| 초록 |
The 'molecular sieving effect' of zeolites has enabled size-selective adsorption and catalysis. Although a large variety of zeolites have been developed, it is still challenging to find zeolites that can separate molecules such as CO2, N2, CH4 and small organics that have kinetic diameters all closely located in the range of 0.3 – 0.4 nm. Here we demonstrate that controlled collapse or atomic disordering of NaA zeolite can systematically narrow the effective pore size below 0.4 nm. In zeolite chemistry, it has been known that full decationization (i.e., replacing extra-framework Na+ cations with H+) of highly aluminous zeolites (Si/Al ~ 1.0) results in a complete loss of zeolite crystallinity. However, the phenomenon has not been carefully investigated due to a lack of scientific interests in such ill-defined materials. As the zeolite is gradually disordered, the adsorption amounts for all gas molecules decrease; however, larger molecules show a much faster decrease than that of the smaller ones. Consequently, the adsorption selectivities could be remarkably enhanced for various gas pairs. |
