The accelerating depletion of fossil fuel reserves, increasing anthropogenic carbon emissions, and growing industrial demand for sustainable chemical manufacturing have intensified global efforts toward the development of highly efficient catalytic systems and renewable energy technologies. Conventional catalytic materials frequently suffer from poor atom utilization efficiency, limited active-site accessibility, catalyst deactivation, and inadequate long-term stability under harsh operational environments, thereby restricting their applicability in environmentally benign synthesis and advanced energy conversion systems. In this context, functional nanomaterials have emerged as transformative catalytic platforms owing to their tunable electronic structures, exceptionally high surface-to-volume ratios, quantum confinement effects, defect-rich architectures, and synergistic interfacial properties. These unique physicochemical characteristics enable superior catalytic activity, enhanced selectivity, accelerated charge-transfer kinetics, and minimized energy consumption in diverse green synthetic processes and sustainable energy applications. Recent advances in nanostructured catalysts, including heteroatom-doped carbon frameworks, metal-organic frameworks, single-atom catalysts, plasmonic nanostructures, layered transition-metal dichalcogenides, perovskite-derived composites, and hybrid semiconductor interfaces, have significantly improved atom economy and reaction efficiency in photocatalytic, electrocatalytic, and thermocatalytic transformations. Furthermore, the integration of multifunctional nanocatalysts into hydrogen evolution systems, oxygen reduction reactions, carbon dioxide reduction technologies, fuel cells, metal-air batteries, supercapacitors, and next-generation solar energy devices has opened new pathways toward carbon-neutral energy infrastructures (Faazal et al., 2023). Emerging fabrication strategies involving defect engineering, surface functionalization, hierarchical nanoarchitectures, and machine-learning-assisted catalyst design are further accelerating the discovery of highly durable and scalable catalytic materials. This review highlights the novelty of integrating multifunctional nanocatalysts with sustainable energy technologies through atom-efficient reaction engineering and environmentally compatible synthesis pathways. Particular emphasis is placed on the structure–property–performance relationships governing catalytic efficiency and energy-device integration. This article aims to critically analyze recent progress, unresolved scientific challenges, and future opportunities associated with functional nanomaterials for sustainable catalytic chemistry and advanced clean-energy systems.