Cobalt phosphate (CoPi)-based materials have garnered significant attention recently due to their cost-effectiveness, amorphous structure, and efficient charge separation, which enhance degradation and photocatalytic water splitting. The redox-active nature of cobalt enhances fast electron transfer. Due to their unique arrangement, phosphate groups promote water adsorption and accelerate the dissociation process on the electrode active sites. This work aims to provide an overview of recent advances in CoPi, including computational studies and coordination engineering. Additionally, different synthesis processes of CoPi-based photocatalysts are explored. Focusing on the mechanistic impact of CoPi, this work explores different modification strategies to optimize charge transfer and suppress carrier recombination. The review also highlights CoPi as a functional layer in solar-driven applications for pollutant degradation, H2 production, and oxygen evolution. This study identifies novel strategies for increasing effectiveness, outlines upcoming opportunities and challenges, and concludes by highlighting the significance of these advancements for future applications.

Metal organic frameworks (MOFs) and covalent organic frameworks (COFs) have gained significant attention as promising photocatalytic materials, largely due to their structurally versatile architectures, extensive surface areas, and highly customizable pore characteristics. In addition to the different factors that have been attributed to their high photocatalytic efficiency, it-it interactions are also an important factor that has been less studied. These non-covalent interactions, arising from aromatic it-electron systems, significantly influence the optoelectronic properties. In contrast to previous reviews in which it-conjugation, it-stacking, and photocarrier transfer are treated as distinct or only superficially addressed contributions, this review critically discusses it-it interaction as an integral design principle that regulates the optoelectronic properties and photocatalytic activity of MOFs and COFs. The present review draws on a systematic examination of literature sourced from major scientific databases, with a primary focus on mechanistic studies investigating the role of it-mediated interactions in MOFand COF-based photocatalysts. We first discussed the origin of it-it interactions in MOFs and COFs, highlighting the stacking and delocalized it-conjugation. it-it interactions in MOFs are originally related to the aromatic organic linkers and their special arrangements. Whereas, in-plane it-conjugation and it-it stacking in COFs are related to enhanced charge transport and less recombination. The review further examines the effect of it-it interactions on optoelectronic properties, stability, and adsorption properties of MOFs and COFs. Moreover, this review identifies key design strategies such as it-it stacking, extended it-conjugation, donor-acceptor architectures, and surface functionalization, and discusses their mechanistic contributions, benefits, limitations, and significance in the rational development of high-performance photocatalysts. Furthermore, the important factors for engineering the it-it interactions in MOFs and COFs are also explored. Finally, the applications of it-it interactions modulated MOFs and COFs for H2 production, CO2 reduction and pollutant degradation are also discussed. Finally, the future directions in the field of it-it interactions-based MOFs and COFs photocatalytic systems are discussed. Overall, this review explores the it-it interactions as a parameter to design the efficient MOFs and COFs photocatalytic material for energy and environmental applications.

Manganese dioxide (MnO₂)-based catalysts have emerged as promising candidates for the complete oxidation of volatile organic compounds (VOCs). However, insufficient oxygen mobility and the limited availability of reactive oxygen species restrict their low-temperature catalytic performance. Herein, Ni-doped ε-MnO₂ nanosheet catalysts were synthesized via a redox-precipitation route under two distinct synthesis redox environments by tuning the KMnO₄/Mn2+ ratio. The redox-controlled synthesis generates distinct surface chemistries, leading to different catalytic behaviors toward aromatic and oxygenated VOCs. Comprehensive structural, spectroscopic, and redox characterizations reveal that the catalyst synthesized under Mn2+-rich conditions possesses oxygen-vacancy-rich surfaces together with enhanced oxygen mobility and MnONi redox interactions, which correlate with superior low-temperature oxidation of toluene. In contrast, the catalyst prepared under KMnO₄-rich conditions exhibits more pronounced carbonate-modified surface chemistry, which is associated with enhanced ethyl acetate oxidation. The optimized catalysts achieve T₉₀ values of 238 °C for toluene and 198 °C for ethyl acetate oxidation. Catalytic tests under an inert atmosphere further support the direct participation of catalyst oxygen species, consistent with a Mars-van Krevelen-type oxidation mechanism. Moreover, the catalyst synthesized under Mn2+-rich conditions maintains nearly complete ethyl acetate conversion for 48 h at 220 °C. These results demonstrate that controlling the synthesis redox environment provides an effective strategy to tailor surface chemistry and oxygen activation in Mn-based catalysts, offering new insights into the rational design of efficient catalysts for VOC oxidation.

