TEMPO-oxidized cellulose nanofibers: a renewable nanomaterial for environmental and energy applications

TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidized cellulose nanofibers (TOCNFs), which are derived from abundantly available wood biomass, possess uniform and ultrafine diameters of 3–10 nm and high aspect ratios, and are functionalized with carboxyl groups. The fabrication process of TOCNFs is more environmentally friendly than that of other types of cellulose, such as microfibrillated cellulose (MFC) and cellulose nanocrystals (CNCs), and TOCNFs possess a more uniform and ultrafine diameter. In recent years, TOCNF-based adsorbents, nanocomposites, and membranes have been studied extensively in various fields, such as environmental remediation, energy, and smart materials. This review summarizes the recent advances in the applications of TOCNFs in the abovementioned fields. In particular, the preparation, adsorption ability, and removal efficiency of TOCNF-based absorbents, separation performance of various kinds of TOCNF-based membranes, wide applications of TOCNFs in energy storage and conversion, and TOCNF-based smart materials are discussed. The beneficial role of TOCNFs in the abovementioned applications is highlighted, including their low environmental impact, high aspect ratio, high strength, ability to be functionalized, and renewability. It is believed that this timely review will facilitate further research on the innovation and applications of TOCNFs in fields such as environmental remediation, energy, and smart materials.