CO2 conversion to value-added fuels and chemicals under photocatalytic conversion is a sustainable solution towards reducing the increasing carbon emission in the atmosphere as well as aiding in clean energy production. Metal organic frameworks (MOFs), which are comprised of transition-metal nodes and multifunctional organic linkers have been found to be highly promising photocatalysts in CO2 reduction as they have a high surface area, structural, and CO2 adsorption capacity. Their photoresponsive property, caused by the transfer of the ligand-to-metal charge, or metal-oxo cluster excitation permits the effective generation and separation of charge carriers, necessary to drive multi-electron reduction reactions of CO2. This review offers a detailed description of the state-of-the-art MOF-based systems on the photoreduction of CO2 to major products of CH4, CH3OH, HCOOH, and CO. Specific attention is paid to the functionalization of linkers, deposition of metal nanoparticles, heterojunction, and co-catalysts engineering, which have a considerable impact on increasing its activity and selectivity of products. The mechanistic knowledge behind charge transfer, intermediate stabilization, and adsorption phenomena are explained in detail. Besides this, the review demonstrates the prevailing bottlenecks, such as charge recombination, low quantum yields, and poor long-term stability, and how machine learning methods could be used to speed up the prediction and optimization of high-performance MOF photocatalysts. Overall, MOFs still have an enormous potential in solar-based CO2 valorization, but improvements in stability and reactor integration are required before they can be used in practice.

This study investigates the potential of z-scheme heterojunction design of NiO/ZnO-based synthesized by urea-assisted modified hydrothermal method with a reaction temperature of 110 degrees C for 6 h, followed by ultrasonic treatment (for 1 h). XRD pattern confirms the presence of both the phases in the composites. The FESEM images showed that NiO has flower-like structure (with an average thickness of nanosheets similar to 25 nm), while ZnO has nanowire structures (with an average diameter of similar to 43 nm). UV-DRS and Mott-Schottky plot analysis helped to establish the band gap and band positions of NiO and ZnO, further facilitated in understanding the charge transfer mechanism. NiO and ZnO showed photocatalytic degradation efficiency of 60.2 % and 46.5 % respectively towards RR35 dye under UV light in 100 min. NZ11 displayed the best photocatalytic degradation of 98.8 % with a reaction rate (k) of 0.04336 min(-1) and stands out as an excellent material for environmental wastewater treatment through efficient photocatalysis.

The pressing need to enhance the efficiency of wastewater treatment is underscored by the significant threat that water pollution poses to human health and environmental stability. Among current remediation techniques, photocatalysis has emerged as a promising approach due to its reliance on advanced material properties. Cerium oxide’s tunable bandgap and defect engineering, combined with graphene’s high surface area, conductivity, and functionalization, synergistically enhance photocatalytic performance. This makes CeO2-graphene composites highly promising for environmental remediation applications. This review paper systematically examines water pollution challenges and evaluates existing treatment methodologies, with a particular emphasis on CeO2-based photocatalysts modified with graphene and its derivatives, such as graphene oxide (GO) and reduced graphene oxide (rGO). These composites demonstrate potential for superior photocatalytic performance and reactor design. Key issues, including environmental impact, stability, reusability, and compatibility of these materials with evolving technologies, are thoroughly discussed. Additionally, considerations for scaling production and commercializing these composites are addressed, suggesting avenues for future research and industrial applications. This review aims to provide a comprehensive understanding of the synergistic effects of CeO2 and graphene-based materials, opening new possibilities for advanced clean water treatment technologies.