Organic–inorganic S-scheme heterojunctions (OI-SHJ) have been developed as an emerging photocatalytic platform for the solar-driven H2 production. In this review, comprehensive discussion is presented on the design and mechanistic understanding of OI-SHJ photocatalysts with a focus on the engineering of the heterointerface, modulation of the band alignment and the role of the internal electric field to direct charge transfer pathways. Strategies involving S-scheme structures with polymers, covalent organic frameworks, carbonaceous materials and metal–organic frameworks are explored, with a particular attention placed on the impact of molecular tuning, defect engineering and interfacial coupling on photocatalytic H₂ production. In addition, the systematic correlation of the synthesis approaches, electronic structure control and the charge transfer pathway along with the influence of structural design on photocatalytic performance, durability and carrier migration is critically discussed. Lastly, the current issues of scalable synthesis, interfacial stability and electronic modulation of solar-to-hydrogen conversion are highlighted for future perspectives of sustainable solar-to-H2 conversion.

Harnessing solar energy through photocatalysis offers a promising pathway for sustainable energy conversion and environmental remediation. Central to this progress is the development of efficient photocatalysts capable of activating inert N2 molecules under mild conditions. Recently, dual-atom catalysts (DACs) have emerged as a transformative class of materials that bridge the gap between single-atom and nanoparticle catalysts by providing synergistic bimetallic active sites with maximized atomic utilization. This review concisely summarizes recent advances in the coordination microenvironment, structural design, and catalytic mechanisms of transition metal-based dual-atom catalysts (TM-DACs) for photocatalytic N2 conversion. Particular emphasis is placed on how electronic coupling, metal–metal interactions, and coordination configuration of TM-DACs govern charge transfer dynamics, adsorption behavior, and reaction kinetics during the N2 reduction process. Synthesis strategies, characterization techniques, and mechanistic pathways of TM-DACs are comprehensively discussed, highlighting their advantages over single-atom systems. Furthermore, emerging trends and challenges in developing noble metal-free, earth-abundant DACs for efficient NH3 production are outlined. This review aims to provide fundamental insights and design principles for constructing next-generation TM-DACs for highly efficient and sustainable photocatalytic applications. Schematic of the coordination microenvironment and dual-metal synergy in transition metal-based dual-atom catalysts (TM-DACs) for photocatalytic N2 fixation. Design strategies, active site interactions, charge transfer pathways, and reaction mechanisms are highlighted to guide the development of effective and sustainable photocatalysts for NH3 production.

With remarkable physical and chemical characteristics like high surface area, tunable porosity, and modified surface functions, architecturally engineered carbon materials have become adaptable catalytic material for various advanced oxidation processes. Herein, the state-of-the-art in the catalytic ozonation of organic pollutants using structurally as well as functionally engineered carbon architectures are thoroughly reviewed. We have discussed the structural and electronic properties of architecturally engineered carbon including aerogels, foams, and frameworks that underpin their catalytic efficiency. The role of these materials in O3-based degradation route is provided, highlighting their synergistic interactions with O3 and the generation of active species. Different fabrication routes for these advanced carbon catalytic materials are reviewed, that enable control over structure and functionality. Kinetic aspects of O3-based catalytic degradation are presented, highlighting how different factors govern the pollutant degradation efficacy. An in-depth analysis is also given to provide the significant role of both radical and non-radical ways in the breakdown of toxic pollutants. Lastly, future perspectives are outlined, emphasizing the need for deeper mechanistic understanding and the design of multifunctional catalytic material with improved stability as well as reusability. This review aims to offer a comprehensive foundation for the progress of next-generation architecturally engineered carbon in catalytic ozonation, guiding future innovations toward sustainable water treatment solutions.

