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Micro- and Ultramicroporous Polyaminals for Highly Efficient Adsorption/Separation of C1-C3 Hydrocarbons and CO2 in Natural Gas.

This paper presents a series of micro- and ultramicroporous polyaminals with BET surface areas up to 1304 m2 g-1, which are prepared from two triazine-based tetraamines and three dialdehydes or monoaldehyde through the A4 + B2 or A4 + B1 aminalization reaction. It is interesting to find that the para-substituted monomers are favorable to force the linking struts apart in the network to generate micropores (1.22 nm), whereas the meta-substituted monomers make the pores in the network squeezed by the twisted linking struts, resulting in the formation of ultramicropores (0.52 nm). Besides, the adsorption behaviors of the major components of natural gas, such as propane (C3H8), ethane (C2H6), methane (CH4), and carbon dioxide (CO2), are significantly different, strongly depending on the polarizabilities, critical temperatures, molecular sizes of gases, porosity parameters of polymers, and the interaction between gases and the polymer skeleton. At 298 K/1 bar, the polymers show high uptake for C3H8 (114.5 cm3 g-1) and C2H6 (84.2 cm3 g-1). Moreover, the adsorption selectivities of C3H8/CH4, C2H6/CH4, C3H8/C2H6, C3H8/CO2, C2H6/CO2, and CO2/CH4 also reach 296.3, 23.1, 9.0, 22.1, 4.1, and 5.0, respectively, exhibiting promising applications in adsorption/separation of C1-C3 hydrocarbons and stripping CO2 gas from natural gas under the ambient condition.