New composites consisting of 2% cellulose nanocrystals (NC) of various surface chemistries (i.e., carboxylic acids, sulfonic acids, and amines) incorporated into UiO-66 are synthesized. Nanocellulose and the composites are characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, N2 and CO2 adsorption, and thermogravimetric analysis. The analyses reveal information about the crystallinity, pore structure, and thermal stability of the composites. The results show a marked development of microporosity (≈30%), which is linked mainly to the formation of a NC/UiO-66 interface, to disturbances in the UiO-66 nucleation process, and to missing cluster defects. The latter is related to the geometrical constraints of metal– organic framework (MOF) crystallization around the NC nuclei. Pore size distributions do not depend markedly on the chemistry of NC. While pores in the composites with sizes <0.5 nm are associated with the involvement of NC functional groups in the formation of MOF units, the pores with sizes >1.1 nm have their origin likely in missing linkers and missing clusters. Moreover, the surface chemistry of NC and that of the interface affects the amount of CO2 adsorbed and the strength of adsorption.

Effect of the Incorporation of Functionalized Cellulose Nanocrystals into UiO-66 on Composite Porosity and Surface Heterogeneity Alterations

Alfonso Policicchio;
2020

Abstract

New composites consisting of 2% cellulose nanocrystals (NC) of various surface chemistries (i.e., carboxylic acids, sulfonic acids, and amines) incorporated into UiO-66 are synthesized. Nanocellulose and the composites are characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, N2 and CO2 adsorption, and thermogravimetric analysis. The analyses reveal information about the crystallinity, pore structure, and thermal stability of the composites. The results show a marked development of microporosity (≈30%), which is linked mainly to the formation of a NC/UiO-66 interface, to disturbances in the UiO-66 nucleation process, and to missing cluster defects. The latter is related to the geometrical constraints of metal– organic framework (MOF) crystallization around the NC nuclei. Pore size distributions do not depend markedly on the chemistry of NC. While pores in the composites with sizes <0.5 nm are associated with the involvement of NC functional groups in the formation of MOF units, the pores with sizes >1.1 nm have their origin likely in missing linkers and missing clusters. Moreover, the surface chemistry of NC and that of the interface affects the amount of CO2 adsorbed and the strength of adsorption.
cellulose nanocrystals, CO2 adsorption, defects, isosteric heat of adsorption, metal–organic framework, porosity
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/20.500.11770/304988
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