Visible-Light Photocatalysis in Green Solvents: Mechanistic Insights, Process Integration, and Sustainable Design Strategies

Hussein Ali Ahmed 1, Shatha Abd Aljabbar 2, * and Ahmed Zamil Hattab 3

1 Department of Chemistry, College of Pure Sciences, University of Karbala, Karbala, Iraq.
2 Department of Biology, College of Education for Pure Science, University of Kerbala, Iraq.
3 Department of Chemical processing engineering, College of chemical engineering, University of Technology-Iraq, PO Box 35010, 52 Alsinaa St., Baghdad, Iraq
* Corresponding Author
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Review
World Journal of Chemical and Pharmaceutical Sciences, 2026, 09(01), 085–098.
Article DOI: 10.53346/wjcps.2026.9.1.0030
Publication history: 
Received on 15 August 2026; revised on 20 September 2026; accepted on 22 September 2026
 
Abstract: 
This would contribute to achieving a paradigm change in visible-light photocatalysis using green solvents that contain photoredox chemistry fundamentals together with the knowledge accumulated from materials science and gentler process Green Chemistry principles directions leading to sustainable chemical syntheses. The present review summarizes the theoretical principles of designing molecular, mechanistic and engineering factors for photocatalytic reactions under environmentally benign (green solvent) conditions in lieu of water; bio-derived solvents such as alcohols/phenols; ionic liquids (IL); and deep eutectic solvents. We emphasize the consideration of solvent polarity, hydrogen-bond networks, viscosity and photophysical transparency on excited-state energetics to rationalize theory/predictions for subsequent electron-transfer pathways progressing in reaction conditions that affect catalyst stability/overall turnover efficiency. Novel design principles limiting synergy for synergistically less reactive (high-volume solvent classes) but net-green ones based on performance and sustainability trade-off comparisons per natural unit or cost. This review then incorporates green-solvent photocatalytic systems into quantitative sustainability metrics (E-factor, PMI and energy efficiency) to further this aim while illustrating their likely usefulness as an industrial process beyond the interests of basic research. The process sustainability puzzle is furnished with a life-cycle assessment carrying all aspects facing the recyclability of solvents. Thereafter, 3 specific technical bottlenecks limiting the total action are examined including limited photon penetration depth to the reaction zone; mass -transport limitations in high microorganism density environments and difficulties related to scale up. They also consider the new potential in areas such as solar-driven photochemistry, use of machine learning for optimization of reaction conditions and modular continuous−flow reactor technologies. Altogether, all of these advances lead to a future where a green−solvent photocatalysis platform for industrial application may enable greener chemical transformations with the advantages of unprecedented selectivities with little waste and inherent energy efficiency. This review broadly compiles the current roadmap of full-integrated and sustainable photocatalytic procedures in ecological solvents, identify existing challenges limiting their practical realisations and propose future perspectives for researchers, process engineers as well as industrial practitioners.
 
Keywords: 
Green solvents, Visible‑light photocatalysis, Sustainable synthesis, Deep eutectic solvents (DES), Solar photochemistry
 
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