The TiO2/ZnIn2S4 heterojunction photocatalysts are shown to be a promising range of materials to overcome the critical challenges in field of sustainable energy conversion and pollution remediation. The structural stability of TiO2 and ZnIn2S4 synergistically overcomes the intrinsic shortcomings of the respective materials, including poor solar absorption and high charge recombination rate. It has recently been shown that a rational design based on morphology, electronic structure, and interfacial properties is essential for further enhancing photocatalytic activity. The analysis summarizes the recent advances toward the strategies and optimization of TiO2/ZnIn2S4 heterostructures in terms of controlled synthesis, modulation of morphology, heteroatom doping, and defect engineering. Advanced architectures (1D/2D, 2D/2D and hierarchical) are highlighted to optimize the light harvesting, exposure of reactive sites and charge transfer. Doping and vacancy engineering to achieve an optimized band structure, create internal electric fields, and reduce recombination are carefully examined. In conjunction with this, the development of the typical heterojunctions of Type II and Z-scheme and S-scheme is discussed and the effect of the development in charge separation and redox properties is explained. Their multifunctional uses, including photocatalytic production of H2, reduction of CO2 and degradation of pollutants are well summarized with detailed mechanistic insight. Finally, the most important challenges for defect control, stability and scalability are discussed and areas for future work are suggested.

Defect engineering has been recognized as a powerful strategy for tailoring the electronic structure of nanomaterials, representing a paradigm shift in nanoscience from passive defect tolerance to deliberate defect design. This study aims to elucidate how oxygen vacancies (OVs) influence the photocatalytic performance and structural properties of Bi4Ti3O12 (BTO). Advanced characterization techniques were employed to investigate formation of OVs, electronic structure, charge density distribution, charge migration and separation and molecular activation in BTO. Strategies for introducing OVs, such as dopant incorporation, chemical reduction, and thermal treatments, were systematically reviewed. The effects on band-gap modulation and charge-carrier dynamics were further examined, with particular emphasis on BTOOV-based heterojunctions and metal-deposited systems. Oxygen vacancies effectively narrow the band gap and enhance charge separation, thereby improving photocatalytic activity. BTOOVs systems demonstrate strong potential in environmental and energy applications, including pollutant degradation, CO2 reduction, and H2 evolution. This review highlights the critical role of precise defect control in optimizing photocatalytic efficiency and guides the rational design of sustainable, light-driven catalytic systems.

S-scheme heterojunctions have developed into a highly effective methodology for photocatalysis, due to their ability to improve charge dissociation while sustaining a substantial redox potential. Among semiconductors that can be activated with visible light, copper bismuthate (CuBi2O4) is particularly appealing due to its narrow band gap, visible light absorption, and suitable band alignment. Yet, its photocatalytic activity is limited by low charge mobility and fast recombination of photoinduced carriers, which justifies its integration into S-scheme heterojunctions. For this, the review aims to explore the photoactive CuBi2O4, S-scheme heterojunctions, focusing on their structural and electronic properties while unravelling their charge transfer processes for the first time, and advanced mechanisms of charged S-scheme operation. Notably, these include the use of density functional theory to predict electronic band alignment and charge carrier dynamics for advanced in-situ XPS, electromagnetic resonance to track reactive radical species and to electrochemical analysis for separation, redox equilibrium and photocatalytic efficiency, and charge evaluation. This collection of characterization attempts an understanding of the mechanistic photocatalytic pathway. This review also discusses the shift in designs from conventional to dual and triple S-scheme architectures, recent efforts on photocatalytic degradation of wastewater pollutants (dyes, antibiotics, and others) and addresses numerous other important aspects such as mechanistic depth, stability, scalability, and photocatalytic activity. Finally, new pathways are suggested that aim to strengthen CuBi2O4-based S-scheme photocatalysts for photocatalytic environmental remediation.

