Abstract
The ZIF-8 crystals were successfully postsynthetically modified using methylamine (MA), ethylenediamine (ED), and N, N [Formula: see text]-dimethylethylenediamine (MMEN) to improve their adsorption performance toward CO2. Results showed that, compared with the original ZIF-8, the BET specific surface area of MA-ZIF-8, MMEN-ZIF-8, and ED-ZIF-8 has increased by 118.2%, 92.0%, and 29.8%, respectively. In addition, their total pore volume increased separately by 130.8%, 100%, and 48.7%. The adsorption capacities of CO2 on the amine-modified ZIF-8 samples followed the order [Formula: see text]. The CO2 adsorption capacities at 298 K on MA-ZIF-8, MMEN-ZIF-8, and ED-ZIF-8 were increased by 118.2%, 90.2%, and 29.8%, respectively. What is more, the CO2/N2 selectivities calculated using an IAST model of the amine@ZIF-8 samples at 0.01 bar and 298 K were also significantly improved and followed the order [Formula: see text], which increased by 173.0%, 121.4%, and 22.6%, respectively. The isosteric heat of CO2 adsorption ([Formula: see text]) on the MA-ZIF-8, MMEN-ZIF-8, and ED-ZIF-8 all becomes higher, while [Formula: see text] of N2 on these samples was slightly lower in comparison with that on the ZIF-8. Furthermore, after six recycle runs of gravimetric CO2 adsorption-desorption on MA-ZIF-8, the adsorption performance of CO2 is still very good, indicating that the MA-ZIF-8 sample has good regeneration performance and can be applied into industrial CO2 adsorption and separation.
Highlights
Nowadays, the rising level of carbon dioxide in the atmosphere has become one of the biggest problems worldwide
The postsynthetic modification route is demonstrated in Scheme 1
The as-synthesized ZIF-8 material was successfully modified with methylamine, ethylenediamine, and N, N ′-dimethylethylenediamine by using a postsynthetic method to enhance its adsorption capacity and selectivity toward CO2
Summary
The rising level of carbon dioxide in the atmosphere has become one of the biggest problems worldwide. Reducing carbon dioxide emission has been proposed to be a scientific challenge of the highest order and has been explored by many researchers throughout the world utilizing different technologies [4,5,6,7]. Among these technologies, chemical absorption with aqueous organic amines like diethanolamine (DEA) has been widely used for CO2 capture from industrial waste gases for some time, but they are still subject to volatilization or degradation of organic amines, instrument corrosion, and high energy consumption for solvent regeneration [8,9,10]. Owing to their diverse framework structure, high crystallinity, large surface area, and unlimited adjustability of pore structures and surface functionalities, MOFs exhibit great application prospects in the field of Adsorption Science & Technology
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