Aerogels of Cellulose Nanofibers@Metal-Organic Frameworks for Carbon Dioxide Capture

Abstract

In this study, three carboxylic acid-functionalized metal-organic framework (MOF) materials (UiO-66, UiO-66-COOH, and UiO-66-2COOH) were synthesized using renewable cellulose aerogel (CA). A composite adsorbent (UiO-66-X/CA), characterized by a high specific surface area, abundant active sites, and excellent structural stability, was successfully developed. Under the conditions of 273K and P/P0 = 0.1, GCMC simulations show that in the UiO-66 series of materials, an increase in the number of carboxylic acid modifications leads to an increase in CO2 adsorption capacity, as well as an increase in the types and strengths of interaction forces. The regulatory mechanism of functional groups on CO2 adsorption performance was systematically investigated. The incorporation of carboxylic acid groups significantly enhanced the CO2 affinity of the composite material. The study investigated the loading amounts of three different MOFs and found that a 100% loading ratio exhibited the optimal CO2 adsorption performance. At 273K and 1 bar, the CO2 adsorption capacity of UiO-66-2COOH/CA with 100% loading reached 31.7 cm3/g, attributed to the synergistic effect of the dicarboxylic acid group. Based on the Ideal Adsorbed Solution Theory (IAST), gas separation performance was predicted according to the flue gas composition (CO2: N2 = 15:85). Carboxyl-modified MOFs demonstrated superior selectivity for carbon dioxide adsorption, with a maximum value of 41.9. The breakthrough experiment further proved that UiO-66-COOH/CA exhibited selective adsorption capacity for CO2/N2 under both dry and wet conditions. Moreover, the hierarchical pore structure of cellulose aerogel effectively enhanced CO2 diffusion kinetics. This study elucidates the co-optimization of CO2 adsorption performance through MOF functionalization and porous carriers, providing a strategy for the development of scalable and bio-based carbon capture materials. Additionally, the integration of cellulose aerogel addressed the processing challenges of MOF powders, offering new insights into the practical application of MOF materials.