Sustainability insights into photocatalytic CO2-to-CH4 conversion utilizing g-C3N4-based photocatalysts: Flaws, progress, and prospectives
Silerio-Vázquez F.D.J. Kakavandi B. Tayyab M. Baigenzhenov O. Hosseini-Bandegharaei A. Proal-Nájera J.B.
1 November 2025Elsevier B.V.
Coordination Chemistry Reviews
2025#542
Atmospheric carbon dioxide (CO2) levels increased from 419.3 ppm (ppm) in 2023 to 425.4 ppm in 2024, 51 % above preindustrial levels, with emissions rising from 37.01 to 37.41 billion metric tons. This surge has driven record global temperatures, with annual mean surface temperatures reaching 1.45 °C and 1.55 °C above preindustrial averages in 2023 and 2024, intensifying glacial melt, sea-level rise, and extreme weather events. Photocatalytic CO2 reduction to methane (CH4) has emerged as a promising pathway to mitigate CO2 emissions while producing an energy carrier compatible with existing infrastructure. This review focuses on advancements in photocatalysts based on graphitic carbon nitride (g-C3N4) for photocatalytic CO2-to-CH4 conversion, offering a sustainability-centered perspective often overlooked in previous reviews. In addition to summarizing progress in dopant integration, heterojunction formation, and charge separation strategies, this work critically examines the environmental footprint of precursor materials and the energy consumption of thermal, microwave, and plasma-assisted synthesis methods. It highlights the potential of solar and LED light sources as scalable, energy-efficient alternatives to conventional lamps. The review also addresses practical challenges such as CO2 purification, impurity tolerance in exhaust-fed systems, and the feasibility of CH4 recovery and separation. Furthermore, it explores the integration of photocatalytic CO2 reduction with emerging approaches like direct air capture, electrocatalysis, biophotocatalysis, and computational tools including machine learning and multiphysics modeling. By aligning CH4 production performance with system-level sustainability criteria, this review establishes a framework to guide future developments toward environmentally viable photocatalytic CO2-to-CH4 technologies.
Carbon neutrality , Carbon recycling , CO2 reduction , Greenhouse gas reduction , Photocatalytic efficiency , Solar fuels
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CIIDIR-Durango, Instituto Politécnico Nacional, Calle Sigma 119, Fraccionamiento 20 de Noviembre II, Durango, C. P. 34220, Mexico
Department of Environmental Health Engineering, Alborz University of Medical Sciences, Karaj, Iran
Institute of Materials Research, Tsinghua Shenzhen International Graduate School, Tsinghua University, Guangdong, Shenzhen, 518055, China
Department of Metallurgical Engineering, Satbayev University, Almaty, Kazakhstan
Faculty of Chemistry, Semnan University, Semnan, Iran
Department of Sustainable Engineering, Saveetha School of Engineering, SIMATS, Tamil Nadu, Chennai, 602105, India
Research and Innovation Cell, Rayat Bahra University, Punjab, Mohali, India
CIIDIR-Durango
Department of Environmental Health Engineering
Institute of Materials Research
Department of Metallurgical Engineering
Faculty of Chemistry
Department of Sustainable Engineering
Research and Innovation Cell
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