Noble-metal plasmonic photothermal catalysis has become a viable method to enhance catalytic behaviour owing to the synergistic nature of photonic and localized thermal excitation. In the present review of the status of the noble plasmonic metal photothermal catalytic systems, the developments are summarized in detail with a specific focus on the structural design and mechanistic understanding. Initially, the theory of plasmonic photothermal catalysis, including localized surface plasmon resonance (LSPR), hot carrier generation and transfer, and near-field electromagnetic enhancement, which are all combinations of light harvesting and catalytic behaviours, is also addressed. The optical behaviour dependence on morphology-dependent parameters, such as particle size, shape, and structural symmetry, and catalytic efficiency is critically analyzed. In addition, the importance of the creation of heterojunctions between noble metals and semiconductor materials is also explained for the promotion of charge separation, the intensity of interactions at the interface, and the stability of catalysts. Systematic discussions on these catalytic systems have been utilized in energy conversion and environmental remediation in the form of the production of solar fuels and pollutant degradation. Finally, there are issues that exist concerning mechanistic insight, long-term stability and scalability, which are also articulated and provide insights into the rationalize for future development of better plasmonic photothermal catalyst.

Growing concerns regarding environmental and energy challenges have substantially contributed in the development of efficient and sustainable PWS (photocatalytic water splitting) techniques has been greatly aided by. Beyond enormous photocatalytic materials, CPs (coordination polymers), which are made from metal nodes and organic linkers, have demonstrated extensive potential because of their structural tunability, suitable Eg (energy bandgap) energies, and ability to enable efficient charge separation. High surface areas, dual active sites, a variety of pore architectures and tunable functionalities are some of the distinctive structural features of CPs that cooperatively enhance light harvesting, enable photoinduced charge carrier separation and transport, and promote efficient interaction between catalytic sites and water molecules. These characteristics play a major role in upgrading the overall functioning of PWS systems. In this review, we first examine the detailed molecular structure of CPs using a computational approach. Following this, the classification of CPs is presented, with a particular emphasis on different metal-centered frameworks, dimensionality, and porosity, along with modification strategies. These metals are of particular interest due to favourable redox properties, variable coordination geometries, and strong light absorption capabilities. Moreover, the role of different ligands and heterojunction in CPs have been explored. The construction of heterostructures based on these metals facilitates efficient charge separation, which is critical for effective photocatalytic applications. Additionally, the mechanism of photocatalytic OWS (overall water splitting) has been discussed, with an emphasis on the fundamental processes of light absorption, photocarriers separation, and surface redox reactions involved in H2 and O2 evolution. Besides this, we also provided a brief overview of the role of interfacial defects, active sites, and co-catalysts, as well as the unique advantages of CPs in photocatalysis. In addition, recent applications of CP-based photocatalysts for PWS are highlighted, with particular attention to mechanistic insights and performance. Finally, the review summarised by outlining the key disputes and future research directions for advancing CP-based photocatalysts in OWS applications.

Boron Nitride, a typical 2D wide-bandgap material formerly considered chemically inert, has now been transformed into a versatile photocatalytic material due to the tunable function of surface defects. In this critical review, we evaluate the properties, formation, and function of the surface defects in BN, focusing on the influence of surface defects on the photo-degradation and photocatalysis performance for the solar-to-fuel conversion. The major classes of defects have been classified, including native vacancies, n-dopants, structural perturbations, and topological manifold generations. This lends insight into their impact on charge carrier behavior, electronic structure, and interfacial chemistry based on experiment and first-principle theory. The relationship of these defects with photocatalytic performance is addressed over a broad range of signature reactions such as H2 evolution, CO2 reduction, pollutant degradation, and N2 fixation. Finally, emerging strategies such as atomic-scale defect modulation, machine learning design, and defect-mediated heterojunctions have been explored for the BN-based photocatalysts. The present contribution thus brings together the established knowledge and paves the way for the future of defect-based boron nitride systems for sustainable photochemical applications.