Ternary equiatomic compounds (RTX) are well-known and are of significant interest owing to their extraordinary crystal chemistry and intriguing electronic structure properties. After diving into roughly the 50-year-old history of the superconductivity of these compounds, herein, we are aimed at computationally investigating the superconducting properties of the RTX compound. The higher-member analog of the previously reported MgPtSi superconductor, CaPtSi, is computationally investigated in this study, including its crystal structures, phase transitions, and superconducting properties. CaPtSi is an equiatomic ternary compound that exhibits polymorphism at high pressure. In its ground state at ambient pressure, CaPtSi exists in a cubic LaIrSi-type crystal structure. The cubic phase goes through a structural phase transition at a pressure of 1.4 GPa, transforming into a monoclinic EuNiGe-type structure. The monoclinic phase further transforms into the orthorhombic TiNiSi-type structure at a pressure of 3.5 GPa. We used first-principles density functional theory to investigate the electronic structure, dynamic stability, and superconductivity of CaPtSi polymorphs at pressures ranging from 1 atm to 20 GPa. Our calculations confirm the phase sequence of cubic, monoclinic, and orthorhombic phases with critical pressures of 1.4 and 3.5 GPa, respectively. Moreover, the quenchability of the high-pressure phases reported in previous experiments was confirmed by phonon calculations, which further demonstrated that all three phases are dynamically stable at ambient and high-pressure conditions. The superconducting properties of all stable and metastable structures were investigated using the phonon-mediated mechanism, and the Allen-Dynes modified McMillan equation was used to calculate the superconducting critical temperature (Tc). At ambient pressure, the Tc value for orthorhombic CaPtSi is found to be 2.4 K, with an electron-phonon coupling strength of 0.57. The predicted Tc of orthorhombic CaPtSi is comparable to the previously observed Tc (2.5 K) for orthorhombic MgPtSi in TiNiSi-type structure.

The pursuit of sustainable energy alternatives has intensified the focus on renewable alternatives, particularly hydrogen, owing to its high energy density and environmentally benign combustion. Photocatalytic water splitting, which harnesses sunlight to produce hydrogen, is emerging as a game-changing approach in this area. Among the many materials explored, transition metal dichalcogenides (TMDs), especially tungsten-based materials (W), have captured significant attention for their exceptional photocatalytic properties. This review provides a comprehensive analysis of the recent advancements in the field of W-based photocatalysts for hydrogen production. Subsequently, this review delves into the fundamentals of photocatalytic water splitting and the mechanisms underpinning the hydrogen evolution reaction (HER). The core of the review is dedicated to evaluating the photocatalytic performance of WS2, WSe2, and WTe2 in hydrogen generation. By analyzing the structural, electronic, and catalytic features of these materials, we shed light on their strengths, limitations, and future potential. Finally, we outline the scope and perspectives of this review, aiming to provide insights that could drive future research and development in photocatalysis-assisted hydrogen production technologies.

Removal of organic pollutants by semiconductor photocatalysis is one of the most emanating area of sustainable energy generation that drew emphasis on the development of novel photocatalysts for environmental remediation. In this work, Sillen phases, BaBiO2X (X = Cl & Br), were synthesized by solid-state reaction method. The compounds were characterized by Powder X-ray diffraction (PXRD), Field emission scanning electron microscopy (FE-SEM), Energy dispersive X-ray (EDX), Transmission electron microscopy (TEM), UV-visible diffuse reflectance spectra (UV-Vis DRS), Photoluminescence (PL) and Electrochemical impedance spectroscopy (EIS). Rietveld refinement of BaBiO2Cl and BaBiO2Br evinces that both compounds crystallize in the orthorhombic unit cell of Cmcm space group. Structural analysis reveals the influence of X anion on the electronic properties. Both compounds show absorption in UV region with wide band gaps of 3.1eV and 3.7eV for BaBiO2Cl and BaBiO2Br, respectively. SEM shows plate-like morphology, with compositional homogeneity all over the region. EIS studies signify higher RCT values for BaBiO2Cl as compared to BaBiO2Br. Density functional theory (DFT) studies demonstrate the predominant contribution of O 2p orbitals in the valence band maxima (VBM) of oxyhalides and explains their photo-stability. Photocatalytic activity of these Sillen phases was analyzed by photocatalytic hydrogen generation and degradation of Methyl orange dye under UV light irradiation. Photostability and the reusability studies of photocatalysts reveal excellent stability with reusability. Energy level diagram and scavenger test studies indicate a significant role of center dot OH radicals in the degradation mechanism.

