Enhancing visible-light-activity of Ti-based MOFs based on extending the conjugated degree of organic ligands and photocatalytic degradation process and mechanism in real industrial textile wastewaters

In the manuscript, we developed a novel strategy to effectively improve the visible light absorption of Ti-based MOF by extending the conjugated degree of organic ligands in Ti-based MOFs. The freebased 5,10,15,20-tetraphenylporphyrin (H2TCPP) as organic linkers was used to facilely synthesize Ti-based MOFs (Ti-TiTCPP MOFs). The structural, morphologic and optical properties of Ti-TiTCPP MOFs were investigated. Ti-TiTCPP MOFs was applied to photocatalytic degradation of rhodamine B(RhB) and the photocatalytic degradation performances of Ti-TiTCPP MOFs were compared with that of NH2-MIL-125(Ti) MOFs under mercury lamp, xenon lamp and daylight lamp irradiation, respectively. The results showed the photocatalytic degradation performances of Ti-TiTCPP MOFs are superior to that of NH2-MIL-125(Ti) MOFs in visible region. Furthermore, the photocatalytic degradation mechanism of Ti-TiTCPP MOFs was investigated in detail based on the electrochemical and photoelectrochemical results associated with previously reported photocatalytic degradation mechanisms of NH2-MIL-125(Ti). The possible electrochemical and photoelectrochemical reactions and the changes of Gibbs free energy were analyzed. The degradation possible pathways of RhB and the emerging main intermediate contaminants were carefully analyzed by HPLC-HRMS under the present different solution parameters. And then the photocatalytic system based on Ti-TiTCPP MOFs was successfully applied to deal with real industrial textile wastewaters.