Cu-based catalysts have emerged as critical components in photo-and electrocatalysis, offering sustainable solutions for renewable energy andenvironmental applications. The variable oxidation states of Cu enable diversecatalytic pathways, and its abundance, low cost, and tunable properties havepositioned them at the forefront of catalytic innovation. This review provides acomprehensive overview of Cu-based catalysts applied for sustainable energyproduction and environmental remediation. The classification of copper-basedcatalysts, including metallic copper, copper oxides, copper sulfides, copperhalide perovskites, copper-based metal-organic frameworks (MOFs), andcovalent organic frameworks (COFs), is discussed, highlighting their structuraland functional diversity. Various synthesis methods, such as wet chemicalapproaches, electrochemical and photochemical routes, sputtering, andthermal decomposition, are presented. The applications of copper-based cat-alysts in key sustainable energy and environmental remediation processes areexplored, focusing on photo- and electrocatalysis. Specifically, CO2 reduction,water splitting, oxygen reduction, nitrogen fixation, pollutant degradation, andorganic synthesis are examined. The mechanisms underlying these processesare analyzed, including the factors influencing their efficiency and selectivity.These applications demonstrate their potential for tackling dual globalchallenges: diversifying the energy matrix and mitigating environmentalissues. By bridging fundamental insights, this review underscores Cu-basedcatalysts as a cornerstone in advancing sustainable energy technologies.