Controlling the coordination environment of Co atoms derived from Co/ZIF-8 for boosting photocatalytic H2 evolution of CdS

Cobalt metal replaces Co-ZIF-8 mesoporous material for effective adsorption of arsenic from wastewater

The high cost and low adsorption capacity of primary metal-organic frameworks (ZIF-8) limit their application in heavy metal removal. In this paper, Co/Zn bimetallic MOF materials were synthesized with excellent adsorption performance for As5+. The adsorption reached equilibrium after 180 min and the maximum adsorption was 250.088 mg/g. In addition, Co-ZIF-8 showed strong selective adsorption of As5+. The adsorption process model of Co-ZIF-8 fits well with the pseudo-second-order kinetic model (R2=0.997) and Langmuir isotherm model (R2=0.994), and it is demonstrated that the adsorption behavior of the adsorbent is a single layer of chemical adsorption. In addition, when the adsorbent enters the arsenic-containing solution, the surface of Co-ZIF-8 is hydrolyzed to produce a large number of Co-OH active sites, and As5+ arrives at the surface of Co-ZIF-8 by electrostatic adsorption and combines with the active sites to generate the arsenic-containing complex As-O-Co. After four cycles, Co-ZIF-8 showed 80% adsorption of As5+. This study not only provides a new method to capture As5+ in water by preparing MOF with partial replacement of the central metal, but also has great significance for the harmless disposal of polluted water.

Photocatalytic degradation of chlorinated organic pollutants by ZnS@ZIF-8 composite through hydrogen peroxide generation by activating dioxygen under simulated sunlight irradiation

Photocatalytic hydrogen peroxide (H2O2) production and its application in advanced oxidation processes (AOPs) are regarded as low-cost and environmentally friendly wastewater treatment processes. Herein, by modifying a small amount of sulphide on the zeolitic imidazolate framework-8 (ZIF-8), a ZnS@ZIF-8 composite and used for photocatalytic H2O2 production to degrade chlorinated organic pollutants under simulated sunlight (SSL). ZnS@ZIF-8 composite could enhance the separation of photo-induced charge carriers, promote electron transfer from zinc sulphide (ZnS) to ZIF-8, which exhibited good selectivity for the two-electron oxygen reduction reaction (2e--ORR) and two-electron water oxidation (2e--WOR) pathways. Based on oxygen (O2) activation, the developed ZnS@ZIF-8/O2/SSL system could achieve 6.43 mmol/L H2O2 production within 150 min, which was approximately 8.66 and 10.36 times higher than that of the ZnS/O2/SSL and ZIF-8/O2/SSL systems, respectively. In the ZnS@ZIF-8/O2/SSL system, the ORR, WOR and H2O2 photolysis led to the generation of hydroxyl radical (•OH), while the photochemical behavior of ZnS in ZnS@ZIF-8 composite resulted in the generation of active hydrogen (*H). Benefitting from the high concentration of H2O2 and the coexistence of redox species in the ZnS@ZIF-8/O2/SSL system, various chlorinated organic pollutants could be dechlorinated and mineralized. In addition, a possible mechanism for photocatalytic H2O2 production was also proposed. Importantly, the proposed process did not involve an additional sacrificial agent or Fenton-like catalysts. This work provides insights into the potential application of ZnS@ZIF-8 composite for H2O2 production and wastewater treatment.

In Situ Growth of CdZnS Nanoparticles@Ti3C2Tx MXene Nanosheet Heterojunctions for Boosted Visible-Light-Driven Photocatalytic Hydrogen Evolution

Using natural light energy to convert water into hydrogen is of great significance to solving energy shortages and environmental pollution. Due to the rapid recombination of photogenerated carriers after separation, the efficiency of photocatalytic hydrogen production using photocatalysts is usually very low. Here, efficient CdZnS nanoparticles@Ti3C2Tx MXene nanosheet heterojunction photocatalysts have been successfully prepared by a facile in situ growth strategy. Since the CdZnS nanoparticles uniformly covered the Ti3C2Tx Mxene nanosheets, the agglomeration phenomenon of CdZnS nanoparticles could be effectively inhibited, accompanied by increased Schottky barrier sites and an enhanced migration rate of photogenerated carriers. The utilization efficiency of light energy can be improved by inhibiting the recombination of photogenerated electron-hole pairs. As a result, under the visible-light-driven photocatalytic experiments, this composite achieved a high hydrogen evolution rate of 47.1 mmol h-1 g-1, which is much higher than pristine CdZnS and Mxene. The boosted photocatalytic performances can be attributed to the formed heterojunction of CdZnS nanoparticles and Ti3C2Tx MXene nanosheets, as well as the weakened agglomeration effects.

