CO₂ switchable solvents for sustainable dissolution, modification, and processing of cellulose materials: a critical review

Cellulose is a biopolymer with numerous applications ranging from food packaging to pharmaceutical formulations. However, the sustainability and use of cellulose materials is hindered by harsh processing conditions and toxic solvents. In recent years, a milder approach to cellulose processing and modification has emerged based on the use of CO₂ switchable solvents. They facilitate the dissolution of cellulose through its activation with a base and CO₂. Cellulose can then be regenerated in a range of morphologies (fibres, films, gels), or chemically modified in a controlled homogeneous manner. This not only avoids the need for toxic solvents, but prevents the waste associated with traditional heterogeneous cellulose modification. Based on the literature to date, we provide both a guide to the use of CO₂ switchable solvents for cellulose dissolution and modification, and a critical analysis of these emerging methodologies for future applications of this important biobased material.