Graphitic carbon nitride derivatives have received wide attention as sustainable, metal-free photoactive catalyst. Among other derivatives, N-rich-g-C3N4 i.e. g-C3N5 has newly emerged as a next-generation catalytic semiconductor with improved electronic and structural characteristics than g-C3N4. The higher N-content as well as exclusive motifs like: triazole, triazine, and heptazine units, give g-C3N5 with a lower bandgap, extended It-conjugation, boosted charge transfer, and stronger absorption of visible-light. Numerous N-rich precursors and synthesis methods allow the formation of frameworks containing triazole linkages, triazine combinations, and azo bridges, providing flexible routes for the modifying its structure. A thorough discussion on fabrication and characterization is highlighted, focussing on their influence on optical and electronic efficacy. Special emphasis is given to Z- and S-scheme heterojunctions, which create internal electric fields and promising band bending, thereby helping directional charge migration while conserving high oxidation and reduction potential. These heterostructures enhance visible-light utilization and catalytic stability in both energy and environmental applications. Furthermore, functionalization, porosity engineering, and defect regulation have extended the reactivity of g-C3N5, representing its versatility in complex catalytic systems. This review highlights the fundamental properties, structural engineering approaches, and emerging applications of g-C3N5, while also addressing the challenges that remain for advancing its role in sustainable photocatalysis.

H2 and O2 generation are vital in pursuing sustainable energy, aligning with Sustainable Development Goal 7. 2D photocatalysts are promising due to their unique structure and high surface-to-volume ratio, enhancing catalytic efficiency. Carbon-based materials stand out for their excellent it-it conjugation, strong light absorption, and chemical versatility. Despite limitations, they hinder their broad-scale use, such as limited charge carrier kinetics, restricted light absorption, suboptimal quantum efficiency, graphene's chemical inertness, and agglomeration issues. This review paper mainly highlights the role of metal-free defects in 2D nanocarbons in revolutionizing solar-to-energy conservation. These metal-free photocatalysts are promising candidates for sustainable catalytic processes owing to the defect sites in the carbon matrix, categorized as metal-free point defects and volume defects. The main emphasis is on understanding how point and volume defects improve the overall photocatalytic efficiency. Point defects, including carbon and nitrogen, usually disrupt the electron distribution in the lattice, and volume defects, involving lattice distortions, edge defects, Stone-Wales defects, and pits/voids, generate abundant active sites. This integrated approach, combining defect engineering, material diversity, and practical applications, positions the review as a significant and innovative contribution to the field. Leveraging the properties of carbon-based 2D materials and addressing various challenges through defect engineering can lead to the development of highly effective and sustainable photocatalysts, advancing renewable energy efforts and contributing to global sustainability.

Electrocatalytic glucose oxidation reaction (GOR) has emerged as a potential strategy for energy-saving hydrogen production. The limited electrocatalytic performance of utilized materials has been considered a bottleneck issue. Herein, we present the preparation of Fe-N-C catalyst-encapsulated nickel foam (Fe-N-C/NF) via a one-pot and facile hydrothermal method, employing collagen to provide a coordination environment. Electron microscopy techniques, X-ray photoelectron spectroscopy, positron annihilation spectroscopy, and density functional theory calculations unambiguously confirm the Fe-N-C species encapsulated on the NF support. Impressively, the achieved Fe-N-C/NF electrode, possessing a high number of active sites, high kinetics, and enhanced charge transport capability, displays outstanding electrocatalytic glucose oxidation activity. The low potential values of 1.31, 1.50, and 1.70 V vs. RHE are required to reach the current density of 10, 50, and 100 mA & sdot;cm-2, respectively, which are found to be significantly lower than those of the oxygen evolution reaction (OER) counterpart (e.g., 1.57, 1.75, and 1.91 V vs. RHE), implying the outstanding GOR performance of the Fe-N-C/NF material and its potential in the energy-saving hydrogen production. Moreover, the obtained catalyst exhibits stability and a lower working cell voltage for GOR in comparison to OER counterparts, suggesting an impressive application of the electrode for energy-saving hydrogen production via GOR.

