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• Tuning band structures based on metal sulfides/Zr-MOF heterojunctions. • Greatly optimized band structures. • Significantly improved light energy utilization and optical-electronic properties. • Remarkably enhanced photocatalytic efficiencies and accelerated reaction kinetics. Assembly of advanced MOFs based heterojunctions is an effective avenue to facilitate light utility and photogenerated electron-hole separation for photochemical detoxification of Cr(VI) and degradation of reactive dyes. Systematically polishing the band states of photocatalysts is the crucial point but still requires further study. Herein, a band structure tuning strategy was designed by depositing carefully selected metal sulfides on a 2D Zr-MOF to assemble six metal sulfides/Zr-MOF heterojunctions. Fortunately, In 2 S 3 /Zr-MOF presents prominent optical-electronic properties and photocatalytic performances since the highly matched band structure. And its UV–Visible light utility, carriers migration rate, electron-hole separation efficiency and recombination inhibition ability have been greatly optimized. Ingeniously, In 2 S 3 /Zr-MOF (M5) exhibits best photochemical purification abilities towards ultra-stubborn reactive dyes RR11, RB21 and highly toxic Cr(VI) ions, under 500 W xenon lamp, with degradation/reduction efficiencies of 91.8, 93.3 % and 97.9 % within 5, 13 h and 70 min, respectively. Compared with pure In 2 S 3 and Zr-MOF, the photocatalytic degradation kinetics towards RR11 have been increased 27.18 and 38.50 times, respectively, providing the recyclability of more than 4 times. Mechanism studies confirm that ·O 2 − species play dominant roles in removal of reactive dyes, and the powerful electrons transfer from the conduction band (CB) of In 2 S 3 to Zr-MOF's relatively positive CB further reinforce their ability to combine with dissolved O 2 in water to provide more ·O 2 −. While the cooperation of electrons in CB of Zr-MOF with O 2 /·O 2 − has been suggested as the mechanism for photocatalytic detoxification of Cr(VI) to Cr(III). This study provides a feasible strategy for boosting the photochemical purification capacities of Zr-MOFs based heterojunction platforms. A band structure tuning strategy has been effectively designed and carried out by depositing diverse metal sulfides with unique band states on a 2D Zr-MOF, respectively, enabling precisely modulate the optical-electronic properties and boost the photocatalytic reduction and degradation efficiencies under xenon lamp. [Display omitted] [ABSTRACT FROM AUTHOR]

Dichromates and dyes have been widely used in industrial and agricultural production, but they are also responsible for the deterioration of water environments. Photochemical purification of them based on MOFs based photocatalysts has been proven to be feasible. And construction of MOFs based heterojunctions to polish the band states is an effective method for enhancing the separation of photogenerated electron-hole separation and carriers migration under low energy light. Herein, a Zr(IV)-biquinoline framework with bcu topology was synthesized to act as a matrix for depositing the in-situ generated In 2 S 3 species, providing a novel In 2 S 3 /Zr-MOF heterojunction. Indeed, owing to the highly matched band structure of the two components, the new heterojunction exhibits optimized visible light utility, photogenerated electron-hole recombination inhibition ability and carriers migration kinetics. Ingeniously, the 10%-Zr-MOF exhibited excellent photocatalytic REDOX abilities against Cr(VI) ions and dye RhB, with the photocatalytic deoxidation efficiency towards Cr(VI) ions (96.7 %) has been confirmed to be 3.14 and 1.42 times that of pristine Zr-MOF (30.8 %) and sole In 2 S 3 (68.2 %), respectively. Moreover, it also displayed a photocatalytic reduction kinetic rate of 0.031 min−1, which is 11.3 times and 2.69 times higher than that of fresh Zr-MOF (0.00274 min−1) and pure In 2 S 3 (0.0115 min−1). And the photocatalytic reduction and degradation mechanisms of In 2 S 3 /Zr-MOF also have been deliberately proposed, according to the detailed experimental and instrumental characterization results. This contribution presents a feasible post-modification reinforcement strategy to assemble novel Zr-MOFs based photocatalytic platforms for the decontamination of Cr(VI) and dyes from water. Greatly optimized band states, low energy light energy utilization, optical-electronic properties and decontamination of Cr(VI) and RhB were achieved via a novel In 2 S 3 /Zr-MOF heterojunction. Its photocatalytic deoxidation efficiency towards Cr(VI) is 3.14 and 1.42 times of pristine Zr-MOF and pure In 2 S 3 , respectively. [Display omitted] • Band structures modulating based on metal sulfides/Zr-MOF heterojunction. • Greatly optimized band states. • Significantly improved light energy utilization and optical-electronic properties. • Remarkably enhanced photocatalytic efficiencies and accelerated reaction kinetics. [ABSTRACT FROM AUTHOR]

