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.