The search for renewable and clean energy sources is a key aspect for sustainable development as energy consumption has continuously increased over the years concomitantly with environmental concerns caused by the use of fossil fuels. Semiconductor materials have great potential for acting as photocatalysts for solar fuel production, a potential energy source able to solve both energy and environmental concerns. Among the studied semiconductor materials, those based on niobium pentacation are still shallowly explored, although the number of publications and patents on Nb(V)-based photocatalysts has increased in the last years. A large variety of Nb(V)-based materials exhibit suitable electronic/morphological properties for light-driving reactions. Not only the extensive group of Nb₂O₅ polymorphs is explored, but also many types of layered niobates, mixed oxides, and Nb(V)-doped semiconductors. Therefore, the aim of this manuscript is to provide a review of the latest developments of niobium based photocatalysts for energy conversion into fuels, more specifically, CO₂ reduction to hydrocarbons or H₂ evolution from water. Additionally, the main strategies for improving the photocatalytic performance of niobium-based materials are discussed.

Cu‐based catalysts have emerged as critical components in photo‐ and electrocatalysis, offering sustainable solutions for renewable energy and environmental applications. The variable oxidation states of Cu enable diverse catalytic pathways, and its abundance, low cost, and tunable properties have positioned them at the forefront of catalytic innovation. This review provides a comprehensive overview of Cu‐based catalysts applied for sustainable energy production and environmental remediation. The classification of copper‐based catalysts, including metallic copper, copper oxides, copper sulfides, copper halide perovskites, copper‐based metal‐organic frameworks (MOFs), and covalent organic frameworks (COFs), is discussed, highlighting their structural and functional diversity. Various synthesis methods, such as wet chemical approaches, electrochemical and photochemical routes, sputtering, and thermal decomposition, are presented. The applications of copper‐based catalysts in key sustainable energy and environmental remediation processes are explored, focusing on photo‐ and electrocatalysis. Specifically, CO ₂ reduction, water splitting, oxygen reduction, nitrogen fixation, pollutant degradation, and organic synthesis are examined. The mechanisms underlying these processes are analyzed, including the factors influencing their efficiency and selectivity. These applications demonstrate their potential for tackling dual global challenges: diversifying the energy matrix and mitigating environmental issues. By bridging fundamental insights, this review underscores Cu‐based catalysts as a cornerstone in advancing sustainable energy technologies.