Metal-organic frameworks with a sulfur-rich heterocycle: synthesis, gas adsorption properties, and metal exchange

Three new three-dimensional (3D) metal-organic frameworks [M 2 (ttdc) 2 (dabco)] (M = Zn( ii ), 1-Zn ; Cu( ii ), 1-Cu ; and Zn/Cu, 1-ZnCu ) based on thieno[3,2- b ]thiophene-2,5-dicarboxylate (ttdc 2− ) were synthesized and characterized by a combination of physicochemical methods (single crystal X-ray diffraction, powder X-ray diffraction, chemical and thermogravimetric analyses and IR spectroscopy). 1-Cu demonstrated permanent porosity ( V pore = 0.790 cm 3 g −1 and S BET = 1725 m 2 g −1 ) and significant CO 2 , CH 4 , C 2 H 2 , C 2 H 4 and C 2 H 6 gas uptakes under ambient conditions. The adsorption selectivities for gas mixtures, calculated by IAST, were 10.8 (10.7), 14.6 (9.4), 1.7 (1.6) and 1.5 (1.6) for the equimolar gas mixture compositions CO 2 /N 2 , C 2 H 6 /CH 4 , C 2 H 6 /C 2 H 4 and C 2 H 6 /C 2 H 2 at 1 bar and 273 K (298 K), respectively. The mixed-metal compound 1-ZnCu was prepared by a crystal-to-crystal ion exchange metathesis reaction from 1-Zn with a 52% degree of ion substitution, confirmed by energy-dispersive X-ray spectroscopy, optical microscopy and single crystal X-ray diffraction analysis. Three new 3D metal-organic frameworks [M 2 (ttdc) 2 (dabco)] (M = Zn( ii ), 1-Zn ; Cu( ii ), 1-Cu ; and Zn/Cu, 1-ZnCu ) based on thieno[3,2- b ]thiophene-2,5-dicarboxylate (ttdc 2− ) were synthesized and characterized by a combination of physicochemical methods.