphyrinoid dyes family,are structurally similar as porphyrins,but contain a direct carbon-carbon bond between two pyrrole rings and carry three N-H protons in the inner core.They possess a smaller four-nitrogen cavity but can stabilize the central metal ion of the complex in a formally higher oxidation state than for the related porphyrins.Moreover,corroles can have different substituents at the peripheral positions of the molecular framework,and a judicious selection of the placement and properties of the substituents or the central metals enables tuning of the frontier orbitals and resulting in the optical,electrical,and electrochemical properties.These properties of corroles are particularly appealing for investigated applications of the compounds in the fields of catalysis,chemical sensors,dye-sensitized solar cells,nonlinear optical material,and/or photodynamic therapy.In order to expand the applications of carrroles,a series of organic-inorganic photocatalysts?corrole-TiO₂?were prepared by chemically or physically grafted onto the surface of TiO₂ in this work.Acid black 1?AB1?and rhodamine B?RhB?were selected as representative organic pollutants to demonstrate the photocatalytic performance of the prepared photocatalysts under visible light.In addition,the possible photocatalytic degradation mechanism was also discussed in detail.The main studies are as follows:1.Photocatalytic degradation of acid black 1 by corrole chemically modified GPTMS/TiO₂ nanoparticlesA new organic-inorganic TNPC-GPTMS/TiO₂ photocatalyst was achieved by5,10,15-tris-?4-aminophenyl?corrole?TNPC?chemically grafted onto the surface of glycidoxypropyltrimethoxy silane?GPTMS?modified TiO₂?GPTMS/TiO₂?.The prepared photocatalyst was fully characterized by various spectroscopic?DRS,Raman and FT-IR?and electron microscopic?TEM and SEM?investigations confirming the chemical formation of the target photocatalyst.The photocatalytic property of TNPC-GPTMS/TiO₂ towards the photocatalytic degradation of di-anionic azo dye Acid Black 1?AB1?was comparatively assessed with the pure TiO₂ and GPTMS/TiO₂ under visible light irradiation.The results revealed that the TNPC-GPTMS/TiO₂ photocatalyst showed much higher photodegradation efficiency than pure TiO₂ and GPTMS/TiO₂,and importantly 0.004 wt%TNPC-GPTMS/TiO₂shows the highest photocatalytic active under the same condition.In addition,the repetition test demonstrated that the TNPC-GPTMS/TiO₂ still maintained high photocatalytic activity over three recycles.Finally,the photocatalytic mechanism was proposed.2.Visible photocatalytic degradation of rhodamine B by composite materials of metal-free and cobalt corrole-TiO₂Six new corroles M[Cor?RO-Ph?_3-n?Ph?_n]?M=H₃,Co,n=0-2,R=COOCH₃Ph?were synthesized and impregnated on the surface of TiO₂,forming new composite materials M[Cor?RO-Ph?_3-n?Ph?_n]-TiO₂.These new composite photocatalysts were characterized by XRD,FT-IR and SEM and all exhibited spherical nanostructures.XRD profiles observed for metal-free and cobalt corrole modified TiO₂ were agreed well with that of the pure TiO₂.Their photocatalytic performances were investigated by testing the photodegradation of rhodamine B?RhB?in aqueous solution under visible light irradiation.Under the visible light after 4 h,the photodegradation efficiency for TiO₂ is 53.8%.Under the same condition,H₃[Cor?RO-Ph?_3-n?Ph?_n]-TiO₂and Co[Cor?RO-Ph?_3-n?Ph?_n]-TiO₂ can increase the yield of photodegrade RhB to86.6%and 90.7%,respectively.The photodegradation efficiency obeyed the following rules:Co[Cor?RO-Ph?_3-n?Ph?_n]-TiO₂>H₃[Cor?RO-Ph?_3-n?Ph?_n]-TiO₂>TiO₂.The results here indicated that both metal-free and cobalt corrole modified TiO₂photocatalysts displayed superior photocatalytic activity and good stability for organic pollutant photodegragation.A possible mechanism of these higher photocatalytic efficiencies was proposed based on the relative experiments.