The temptation from homogeneous linear catechyl lignin

Lignin, one of the largest sources of naturally produced aromatic biopolymer on the planet, is considered as a starting point to generate sustainable chemicals and materials. In 2012, a novel catechyl lignin (C-lignin) bearing caffeyl alcohol subunits and benzodioxane linkages, was discovered in vanilla and cactaceae seed coats. The homogeneity and linearity of C-lignin render it an ‘ideal lignin' archetype for valorization. Over the past decade, experimental and theoretical advances have been made in C-lignin research on the basis of the temptation of this unique biopolymer. This review is devoted to offering recent advances in C-lignin research, covering biosynthesis, separation and characterization, and valorization. Several next steps to further advance the growing of C-lignin are also prospected and proposed.