Ammonium persulfate (APS) oxidation was employed to isolate carboxyl cellulose nanocrystals (CNCs) from hybrid poplar residue. Structure changes resulting from APS oxidation were investigated by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). The further oxidation of the ensuring CNCs with sodium periodate manifested selective oxidation of hydroxyl groups at the C6 position of cellulose into carboxyl groups during APS oxidation. The introduction of active carboxyl groups resulted in lower thermal stability. Transmission electron microscopy (TEM) and width distribution showed that the produced CNCs ranged from 10 nm to 24 nm. Carboxyl CNCs with a yield of 63.2% were isolated via APS oxidation, and they were suitable for large-scale CNCs production.

In this study, cellulose nanocrystal (CNC) extracted from hybrid poplar residue was grafted with an aminosilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane (AEAPMDS). Supercritical CO2 drying was employed to produce polymer aerogels. The effects of AEAPMDS on the properties of the aerogel were investigated. Fourier transform infrared spectroscopy confirmed that the aminosilane had been grafted on CNC. The crystallinity decreased due to the introduction of amorphous AEAPMDS on the surface of CNC. Analysis of specific surface areas and pore diameters indicated that the modification failed to destroy the inner structure of the aerogel. Scanning electron microscopy and thermogravimetry revealed that three-dimensional network structure was conserved after modification but had a lower thermal stability. High CO2 adsorption capacities (1.7 and 2.6 mmol g−1) were measured at 1 bar and two temperatures, 25 and 0 °C, respectively. Therefore, the modification procedure could be a promising avenue for the preparation of aminosilane-functionalized CNC aerogels as a novel adsorption material.