Selective adsorption behaviours of MOFs@SiO2 with different pore sizes and shell thicknesses.

MOF-5@SiO 2 and IRMOF-10@SiO 2 with different pore sizes and shell thicknesses were synthesized by a layer-by-layer method and used to explore the effects of pore size on dye adsorption behaviour. The characterization results indicated that shell thickness could dramatically influence pore structure. Mesopores and macropores in MOFs@SiO 2 existed when the synthetic cycles were less than 10, while micropores could be obtained when MOFs@SiO 2 were prepared after 20cycles. The adsorption kinetic and isotherm results showed that adsorption of basic fuchsin onto MOF-5@SiO 2 increased but the adsorption capacities decreased with increasing shell thickness. The adsorption rate of basic fuchsin on IRMOF-10@SiO 2 was lower and the adsorption capacity was higher than that of MOF-5@SiO 2. Meanwhile, the adsorption rates of IRMOF-10@SiO 2 decreased, but the capacities increased as the shell thickness increased. Moreover, Fourier transform infrared and X-ray photoelectron spectroscopy were used to investigate possible adsorption mechanisms. The results suggested that basic fuchsin could enter the pores of IRMOF-10@SiO 2 but could not enter MOF-5@SiO 2 due to the size-exclusion effect. The illustration of BF adsorption modes in MOF-5@SiO 2 and IRMOF-10@SiO 2 and their adsorption performance at different shell thickness. Image 1 • Preparation of MOFs@SiO 2 using layer-by-layer method. • Shell thickness plays a crucial role in morphology & pore structures of MOFs@SiO 2. • Regulation of shell thickness MOFs@SiO 2 to improve capacity and selectivity. • Size exclusion effect was a key factor which effect the adsorption behaviour. • Electric charge effect, benzene ring of IRMOF-10@SiO 2 provided interaction sites. [ABSTRACT FROM AUTHOR]