Precise pore size modulation of K-MER zeolites for N2 trapping.

[Display omitted] • Pure-phase K-MER with controllable Si/Al ratios were synthesized. • The control of the Si/Al ratio enabled precise regulation of the pore size on the sub-angstrom scale. • K-MER-2.7 showed a hindering effect on CH 4 and exhibited outstanding N 2 /CH 4 selectivity. • Breakthrough experiments confirmed the practical feasibility of zeolite separation of N 2 /CH 4 mixtures for the first time. The separation of nitrogen (N 2) and methane (CH 4) is a difficult challenge in the field of natural gas purification, especially the removal of small amounts of N 2. Here, we have successfully developed a series of pure-phase MER zeolites with controllable Si/Al ratios, showing different N 2 trapping effects through an oxalic acid-assisted synergistic fast dynamic crystallization strategy. Among them, K-MER-2.7 showed the most remarkable result, with an N 2 adsorption capacity of up to 0.48 mmol g−1 at 273 K, and an N 2 /CH 4 uptake ratio greater than 10. This was attributed to a narrowing of the pores to form ultra-micropores that limited the uptake of larger sized CH 4 , leading to excellent N 2 /CH 4 selectivity (85.6). Adsorption kinetic experiments and molecular dynamics simulations corroborated the severe hindering effect towards CH 4. Breakthrough experiments with a variety of feed gas compositions at different flow rates confirmed the practical feasibility of applying K-MER-2.7 to separate N 2 /CH 4 gas mixtures. [ABSTRACT FROM AUTHOR]