Facile in-situ growth of metal-organic framework layer on carboxylated nanocellulose/chitosan aerogel spheres and their high-efficient adsorption and catalytic performance

A core-shell hybrid aerogel sphere material was successfully fabricated by a combined assembly strategy of ionic cross-linking and coordination bonding. The MOF199 crystal shell was in-situ grown on the surface of Cu2+ ions cross-linked carboxylated cellulose nanocrystals (CNCA) and carboxymethyl chitosan (CMCS) hydrogel sphere templates at room temperature for a short time, and the aerogel spheres (MOF-199@CNCA/CMCS) were obtained after freeze-drying treatment. The pH value of 1,3,5-benzenetricarboxylic acid ligand solution is crucial for the high coverage of MOF-199 shell layer on the CNCA/CMCS cores. And CNCA and CMCS plays a cooperative role in forming the stable aerogel core. The changing morphology of MOF-199 with the evolution of {1 1 1} crystallographic plane was found by adjusting the concentration of components and reaction time. The nitrogen sorption isotherm and pore size distribution confirmed the mesopores and macropores structure of MOF-199@CNCA/CMCS aerogel spheres. Consequently, the obtained aerogel spheres exhibited an excellent adsorption capacity towards methylene blue (MB) up to 1112.2 mg.g(-1). The adsorption equilibrium of MB was suggested as multilayer adsorption based on the Freundlich isotherm model. The carbonization product Cu/ CuO/Cu2O@C of hybrid aerogels was proved as a high-efficient catalyst for the reduction of p-nitrophenol(4-NP). The catalytic rate constant can reach 21.23 x 10(-3) s-1. And the CuO species plays a dominant role in catalyzing the reduction of 4-NP.

Automated summary

A core-shell hybrid aerogel sphere material was fabricated by combining ionic cross-linking and coordination bonding strategies, with MOF199 crystal shell grown on Cu2+ ions cross-linked CNCA and CMCS hydrogel sphere templates. The resulting aerogel spheres exhibited mesoporous and macroporous structure and excellent adsorption capacity for methylene blue. Moreover, the carbonization product of hybrid aerogels showed high efficiency as a catalyst for the reduction of p-nitrophenol, with CuO species playing a dominant role in the catalytic process.