Sillen-Aurivillius (S-A) hybrid layered perovskites constitute an important class of intergrowth compounds that have been recently demonstrated as high-performing semiconductor photocatalysts. The present study reports the synthesis of a series of three-layer S-A perovskites (A3X1 hybrids), Bi(4)AA ' Ti2NbO14Cl (A, A ' = Sr and Ba), by an innovative approach involving interchange of Sr and Ba between the starting Sillen and Aurivillius blocks to examine the cation redistribution in the resulting intergrowth phases. Rietveld structure refinements reveal the preferred occupation of Sr in the perovskite block, while the larger Ba is grounded in the Sillen block. Due to cation migration between the fluorite-like [Bi2O2] layer and the perovskite block during intergrowth formation, the projected composition Bi4Ba[P]Sr[S]Ti2NbO14Cl (where [P] indicates the perovskite block, while [S] indicates the fluorite block) evolves into the phase with a mixed cation distribution, Bi4Ba0.1[P]Sr0.9[P]Ba0.9[S]Sr0.1[S]Ti2NbO14Cl. The cation migration appears to improve the packing by simultaneously reducing the height of the perovskite block and decreasing the divergence in the Bi-O bond lengths of the fluorite block simultaneously. This leads to greater mixing of Ti-3d, Nb-4d, and Bi6p states contributing near the conduction band minima. The cation-migrated S-A hybrid shows enhanced photocatalytic hydrogen evolution (PHE) as compared to the hybrid perovskites with nonmigrated or unmixed cation distribution. The present investigation discusses the innovative synthesis, cation migration, site disorder, and first-principles electronic structure calculations to unveil their role in enhanced PHE.

The global energy crisis caused by rapid industrialization, population explosion, and enormous emission of greenhouse gases by traditional fuels compels the research community to look for alternate energy sources. Solar energy fits well in the desired criteria as it is free, inexhaustible, substantial, and sustainable. Photocatalysis is touted to be one of the viable routes to efficiently utilize this copious solar power. Hydrogen production by water splitting over semiconductor photocatalysts is one of the lucrative avenues to boost the hydrogen economy. Perovskites and their counterparts have attracted significant attention for photocatalytic hydrogen generation owing to their highly tunable structural, optical, and physicochemical properties. In this chapter, we will discuss layered perovskites (such as Aurivillius, Ruddlesden-Popper, Dion-Jacobson, and Sillén-Aurivillius phases), their advantages, key parameters, and fundamental aspects of photocatalytic water splitting in detail, and their application to devise robust and sustainable photocatalysts. It includes the structural details of the perovskite structures and current challenges in semiconductor photocatalysis and sheds light on the advantages and impediments of different approaches. Furthermore, several examples will be discussed where these approaches are applied to improve photocatalytic performance, along with a focus on promising strategies for practical applications. This chapter aims to provide an in-depth understanding of the development of photocatalysts and their underlying photocatalytic mechanisms. This comprehensive overview is anticipated to inspire new concepts and advancements to accelerate research in the field and circumvent the current energy and environmental problems.

The global water resource shortage has evolved into a pressing concern, necessitating the advancement of effective and environmentally sustainable water treatment techniques. Photocatalysis has surfaced as a hopeful technology for eliminating organic contaminants from wastewater because of its efficiency, cost-effectiveness, and eco-friendliness. Here, CeO2 microspheres and Ni0.5Zn0.5Fe2O4 (NiZn-ferrite) nanoparticles were synthesized using the hydrothermal method, followed by the fabrication of ternary hybrid composites CeO2/NiZn ferrite/multiwalled carbon nanotubes (MWCNT) via ultrasonic treatment. Various analytical techniques including XRD, FESEM, VSM, PL, BET and UV-Visible spectroscopy were employed to characterize the resulting synthesized samples. The hybrid ternary composites demonstrate remarkable efficiency in degradation of reactive red-35 dye through photocatalysis attributed to enhanced surface area. This efficiency is further enhanced when coupled with ultrasonic treatment, leading to a synergistic effect. The catalysts can be easily separated from the suspension due to their magnetic behaviour and thus hold great potential for utilizations in the field of wastewater treatment and environmental remediation.

