Abstract
The rapid increase in anthropogenic carbon dioxide (CO2) emissions and the growing global energy demand have intensified the search for sustainable carbon mitigation and clean energy solutions. Nanomaterials have emerged as promising candidates for carbon capture, energy conversion, and storage technologies due to their high surface area, tunable physicochemical properties, and superior catalytic performance. However, conventional nanomaterial synthesis routes often involve toxic chemicals, harsh reaction conditions, and high energy consumption, limiting their environmental sustainability. In this context, green synthesis of nanomaterials has gained significant attention as an eco-friendly alternative that aligns with the principles of green chemistry. This review presents a comprehensive and critical overview of green synthesis strategies for nanomaterials and their applications in carbon capture and clean energy technologies. Biological, green chemical, and low-energy physical synthesis routes are discussed, along with classification of green-synthesized nanomaterials including metal, metal oxide, carbon-based, and biopolymer-based nanocomposites. The role of these materials in CO2 adsorption, carbon capture and storage (CCS), CO2 conversion, solar energy conversion, energy storage, and hydrogen energy systems is systematically analyzed. Environmental impact, toxicity concerns, life-cycle sustainability, and scalability challenges are critically evaluated. Finally, future research directions and technological opportunities are highlighted, emphasizing the potential of green nanotechnology in achieving carbon neutrality and sustainable energy transitions.