Metal-Organic Framework Templated Z-Scheme ZnIn2S4/Bi2S3 Hierarchical Heterojunction for Photocatalytic H2O2 Production from Wastewater.

Metal-organic framework derived materials received a lot of attention due to their significant benefits in photocatalytic reactions. In this work, a Z-scheme ZnIn2S4/Bi2S3 hierarchical heterojunction is first developed by a one-pot method using CAU-17 as a template. The specific preparation method endows an intimate interface contact between these two monomers, and CAU-17-derived Bi2S3 possesses a high surface area and porosity, resulting in an efficient charge separation and O2 capture. Thus, for photocatalytic H2O2 production from the O2 reduction reaction, the ZnIn2S4/Bi2S3 heterojunction can achieve an H2O2 yield of 995 µmol L-1 in pure water and ambient air under visible light, 4.5 and 4 times that of ZnIn2S4 and Bi2S3, respectively. In addition, in tetracycline solution, ZnIn2S4/Bi2S3 can degrade tetracycline with a degradation rate of 95% by photocatalysis, and at the same time, a final H2O2 production yield of 1223 µmol L-1 is reached. Similarly, high yields of H2O2 are also obtained from wastewater containing o-nitrophenol, acid golden yellow, or acid red, and these pollutants are effectively degraded. This work reveals the potential of metal-organic framework-derived materials in photocatalysis, as well as provides insights into H2O2 green synthesis and wastewater treatment.

Interspersing CdS nanodots into iodine vacancy-rich BiOI sphere for photocatalytic lignin valorization.

Flower-like BiOI was decorated by CdS nanodots and followed by the introduction of iodine vacancies (VI) for photocatalytic sodium lignosulfonate (SLS) valorization under visible light. The iodine vacancies could adjust the band configuration, strengthen the light absorption and act as electron traps, while the intimate contact between BiOI and CdS nanodots provides a high-speed channel for charge transfer. As a consequence, the photocatalytic performance of SLS conversion into value-added vanillin was greatly improved over CdS/BiOI-VI compared with those of CdS, BiOI and CdS/BiOI. The highest yield of vanillin is 10.95 mg/gSLS over CdS/BiOI-VI, about 5, 8.7, 1.3 times those of CdS, BiOI, CdS/BiOI, respectively, and exceeding most related photocatalysts reported elsewhere. More significantly, as to the lignin from Masson pine and alkali lignin, the corresponding vanillin yield can reach 7.04 and 6.54 mg/glignin, respectively, under the same condition, which suggests the great potential and universality for photocatalytic lignin valorization over such CdS/BiOI-VI heterostructure.

Cellulose-Derived Carbon Dot-Guided Growth of ZnIn2 S4 Nanosheets for Photocatalytic Oxidation of 5-Hydroxymethylfurfural into 2,5-Diformylfuran.

Cellulose-derived carbon (CC) dot-directed growth of ZnIn2 S4 was achieved through hydrothermal treatment of carboxylated cellulose followed by in situ growth of ZnIn2 S4 nanosheets. The carbon dots inherited from carboxylated cellulose equip plenty of surface carboxyl groups, which induce the ionic interaction with Zn2+ and In3+ and the guided growth of ZnIn2 S4 . As a result, the nanosheets of ZnIn2 S4 are evenly and intimately grown on the small carbon dots, providing high-speed channels for charges transfer. In conjunction with the reinforced visible-light capture and good conductivity of carbon dots, the resultant CC/ZnIn2 S4 shows an outstanding photocatalytic activity. As a proof-of-concept, visible-light-driven 5-hydroxymethylfurfural oxidation into 2,5-diformylfuran was conducted. The evolution of 2,5-diformylfuran over the optimal CC/ZnIn2 S4 sample can reach ∼2980 µmol g-1 , about 3.4 times that of pristine ZnIn2 S4 . Additionally, the apparent quantum yield could attain 3.4 % at a wavelength of 400 nm.

Amino-functionalized Ti-metal-organic framework decorated BiOI sphere for simultaneous elimination of Cr(VI) and tetracycline.

A subtle flower-like MIL-125-NH2@BiOI was fabricated by a facile solvothermal method for simultaneously eliminating Cr(VI)/tetracycline mixed pollutants under visible light. The strong interaction between amino in MIL-125-NH2 and Bi3+ of BiOI promotes the formation of this unique inlaid structure and enables the favorable contact between MIL-125-NH2 and BiOI, thus accelerating the transfer of charge carriers. Remarkably, MIL-125-NH2@BiOI displays a superior activity compared with that of two monomers for the photocatalytic reduction of Cr(VI) and degradation of tetracycline. More significantly, the photocatalytic efficiency can be further boosted in the coexistence of Cr(VI) and tetracycline, which is 1.8 and 1.6 times that of single Cr(VI) and tetracycline, respectively. The synergistic effect between Cr(VI) reduction and tetracycline oxidative degradation can further facilitate the separation of photo-induced electrons and holes, resulting in the improved efficiencies in the Cr(VI)/tetracycline coexistent environment. This work sheds light on that MOF-based photocatalysts possess huge potential for practical environmental remediation.

Inlaying metal-organic framework derived pancake-like TiO2 into three-dimensional BiOI for visible-light-driven generation of vanillin from sodium lignosulfonate.

Pancake-like TiO2 (M-TiO2) derived from the metal-organic framework was inlaid into three-dimensional flower-like BiOI through a facile solvothermal method. M-TiO2 supplies large surface area and mesoporous structure for attachment and transfer of the substrates and products, while BiOI acts as a photosensitizer to absorb visible light and generates electrons and holes. The distinct structure of M-TiO2/BiOI gives a favorable contact between the two monomers, and promotes the transfer of charge carriers. In conjunction with the proper band positions of M-TiO2 and BiOI, the efficient separation of electron-hole pairs is attained. Benefiting from the above cooperative effects of M-TiO2 and BiOI, the performance for the vanillin generation from sodium lignosulfonate (SLS) over M-TiO2/BiOI composites has a prominent improvement under visible light. Specifically, the yield over optimal M-TiO2/BiOI sample is about 5.8 mg/gSLS, obviously superior to that over pristine M-TiO2 (~1 mg/gSLS) and BiOI (~1.1 mg/gSLS). It is found that h+ and O2- play the key role for vanillin generation from sodium lignosulfonate, and the low vanillin generation under UV-vis light sheds light on that OH is an adverse factor. We hoped that this work could inspire the studies on the photocatalytic valorization of biomass using noble metal-free catalysts.