Metal-Organic Frameworks With Variable Valence Metal-Photoactive Components: Emerging Platform for Volatile Organic Compounds Photocatalytic Degradation

Recent Advances in Metal-Organic Framework (MOF)-Based Photocatalysts: Design Strategies and Applications in Heavy Metal Control

The heavy metal contamination of water systems has become a major environmental concern worldwide. Photocatalysis using metal-organic frameworks (MOFs) has emerged as a promising approach for heavy metal remediation, owing to the ability of MOFs to fully degrade contaminants through redox reactions that are driven by photogenerated charge carriers. This review provides a comprehensive analysis of recent developments in MOF-based photocatalysts for removing and decontaminating heavy metals from water. The tunable nature of MOFs allows the rational design of composition and features to enhance light harvesting, charge separation, pollutant absorptivity, and photocatalytic activities. Key strategies employed include metal coordination tuning, organic ligand functionalization, heteroatom doping, plasmonic nanoparticle incorporation, defect engineering, and morphology control. The mechanisms involved in the interactions between MOF photocatalysts and heavy metal contaminants are discussed, including light absorption, charge carrier separation, metal ion adsorption, and photocatalytic redox reactions. The review highlights diverse applications of MOF photocatalysts in treating heavy metals such as lead, mercury, chromium, cadmium, silver, arsenic, nickel, etc. in water remediation. Kinetic modeling provides vital insights into the complex interplay between coupled processes such as adsorption and photocatalytic degradation that influence treatment efficiency. Life cycle assessment (LCA) is also crucial for evaluating the sustainability of MOF-based technologies. By elucidating the latest advances, current challenges, and future opportunities, this review provides insights into the potential of MOF-based photocatalysts as a sustainable technology for addressing the critical issue of heavy metal pollution in water systems. Ongoing efforts are needed to address the issues of stability, recyclability, scalable synthesis, and practical reactor engineering.

Ferric-ellagate complex: A promising multifunctional photocatalyst

The semiconductors have exhibited great potential in the field of photocatalytic energy production, environmental remediation and bactericidal. Nevertheless, those inorganic semiconductors are still restricted in commercial application due to the drawbacks of easy agglomeration and low solar energy conversion efficiency. Herein, ellagic acid (EA) based metal-organic complexes (MOCs) were synthesized through a facile stirring process at room temperature with Fe³⁺, Bi³⁺ and Ce³⁺ as the metal center. The EA-Fe photocatalyst exhibited superior photocatalytic activity toward Cr(VI) reduction, where Cr(VI) were completely removed within 20 min. Meanwhile, EA-Fe also displayed good photocatalytic degradation of organic contaminants and photocatalytic bactericidal performance. The photodegradation rates of TC and RhB by EA-Fe were 15 and 5 times that by bare EA, respectively. Moreover, EA-Fe was capable of effectively eliminating both E. coli and S. aureus bacteria. It was found that EA-Fe was capable of generating superoxide radicals, which could participate in the reduction of heavy metals, degradation of organic contaminants and inactivation of bacteria. A photocatalysis-self-Fenton system could be established by EA-Fe solely. This work would provide a new insight for designing multifunctional MOCs with high photocatalytic efficiency.

Advances in Hybrid Composites for Photocatalytic Applications: A Review

Heterogeneous photocatalysts have garnered extensive attention as a sustainable way for environmental remediation and energy storage process. Water splitting, solar energy conversion, and pollutant degradation are examples of nowadays applications where semiconductor-based photocatalysts represent a potentially disruptive technology. The exploitation of solar radiation for photocatalysis could generate a strong impact by decreasing the energy demand and simultaneously mitigating the impact of anthropogenic pollutants. However, most of the actual photocatalysts work only on energy radiation in the Near-UV region (<400 nm), and the studies and development of new photocatalysts with high efficiency in the visible range of the spectrum are required. In this regard, hybrid organic/inorganic photocatalysts have emerged as highly potential materials to drastically improve visible photocatalytic efficiency. In this review, we will analyze the state-of-art and the developments of hybrid photocatalysts for energy storage and energy conversion process as well as their application in pollutant degradation and water treatments.

Recent Advances in Vehicle Exhaust Treatment with Photocatalytic Technology

Vehicle exhaust has been acknowledged as an essential factor affecting human health due to the extensive use of cars. Its main components include volatile organic compounds (VOCs) and nitrogen oxides (NOx), which can cause acute irritation and chronic diseases, and significant research on the treatment of vehicle exhaust has received increasing attention in recent decades. Recently, photocatalytic technology has been considered a practical approach for eliminating vehicle emissions. This review highlights the crucial role of photocatalytic technology in eliminating vehicle emissions using semiconductor catalysts. A particular emphasis has been placed on various photocatalytic materials, such as TiO2-based materials, Bi-based materials, and Metal–Organic Frameworks (MOFs), and their recent advances in the performance of VOC and NOx photodegradation. In addition, the applications of photocatalytic technology for the elimination of vehicle exhaust are presented (including photocatalysts combined with pavement surfaces, making photocatalysts into architectural coatings and photoreactors), which will offer a promising strategy for photocatalytic technology to remove vehicle exhaust.

Advancements in visible light responsive MOF composites for photocatalytic decontamination of textile wastewater: A review

Heterogeneous photocatalysis using metal-organic frameworks (MOFs) is expected to provide a pivotal solution for the remediation of toxic dyes and heavy metals from textile wastewater. However, MOFs often suffer from a low removal efficiency, due to the rapid recombination between holes and electrons, generated upon photoexcitation. Additionally, the MOFs exhibit poor water stability, which restricts their large-scale application. In this regard, various approaches (i.e. doping of metal nanoparticle, semiconductor, quantum dot, and ligand functionalization) have been adopted for the formation of multifunctional composites. The MOF-composites possess suitable photochemical, surface, optical, and electronic properties, resulting in enhanced water stability, visible light absorption, and reduced recombination between photogenerated species. This comprehensive review targets to provide an insight into the synthesis and subsequent application of various MOF composites for photocatalytic removal of organic contaminants (dyes) and inorganic (Cr(VI)) contaminants from water. MOFs/graphene oxide composites possess improved surface area and reusability whereas noble metal incorporated MOFs composites suffer from photocorrosion and are relatively costly. Zr and Ti based MOFs exhibit tuning from UV to visible light response and surpass the poor water stability upon binary/ternary composite formation. The role of the dopants in enhancing the efficiency of the composites; the effect of influencing factors such as solution pH, pollutant concentration; the mechanism, and the kinetics of reactions have been outlined. In spite of many advancements, the article also summarizes some roadblocks that need to be unraveled to achieve the energy-water-environment nexus and scope for future breakthrough research in this field.