Two Microporous Metal–Organic Frameworks with Suitable Pore Size Displaying the High CO2/CH4 Selectivity

Two microporous metal–organic frameworks, [Zn 2 (HDDCBA)]·2DMF·2H 2 O ( 1 ) and [Cd 2 (DDCBA)·DMA·H 2 O]·H 2 N(Me) 2 ( 2 ) have been synthesized under solvothermal condition by using a less-exploited symmetrical pentacarboxylate ligand, 3,5-di(3′, 5′-dicarboxylphenyl)benozoic acid (H 5 L). Both compounds 1 and 2 reveal the (5,5)-connected nets based on the binuclear metal clusters and organic linkers. The desolvated structure of 1 ( 1a ) contains two shapes of 1D channel with suitable pore size and polar system decorated by uncoordinated carboxylate groups. As a result, 1a possesses not only high CO 2 loading but also excellent CO 2 /CH 4 selectivity at 273 and 298 K. In addition, both compounds display solid-state luminescence stemming from the ligand-centered fluorescence of H 5 L.