Erbium, classified as a lanthanide and rare earth element, demonstrates significant characteristics as green catalysts in its Er(III) salts: affordability, accessibility, support for mild reaction conditions, and multiple reuse cycles without elaborate purification steps or notable activity loss. While Er(III) salts can function both homogeneously and heterogeneously as catalysts, their main applications remain homogeneous, with limited documentation of their heterogeneous catalytic capabilities.