Graphdiyne (GDY) is a new two-dimensional carbon allotrope, recognized as a promising material for photocatalytic CO2 reduction because of its unique sp-sp(2) hybridized network and tunable bandgap and extraordinary charge transport characteristic. The growing requirement for sustainable CO2 conversion processes has fueled tremendous research activities on GDY-based photocatalysts, due to their improved light harvesting potential, charge separation capabilities, and catalytic site availability as compared to traditional materials. Herein, we review the recent progress on GDY-based strategies in CO2 reduction with an argument towards GDY metallation, metal-free GDY, heterostructures including GDY, and theoretical studies. In situ spectroscopic studies along with density functional theory (DFT) calculations provide mechanistic insights into the decisive pathways behind CO2 activation, charge transfer, and product selectivity. This review is a comprehensive discussion extended on the synthetic methodologies and new computational insights that bring forth a rational basis for designing next-generation GDY-based photocatalysts. Integrating experimental advances with theoretical understanding, this work provides a roadmap for bridging the gap between materials design and practical photocatalytic application, providing perspectives on challenges and opportunities for GDY-based CO2 conversion technologies in the future

This review highlights face-to-face 2D/2D S-scheme photocatalysts for CO2 reduction, focusing on charge transfer, interfacial design, and performance and offering insights into improving photocatalytic efficiency through material engineering.

Metal-organic frameworks (MOFs) have emerged as a significant class of heterogeneous photocatalytic materials owing to their structural tunability and high porosity. Among them, two-dimensional MOFs (2D MOFs) have gained increasing attention for various photocatalytic applications due to their ultrathin layered structures, large surface areas, abundant exposed active sites, and enhanced charge migration characteristics. Compared to their 3D counterparts, 2D MOF-derived nanocomposites often exhibit improved photocatalytic efficiency. Recent studies have emphasized the rational design of 2D MOFs through precise control of metal nodes, organic linkers, and structural morphology to tailor their photocatalytic properties for specific targets. This review provides a concise overview of fabrication and postsynthetic modification strategies to enhance the photocatalytic performance of 2D MOF-derived nanocomposites. Practical applications, including environmental remediation, are discussed to demonstrate their real-world potential. Furthermore, the review highlights the intrinsic relationship between 2D MOF structure and photocatalytic behavior, along with current challenges such as structural instability, scalability, and limited visible-light absorption. Finally, key perspectives and future directions are proposed to guide the development of robust, efficient, and sustainable 2D MOF-based photocatalytic materials.

Herein, a Cu/Cu2O-decorated nickel foam (named Cu/Cu2O/NF-Gly) is synthesized and used as a bielectrocatalyst for the hydrogen evolution reaction (HER) and glucose oxidation reaction (GOR). This material is synthesized via a facile glycerol-assisted hydrothermal method, in which glycerol functions as a critical agent, preserving the NF support and driving the growth of Cu and Cu2O phases. Characterization results prove the presence of Cu and Cu2O phases on the NF support. Furthermore, positron annihilation spectroscopy measurements reveal the complete architecture of the material, in which Cu and Cu2O phases are directly bonded to the NF support via Cu-Ni and Ni-O-Cu bonds, respectively. Density functional theory calculations also prove the structural stability and strong capabilities of Cu/Cu2O/NF-Gly for the HER and GOR. Consequently, the prepared Cu/Cu2O/NF-Gly electrode exhibits excellent electrocatalytic activities in both reactions. Impressively, when the prepared catalyst is employed as the cathode and anode, it exhibits a remarkable hydrogen evolution rate of 2.75 mmolh(-1)cm(-2), corresponding to the remarkable Faradaic efficiency of 100.1% for hydrogen in hydrogen production-coupled glucose oxidation applications at 1.7 V vs reversible hydrogen electrode. Our results underscore the potential of using Cu/Cu2O nanoparticle-decorated NFs to produce valuable chemicals in hydrogen production-coupled glucose oxidation systems.