Enhanced gas separation performance of an ultramicroporous pillared-layer framework induced by hanging bare Lewis basic pyridine groups

Abstract

Pillared-layer metal–organic frameworks show great promise for gas storage and separation because their pore size as well as functionality usually can be controlled and adjusted synergistically. By combining the common pyridine and carboxylate groups, we design herein a new 3D pillared-layer framework, [Co₂(DBPT)(BPY)₂(CO₃)]_n (SNNU-95). Dinuclear [Co₂] motifs are connected by DBPT ligands to form a 2D layer, which is further bridged by BPY to obtain the 3D pillar-layered framework of SNNU-95. Remarkably, two un-coordinated pyridine groups of DBPT not only help stabilize the 2D layer through π⋯π stacking but also point into the 1D channels to create an ultramicroporous environment. Taking advantage of the ultramicroporosity and pyridine Lewis basic sites, SNNU-95 shows not only extra high CO₂ over CH₄ and C₂ hydrocarbons over CH₄ selectivity, but also remarkable C₂H₂/CO₂, C₂H₂/C₂H₄, and C₂H₄/CO₂ separation under ambient conditions. This synergistic effect resulting from functional groups and pore size provides a promising route to design porous materials for the highest possible gas uptake and separation performance.