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Two novel covalent triazine polymers were successfully synthesized and applied for simultaneous photocatalytic Cr(VI) reduction and dyes degradation in water without the presence of any sacrificial agents, oxidizer or assisted acid. [Display omitted] • Two novel CTPs were successfully prepared as an efficient photocatalyst for Cr(VI) reduction in water. • The unique D-A structure of the CTPs accelerates the charge separation efficiency. • The photogenerated electrons and ensuing active radicals play important roles in the catalytic process of Cr(VI) reduction. • The design of these CTPs provides a new strategy for constructing functional CTF materials. Two new donor–acceptor covalent triazine polymers (CTPs), namely Th-Trz (JOU-6) and Th-Ph-Trz (JOU-7), containing electron-donating thieno[2,3-b]thiophene (Th) units and electron-withdrawing triazine (Trz) units have been successfully constructed (Ph = benzene ring). The unique conjugated structure of the CTPs invokes wide absorption range and high charge transfer efficiency. Because of these advantages, the as-prepared CTPs are highly effective photocatalysts for Cr(VI) reduction. It is found that high acid concentration in the photocatalytic system may assist the protonation of triazine groups in CTPs, which not only can enhance their adsorption ability for Cr 2 O 7 2−, but also can promote their charge transfer ability. Another important finding is that compared with JOU-6 , JOU-7 shows more efficient charge separation owing to the introduction of benzene ring between the donor and acceptor units, inducing a spatial separation of photogenerated electrons and holes, and thereby giving a better photocatalytic performance. The spatial charge distribution of the CTPs was also investigated by theoretical calculation based on molecular orbital theory. Fascinatingly, Cr(VI) and organic pollutions can be simultaneously removed by JOU-7 without any sacrificial agents, oxidizer, or acid. This work provides a valuable strategy for the design and construction of effective photocatalysts for the removal of pollutants in wastewater. [ABSTRACT FROM AUTHOR]

Conjugated organic polymers (COPs) have attracted increasing attentions as promising metal-free photocatalysts in the past decade. In this work, two newly designed COPs (An-TATB and An-TPA; An ​= ​anthracene, TATB ​= ​1,3,5-triazine-2,4,6-Triphenyl, TPA ​= ​triphenylamine) were solvothermally synthesized. The conjugated structures of the constructed COPs endow them wide absorption ranges and sufficient photoredox potentials. Then, these constructed COPs are developed as photocatalysts for Cr(VI) reduction and organic pollution degradation in water. Due to the unique donor-acceptor structure, An-TATB showed more efficient photoinduced charge separation and better photocatalytic performances than An-TPA. Importantly, Cr(VI) and organic pollution can be simultaneously removed by An-TATB without any sacrificial agent, oxidant or additional acid. In addition, the reaction active species in pollutant removal process have been studied and the photocatalytic mechanism has also been proposed. This work provides an effective way for the design and construction of new high-efficiency metal-free photocatalysts for wastewater treatment. A newly designed conjugated organic polymer with donor-acceptor skeleton were prepared and developed as an efficient photocatalyst for reducing Cr(VI) and degrading organic pollution in water. [Display omitted] • Two novel conjugated organic polymers were successfully designed as photocatalysts. • An-TATB showed good photocatalytic performances by virtue of its unique donor-acceptor structure. • Cr(VI) and organic pollution can be simultaneously removed by An-TATB without any sacrificial agent, oxidant or acid. • This work provides an effective way for the construction of high-efficiency metal-free photocatalysts. [ABSTRACT FROM AUTHOR]

Although iron-based metal-organic frameworks (Fe-MOFs) have displayed the photocatalytic activity, there is still abundant room for improving their photocatalytic performance through tuning the structures. In this work, four novel iron-based metal-organic frameworks (Fe-MOFs) were successfully synthesized via ligand modulation for better photocatalytic Cr(VI) reduction, in which MTBDC-TPT-Fe had the highest catalytic activity (MTBDC = 2,5-bis(methylthio)terephthalic acid, TPT = 2,4,6-tri(4-pyridyl)− 1,3,5-triazine). The boosted photocatalytic reduction may be mainly ascribed to the enhanced electron push-pull effect between iron-oxygen clusters and organic ligands. The introduction of -SCH 3 groups can enhance the light absorption and donate electrons to iron center under visible-light irradiation, meanwhile the separation and transfer of photogenerated charge carriers can be enhanced resulting from the electron-pulling effect when introducing TPT. Moreover, enhanced specific surface areas and positive skeleton charge due to the introduction of TPT may improve active sites exposure and Cr(VI) adsorption, thereby enhancing photocatalytic Cr(VI) reduction activity without the presence of any assisted scavengers. In addition, the photocatalytic mechanism (i.e. active species) were also studied and presented. This work confirmed an effective structure-performance regulation strategy on Fe-MOFs for photocatalytic Cr(VI) reduction. [Display omitted] • Four novel Fe-MOFs are constructed by ligand modulation for superb photocatalytic Cr(VI) reduction. • The introduction of -SCH 3 group can significantly improve the light absorption ability of Fe-MOF. • TPT ligand can improve the separation and migration of charge carriers through electron-pulling effect. • Larger pores and more positive skeleton formed by TPT introduction are favorable for the adsorption of Cr(VI) substrate. • The e-, ·OH radicals, and O 2 ·- radicals are main active species in the Cr(VI) reduction process. [ABSTRACT FROM AUTHOR]