Janus Z-scheme heterostructure of ZnIn2S4/MoSe2/In2Se3 for efficient photocatalytic hydrogen evolution

Artificial manipulation of charge separation and transfer are central issues dominating hydrogen evolution reaction triggered via photocatalysis. Herein, through elaborate designing on the architecture, band alignment, and interface bonding mode, a sulfur vacancy-rich ZnIn₂S₄-based (Vs-ZIS) multivariate heterostructure ZnIn₂S₄/MoSe₂/In₂Se₃ (Vs-ZIS/MoSe₂/In₂Se₃) with specific Janus Z-scheme charge transfer mechanism is constructed through a two-step hydrothermal process. Steering by the Janus Z-scheme charge transfer mechanism, photogenerated electrons in the conduction band of MoSe₂ transfer synchronously to the valence band of Vs-ZIS and In₂Se₃, resulting in abundant highly-active photogenerated electrons reserved in the conduction band of Vs-ZIS and In₂Se₃, therefore significantly enhancing the photocatalytic activity of hydrogen evolution. Under visible light irradiation, the optimized Vs-ZIS/MoSe₂/In₂Se₃ with the mass ratio of MoSe₂ and In₂Se₃ to ZnIn₂S₄ at 3 % and 30 %, respectively, performs a high hydrogen evolution rate of 124.42 mmol·g^-1·h^-1, about 43.5-folds of the original ZIS photocatalyst. Besides, an apparent quantum efficiency (AQE) of 22.5 % at 420 nm and favorable durability are also achieved over Vs-ZIS/MoSe₂/In₂Se₃ photocatalyst. This work represents an important development in efficient photocatalysts and donates a sound foundation for the design of regulating charge transfer pathways.

MOFs and MOF-Derived Materials for Antibacterial Application

Bacterial infections pose a serious threat to people's health. Efforts are being made to develop antibacterial agents that can inhibit bacterial growth, prevent biofilm formation, and kill bacteria. In recent years, materials based on metal organic frameworks (MOFs) have attracted significant attention for various antibacterial applications due to their high specific surface area, high enzyme-like activity, and continuous release of metal ions. This paper reviews the recent progress of MOFs as antibacterial agents, focusing on preparation methods, fundamental antibacterial mechanisms, and strategies to enhance their antibacterial effects. Finally, several prospects related to MOFs for antibacterial application are proposed, aiming to provide possible research directions in this field.

Reconstruction of bimetal CoFe0.13-MOF to enhance the catalytic performance in the oxygen evolution reaction

Oxygen evolution reaction (OER) is a key process in electrochemical energy conversion systems. This paper found that the solvothermal reconstruction could resume the original morphology and generate more oxygen vacancies on the surface of oxyhydroxide. The reconstructed electrocatalyst (re-CoFe_0.13O_xH_y) presents promising long-term stability (>85 h) under 1 M KOH condition without replacing the electrolyte.

Fabrication of visible-light response cadmium sulfide modified superhydrophobic surface for water resource remediation

Widespread concern has been attached to the frequent occurrence of pollution by oil slicks and water-soluble pollutants in recent years. The semiconductor photocatalysis is applied to sewage treatment owing to the advantages of energy-conserving and environmental protection. However, its application is limited by the defects of not solving oil slicks and the hard recyclability. In this paper, the high specific surface area and rod-shaped CdS were prepared using template and alkali-treated methods. Next, the alkylated SiO₂and alkali-treated CdS were deposited on pure fabric by physical deposition to prepare the multifunctional superhydrophobic fabric. The specific surface area and morphology of alkali-treated CdS were tested by BET specific surface area test and field emission scanning electron microscope. Besides, oil/water separation, water contact angle, and stability test experiments were performed to determine the superhydrophobic performance. Photocatalysis degradation efficiency and cycle degradation stability of multifunctional fabric were characterized by photocatalysis degradation Rh B experiment. Consequently, the alkali-treated CdS displays a high specific surface up to 343 m²g^-1. The multifunctional fabric presents excellent superhydrophobic performance with the water contact angle up to 155°. Meanwhile, the water contact angle of multifunctional fabric is always over 150° under various circumstances (acid-base corrosion, soaking time at 100 °C and frictional numbers), indicating that the multifunctional fabric has excellent superhydrophobic stability. Moreover, the fabric also exhibits outstanding photocatalysis performance (the degradation efficiency is 94% after 3 cycles). Our work provides a feasible method for addressing oil slicks on water surface and degrading water-soluble pollutants with extensive application prospects in water resource remediation.