A sustainable water-resistant binder was developed utilizing flue gas desulphurized (FGD) gypsum and fly ash (FA), which are byproducts of coal-based thermal power plants. FGD gypsum was subjected to calcination, resulting in the formation of beta-hemihydrate plaster. Various trial mixes of binders were then formulated, incorporating different proportions of beta-hemihydrate (50-75%) and fly ash (15-40%), along with a fixed amount of OPC (10%) and activators. The physio-chemical and mechanical properties of the sustainable binders were evaluated, leading to the recommendation of a binder mix (P4) containing 30% fly ash and 60% beta-hemihydrate plaster due to its favorable cost-effectiveness. Binder mixes P4 exhibited a compressive strength of 10.25 MPa after 28 days, with a water absorption rate of 9.25%. To assess the durability of the binders, they were subjected to extreme weather conditions, evaluating their strength under hot and cold temperatures. The binder mixes displayed low thermal conductivities (0.140-0.153 W/m.K), making them suitable for insulation applications. Furthermore, the binders achieved a Class 1 classification based on fire test analysis according to BS 476-1997. The development of these binders serves the dual purpose of waste management by utilizing byproducts and providing an economical alternative to the cement industry for both internal and external applications. It propels the construction industry toward a future characterized by reduced carbon emissions.

The exceptional hike in industrialization has led to water pollution mainly due to the organic wastes from textile, printing and leather industries. Photocatalysis has emerged as one of the best methods to decompose organic waste from wastewater. In this regard, Mg and Co co-doped, Mg0.5Co0.5FeO3 nanoparticles have been synthesized using a modified hydrothermal method followed by annealing at different temperatures (300, 400, 500 and 600°C). The structural properties were investigated with the help of XRD and FTIR. FE-SEM depicted that the synthesized particles have a spherical morphology and the average particle size lies in the nano region (8-20 nm). The photocatalytic activity of the synthesized catalysts was tested under visible light for the degradation of 20 ppm reactive red 35 (RR-35) dye. Thethe enhanced photocatalytic efficiency of F400 can be attributed to its optimum band positions which was confirmed using scavenger tests for the presence of various active species. Further, a combination of sonocatalysis, H2O2, and photocatalysis was employed and this synergistic approach resulted in an impressive enhancement in the degradation efficiency of F400 catalyst.

Water scarcity and contamination are the foremost global one health challenges, which require immediate nano/ biotechnology-based innovative interventions. Hybrid nanocomposites have emerged as novel nanoplatforms for wastewater remediation through photocatalytic degradation of persistent organic pollutants. This unprecedented study reports the economical fabrication of novel nanoplatforms based on Ni0.5Zn0.5Fe2O4 and CeO2 (using the modified hydrothermal method) and their binary and ternary hybrid nanocomposites of Ni0.5Zn0.5Fe2O4/CeO2 and Ni0.5Zn0.5Fe2O4/CeO2/multi-walled carbon nanotubes (MWCNT) (using facile ultra-sonication method) respectively, for water health management. The engineered nanocomposites were evaluated for the Z-scheme mechanism using morphological (SEM, TEM), structural (XRD), optical (UV-Visible spectroscopy), magnetic (VSM), electronic and compositional (XPS) analyses and employed for wastewater remediation. The ternary hybrid composites exhibit excellent photocatalytic degradation efficacy (93.5%) for removing rose bengal (RB) dye from wastewater on UV illumination. The high dye-removal efficacy of ternary hybrid is attributed to the suitable band gap positions of Ni0.5Zn0.5Fe2O4 and CeO2 metal oxides enhancing its photodegradation efficiency on UV illumination, and to the MWCNT enhancing the recombination time of photogenerated electron-hole pairs during dye-removal phenomena. Owing to their excellent performance and robust stability, the engineered ternary composites possess enormous potential for degrading diversified organic pollutants for wastewater treatment and contribute to One Health management, where photocatalytic degradation attributes are a prerequisite.