• Photosensitive post-modification based on the super-stable UiO-67. • Greatly narrowed band gap and optimized band structure. • Significantly improved visible light utilization and optical-electronic properties. • Remarkably enhanced photocatalytic efficiencies and accelerated reaction kinetics. As a new kind of organic-inorganic hybrid semiconductor materials, MOFs have come into focus as photocatalysts for decontamination of Cr(VI) oxates and reactive dyes from contaminated water. However, although most Zr-MOFs exhibit hydrolytic stability, they absorb almost only ultraviolet light. Assembly of MOFs with both hydrolytic stability and high visible light responsiveness thus has become a most feasible avenue recently. Here, composite of Ag@UiO-67 was intentionally designed by modifying the classical Zr-MOF of UiO-67 with highly photosensitive Ag+ ions. Results suggested that compared with pristine UiO-67, Ag@UiO-67 displays significantly narrowed band gap (Eg) value, sufficiently negative conduction band (CB) potential, suitable valence band (VB) potential and significantly improved charge transfer efficiency. Notably, the Eg value of 2.09 eV gives Ag@UiO-67 excellent ability of visible photocatalytic reduction of Cr(VI) and degradation of Reactive dark blue K-R (RB13), with reduction and degradation efficiencies of 91.37 % within 140 min (k = 0.024 min−1) and 92.63 % within 160 min (k = 0.016 min−1), respectively, which are 5.6 and 6.9 times of as synthesized UiO-67. Moreover, photocatalytic mechanism studies reveal that · O 2 – plays key roles in bleaching RB13 and photogenerated species with sufficient negative potential can effectively reduce Cr(VI). And Ag@UiO-67 can utilize visible light more efficiently to accelerate the charge transfer rate. This work provides a feasible avenue to tailor the visible light sensitivity and band structure of classic Zr-MOFs, for eliminating inorganic and organic contaminants such as Cr(VI) ions and dye of RB13. Visible photocatalytic reduction and degradation capacities towards Cr(VI) and reactive dye (RB13) have been successfully achieved, by firmly anchoring Ag+ ions in UiO-67. This study provides a feasible strategy to realize the low-energy light utilization and bifunctionality of robust Zr-MOFs platforms. [Display omitted] [ABSTRACT FROM AUTHOR]

Lead and chromate/dichromate are widely used in manufacturing industry, but Pb(II) and Cr(VI) ions pose fatal threats to human health and the water ecological environment. It is thus highly desirable to develop novel and valid strategies for rapid detection and effective decontamination of these heavy metal ions. Design and assembly of luminescent Metal-Organic Framework (LMOFs) for effective recognition and removal of Pb(II) and/or Cr(VI) from water provide a feasible avenue to address this issue. Herein, a novel Cd(II)-MOF, [(Cd 3 L 2)]·(solvent) x (labeled as compound 1) with bright blue fluorescence was assembled under the solvothermal reaction of triangular ligand 5'-(5-carboxy-1H-benzo [ d ]imidazole-2-yl)-[1,1':3′,1″-terphenyl]-4,4″-dicarboxylic acid (H 3 L) and Cd(NO 3) 2. Given that the unique structure features of 3D stacking framework, i. e. strong π···π conjugative effects of organic linkers, plentiful free imidazole N atoms and carboxyl O atoms, Cd-MOF of 1 was deliberately deployed as bifunctional platform to sense Pb(II)/Cr(VI) and photochemically reduce Cr(VI) to Cr(III). Notably, 1 emits durable bright blue fluorescence and performs rapid quenching sense for Pb2+, Cr 2 O 7 2− and CrO 4 2−, with ultra low detection limits of 1.89, 4.83 and 2.84 ​ppb, respectively. Moreover, highly toxic Cr(VI) could be rapidly and thoroughly reduced to Cr(III) ions by 1 under the irradiation of mercury lamp, with reliable recycling ability. The possible photoluminescence, quenching and photocatalytic reduction mechanisms also were tentatively proposed. Highly efficient and bifunctional for cationic Pb(II), anionic Cr(VI) analytes detection and Cr(VI) photochemical reduction decontamination were thoroughly demonstrated by a powerful Cd(II)-Organic Framework platform, performing fairly low detection limits values and rather high/rapid photocatalytic reduction capability. And may open a new avenue for addressing the fatal environmental pollution issues caused by heavy metal ions. [Display omitted] • The unique dual-fluorescent probe for cationic Pb(II) and anionic Cr(VI) analytes. • Fairly low detection limits values among all reported MOF-based sensors. • Excellent selectivity, anti-interference abilities and reliable recyclability. • High efficiency, rapid and recyclable photocatalytic reduction abilities for Cr(VI). [ABSTRACT FROM AUTHOR]