Rational design of carbon materials with tailored pore structure for efficient separation of CH4/N2 mixture

Abstract

The highly-efficient separation of CH4/N2 mixture on carbon materials is significantly hindered by the inherent trade-off that exists between CH4 adsorption capacity and CH4/N2 separation selectivity. Herein, we have constructed a type of novel carbon materials (PGC-x) with well-controlled ultramicropores ranging from 0.48 to 0.57 nm for CH4/N2 separation. The Zn-based salt template was in-situ confined into the polymer framework during the co-assembly of phloroglucinol and glyoxylic acid. The subsequent evaporation of Zn at high temperature gives rise to the adjustable ultramicropore structure, effectively devoid of mesopores and macropores. Benefiting from the optimal pore size of 0.50 nm, PGC-1 demonstrated high CH4 uptake of up to 1.50 mmol/g. Meanwhile, the CH4/N2 (15/85 and 85/15, v/v) separation selectivity of PGC-1 at 298 K and 1.0 bar reached 5.8 and 6.0, respectively. Dynamic breakthrough experiments proved that PGC-1 could be used as efficient adsorbent for capturing low or high concentration of CH4 from N2. This work offers a promising design principle for optimizing porous structure of carbon materials, with the aim of minimizing the selectivity-capacity trade-off that often arises in the separation of diverse gas pairs.