A review on the emerging applications of cellulose, cellulose derivatives and nanocellulose in carbon capture.

Carbon capture can be implemented at a large scale only if the CO2 selective materials are abundantly available at low cost. Since the sustainable requirement also elevated, the low-cost and biodegradable cellulosic materials are developed into CO2 selective adsorbent and membranes recently. The applications of cellulose, cellulosic derivatives and nanocellulose as CO2 selective adsorbents and membranes are reviewed here. The fabrication and modification strategies are discussed besides comparing their CO2 separation performance. Cellulose nanofibrils (CNFs) and cellulose nanocrystals (CNCs) isolated from cellulose possess a big surface area for mechanical enhancement and a great number of hydroxyl groups for modification. Nanocellulose aerogels with the large surface area were chemically modified to improve their selectivity towards CO2. Even with the reduction of surface area, amino-functionalized nanocellulose aerogels exhibited the satisfactory chemisorption of CO2 with a capacity of more than 2 mmol/g was recorded. Inorganic fillers such as silica, zeolite and MOFs were further incorporated into nanocellulose aerogels to enhance the physisorption of CO2 by increasing the surface area. Although CO2 adsorbents developed from cellulose and cellulose derivatives were less reported, their applications as the building blocks of CO2 separation membranes had been long studied. Cellulose acetate membranes were commercialized for CO2 separation, but their separation performance could be further improved with silane or inorganic filler. CNCs and CNFs enhanced the CO2 selectivity and permeance through polyvinyl alcohol coating on membranes, but only CNF membranes incorporated with MOFs were explored so far. Although some of these membranes surpassed the upper-bound of Robeson plot, their stability should be further investigated.