Enhanced Adsorption Selectivity of Carbon Dioxide and Ethane on Porous Metal-Organic Framework Functionalized by a Sulfur-Rich Heterocycle.
Vadim A DubskikhKonstantin Aleksandrovich KovalenkoAnton S NizovtsevAnna A LysovaDenis G SamsonenkoDanil N DybtsevVladimir Petrovich FedinPublished in: Nanomaterials (Basel, Switzerland) (2022)
Porous metal-organic framework [Zn 2 (ttdc) 2 (bpy)] ( 1 ) based on thieno [3,2-b]thiophenedicarboxylate (ttdc) was synthesized and characterized. The structure contains intersected zig-zag channels with an average aperture of 4 × 6 Å and a 49% ( v/v ) guest-accessible pore volume. Gas adsorption studies confirmed the microporous nature of 1 with a specific surface area (BET model) of 952 m 2 ·g -1 and a pore volume of 0.37 cm 3 ·g -1 . Extensive CO 2 , N 2 , O 2 , CO, CH 4 , C 2 H 2 , C 2 H 4 and C 2 H 6 gas adsorption experiments at 273 K and 298 K were carried out, which revealed the great adsorption selectivity of C 2 H 6 over CH 4 (IAST selectivity factor 14.8 at 298 K). The sulfur-rich ligands and double framework interpenetration in 1 result in a dense decoration of the inner surface by thiophene heterocyclic moieties, which are known to be effective secondary adsorption sites for carbon dioxide. As a result, remarkable CO 2 adsorption selectivities were obtained for CO 2 /CH 4 (11.7) and CO 2 /N 2 (27.2 for CO 2 :N 2 = 1:1, 56.4 for CO 2 :N 2 = 15:85 gas mixtures). The computational DFT calculations revealed the decisive role of the sulfur-containing heterocycle moieties in the adsorption of CO 2 and C 2 H 6 . High CO 2 adsorption selectivity values and a relatively low isosteric heat of CO 2 adsorption (31.4 kJ·mol -1 ) make the porous material 1 a promising candidate for practical separation of biogas as well as for CO 2 sequestration from flue gas or natural gas.