ABSTRACT This study reported solidification/stabilisation of lead and copper-laden fly ash (adsorbent) utilising cement as binder for their ultimate disposal. The Pb (II) and Cu (II) loaded fly ash was successfully immobilised within the cement matrix without presence of any chemical agents. A retardation of 80–100 min in the setting time of cement paste was noticed on the addition of metal-laden fly ash attributed to the presence of metal ions. However, a gradual decrease in mechanical strength of the mortars was observed with higher amounts of Pb (II) and Cu (II)-loaded fly ash in the mix composition. This decrease is ascribed to the breakdown of calcium silicate hydrate (CSH) gel network in the presence of metal crystallites, as confirmed by scanning electron microscopy (SEM) and energy-dispersive x-ray (EDX) analyses. TG-DTG studies also reveal a decrease in CSH (%) from 4.77% (for fly ash cement mortar) to 4.14% and 3.86% for Pb (II) and Cu (II)-loaded fly ash mortars, respectively. X-ray diffraction (XRD) analysis of metal-laden fly ash cement mortars substantiate the immobilisation of Pb (II) and Cu (II) metal ions in the cement matrix as peaks for Ca[Pb(OH)3]2 and Ca[CuH2O5Si] are visible in their patterns, respectively. TCLP tests conducted on 56 day cured metal-laden fly ash mortars show leachate concentration not exceeding the discharge standards. Overall, these results indicate that this integrated adsorption- solidification/stabilisation process is efficient for safe disposal and utilisation of heavy metal-laden fly ash for building and construction related work as a secondary material. GRAPHICAL ABSTRACT

Flue Gas Desulphurized Gypsum (FGDG) is a by-product generated by the thermal power industry to remove sulfur dioxide (SO2) from flue gas emissions. This paper provides a comprehensive review of flue gas desulphurized (FGD) gypsum production, property, and applications in the construction industry. In 2020, global FGD gypsum production reached an estimated 255 million tons, primarily in Asia (55%), followed by Europe (22%), North America (18%), and the rest of the world (5%). The paper discusses the chemical and physical properties of FGD gypsum, including its composition, crystal structure, particle size, and moisture content. It also reviews the various applications of FGD gypsum, such as in cement and concrete production, agriculture, and gypsum board manufacturing. In the construction industry, FGD gypsum is widely used as a raw material for producing gypsum products, such as plasterboard and cement, due to its high purity and low cost. Moreover, FGD gypsum is increasingly used in agriculture as a soil amendment, which can improve soil structure, increase water retention, and provide essential nutrients to plants. The potential for FGD gypsum to be reused and recycled is also discussed, as well as its environmental impact. FGD gypsum can be safely disposed of in landfills or used for backfilling, with appropriate measures to prevent the leaching of heavy metals and other contaminants. It also delves into the potential benefits of FGD gypsum for improving fire resistance, and acoustic properties, and reducing material waste. With its high purity level and lower cost compared to natural gypsum, FGD gypsum is a viable alternative that can transform the construction industry. This paper also discusses its major drawbacks, such as high SO3 content, dissolution in water, and ettringite formation. This review suggests that there is potential to improve the properties of FGD gypsum further and increase its use as a sustainable construction material in the future.

Development of lightweight plasters for mortar rendering utilizing Flue gas desulfurization (FGD) gypsum have been reported here. Lightweight plasters prepared using FGD gypsum and exfoliated vermiculite were characterized and studied in detail for interior wall applications. Different gypsum vermiculite plasters (GVP) with variable amounts of vermiculite were characterized by X-ray diffraction, scanning electron microscopy and thermal gravimetric analysis. The physicochemical and mechanical properties of all the samples are determined and considered to be efficient for interior applications. An optimum mix composition was selected based on its compressive strength, water absorption and porosity. Water absorption and porosity studies restrict the usage of GVP only to interior wall purposes. The acoustic performance of the materials revealed good sound absorption (α = 0.65). Plasters exhibit satisfactory durability under severe conditions of winter and summer weather. GVP shows excellent fire resistance under BS 476-1997 fire resistance classification with thermal conductivities (< 0.161 W/mK) much lower than standard building materials, which makes them fit for energy efficient insulation materials. These studies depict the efficient utilization of thermal power plant waste, FGD gypsum plaster in interior wall insulation for mortar rendering and can be further extended to exterior construction applications by reducing water absorption.

