Biomass and waste exhibit great potential for replacing fossil resources in the production of chemicals. The search for alternative reaction media to replace petroleum-based solvents commonly used in chemical processes is an important objective of significant environmental consequence. Recently, bio-based derivatives have been either used entirely as green solvents or utilized as pivotal ingredients for the production of innovative solvents potentially less toxic and more bio-compatible. This review presents the background and classification of these new media and highlights recent advances in their use in various areas including organic synthesis, catalysis, biotransformation and separation. The greenness, advantages and limitations of these solvents are also discussed.

Glycerol, an organic waste generated by the biodiesel industry, has been recently proposed as a valuable green solvent. This review summarizes the advantages, disadvantages and potential uses of glycerol as a green solvent for catalysis, organic synthesis, separations and materials chemistry. In particular, through selected examples we show here that glycerol may combine the advantages of water (low toxicity, low price, large availability, renewability) and ionic liquids (high boiling point, low vapour pressure, low solubility in scCO₂). More generally, all these reported works contribute to increase the portfolio of available green solvents and afford innovative solutions to the substitution of the conventionally used volatile organic solvents.

Simple and green synthetic procedures constitute an important goal in organic synthesis. The combination of multicomponent reactions (MCRs) and unconventional solvents has become a new research direction, which enables simultaneous growth of both MCRs and green solvents toward ideal organic synthesis. This review summarizes recent results of MCRs obtained in unconventional media including water, ionic liquids, polyethylene glycol and bio-based solvents.

Formic acid is a main product from biomass-derived carbohydrates and is attracting ever more attention as a sustainable hydrogen source, owing to its high volumetric hydrogen density of 53 g of H₂ per liter. In this review, we give an overview of the formic acid mediated transformations of biomass-based feedstocks into added-value products, including biofuels; attention will be primarily focused on the transformation of biomass-derived platform chemicals, with an emphasis on levulinic acid. Formic-acid mediated lignin depolymerization and biomass-oil upgrading will be also discussed.

Dipolar aprotic solvents (DMSO, DMF, DMAc, NMP, etc.) have been widely used in organic synthesis and pharmaceutical research because of their remarkable polarities and solubilities, while most of them are not green because of their detrimental effects on human health and hazards to the natural environment caused by their inescapable toxicity as well as large wastewater streams and high-energy-input requirements. This dangerous situation is further complicated by the surging demand of dipolar aprotic solvents in the research and development in the pharmaceutical industry and other chemical processes. Therefore, minimizing and avoiding the use of such solvents has become one of the most important facets of green chemistry. So far, substantial efforts have been devoted in response to this problem that has entailed the development of green and novel reaction systems that fulfill numerous requirements, which are also met by traditional dipolar aprotic solvents. In this context, this review summarizes the methods and strategies for replacing non-green polar aprotic solvents, which mainly include direct replacement with new green alternatives and utilization of polarized catalysts in common green solvents for avoiding the use of conventional polar aprotic solvents. Besides, the strengths and weaknesses of these two strategies are analyzed. Compared with the direct replacement strategy, the rational design of polarized catalysts not only expands the choice of green solvents, but also provides new possibilities for the design and preparation of multifunctional catalysts, suggesting a promising prospect in substitution strategies for non-green polar aprotic solvents. Certainly, other methods are being explored to realize the green and sustainable replacement of conventional dipolar aprotic solvents in an economical and handy tactic.