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

Two microporous metal–organic frameworks, [Zn2(HDDCBA)]·2DMF·2H2O (1) and [Cd2(DDCBA)·DMA·H2O]·H2N­(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 (H5L). 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 CO2 loading but also excellent CO2/CH4 selectivity at 273 and 298 K. In addition, both compounds display solid-state luminescence stemming from the ligand-centered fluorescence of H5L.