Optimizing H2, D2, and C2H2 Sorption Properties by Tuning the Pore Apertures in Metal-Organic Frameworks.

Abstract

By adjustment of the arm lengths of two triphenylamine-based ligands, two nearly isostructural metal-organic frameworks (MOFs), namely, the reported nanoporous FIR-29 (FIR = Fujian Institute of Research) and the new microporous FJI-Y9 (FJI = Fujian Institute), are obtained, and all exhibit honeycomb lattices of hexagonal channels with Ca-COO chains connected by tris[(4-carboxyl)phenylduryl]amine (H3TCPA) ligands and 4,4',4''-nitrilotribenzoic acid (H3NTB) ligands, respectively. Although the Brunauer-Emmett-Teller (BET) surface area (1117 m2 g-1) and pore size (8.5 Å) of FJI-Y9 are much lower than those (BET surface area of 2061 m2 g-1 and pore size of 16 Å) of the reported FIR-29 because of the shorter arm lengths of H3NTB, the activated FJI-Y9-ht shows high H2 (202.3 cm3 g-1) and D2 (221.9 cm3 g-1) uptake under 77 K and 1 bar and C2H2 uptake of 168.9 cm3 g-1 under 273 K and 1 bar, which are all at least 48% enhancement over those of FIR-29-ht. The above results indicate that small pores in MOFs are beneficial to the uptake of some special gases including H2, D2, C2H2, etc.