The photocatalytic activity for wastewater treatment is mainly restricted due to insufficient solar absorption and intense exciton recombination. This article demonstrates an in situ synergistic combination of a photocatalyst and a dye as a type II heterojunction for the collective degradation of water-soluble dyes, pharmaceuticals, and phenolic pollutants. This combination helps to increase visible-light absorption and decrease charge carrier recombination. For this, a series of visible-light-active two-layer Aurivillius perovskites, Bi2.5A0.5Nb1.75Fe0.25O9 (A = Ca, Sr, Ba), was synthesized via the solid-state reaction method. The presence of Fe-doping-induced energy levels is responsible for enhanced visible-light absorption. The semiconductors can efficiently photodegrade bisphenol (BPA), carbamazepine (CBZ), tetracycline (TC), and 4-chlorophenol (4-CP) individually as well as from a mixture by the semiconductors in the presence of RhB. The photocatalytic degradation is driven by a synergistic effect of RhB adsorbed on the surface of the photocatalyst. The RhB-adsorbed semiconductor acts as a type-II heterojunction, which not only enhances light absorption by the photosensitization effect but also improves charge separation and reactive oxygen species (ROS) generation. The strategy will be useful as a sustainable alternative for the degradation of multiple pollutants in wastewater by a unique and straightforward photoexcitation and sensitization process.

A high capacitance of 1039 F g −1 for Co 3 O 4 as compared to 527 F g −1 for CoFe 2 O 4 along with a capacity retention of 86% for up to GCD 5000 cycles, confirm it's potential to be used as an electrode for practical energy storage devices.

Triple-layer Aurivillius perovskites degrade tetracycline antibiotic and rhodamine B together in acidic aqueous solution. Primarily the superoxide radical generated via a semiconductor assisted dye sensitization process degrades the tetracycline.

We report a metal-organic framework (MOF) supported monoligated phosphine-cobalt complex, which is an active heterogeneous catalyst for aromatic C-H borylation and alkene hydroboration. The mono(phosphine)-Co catalyst (MOF-P-Co) was prepared by metalation of a porous triarylphosphine-functionalized MOF (MOF-P) with CoCl2 followed by activation with NaEt3BH. The MOF catalyst has a broad substrate scope with excellent functional group tolerance to afford arene- and alkyl-boronate esters in excellent yields and selectivity. MOF-P-Co gave a turnover number (TON) of 30,000 and could be recycled and reused at least 13 times in arene C-H borylation. Importantly, the attempt to prepare the homogeneous control (Ph3P-Co) using triphenylphosphine was unsuccessful due to the facile disproportionation reactions or intermolecular ligand exchanges in the solution. In contrast, the site isolation of the active mono(phosphine)-Co species within the MOF affords the robust and coordinatively unsaturated metal complexes, allowing to explore their catalytic properties and the reaction mechanism.

Photocatalytic degradation of phenolic dyes has always been a challenge in front of the research community. Therefore, to resolve the problem, present work aims to synthesize the unique cerium oxide nanorods using modified solvothermal method. These nanorods are combined in such a manner that they form spindle-shaped morphology. X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements confirmed the formation of spindle-shaped cerium oxide nanorods. Raman and X-ray photoelectron spectroscopy (XPS) are employed to explore the electronic properties, and lattice defects. The unique morphology and lattice defects are responsible for effective p-Nitrophenol (PNP) degradation up to 90.2 % in 5 h using 6 % Mg doped CeO2 photocatalyst in the presence of UV light. The oxygen vacancies in the form of lattice defects increased the magnetization in Mg doped CeO2 that have been explained based on F-center exchange (FCE) mechanism. Hence, Mg doped cerium oxide has been proven as a bi-functional material for spintronics and photocatalysis.