Aqueous Molecular Sieving and Strong Gas Adsorption in Highly Porous MOFs with a Facile Synthesis

Aqueous molecular sieving is demonstrated in a new series of isostructural metal organic frameworks based on the perylene tetracarboxylate (PTC) ligand. The frameworks can be formed in water at room temperature with Mg, Ni, and other first row transition metal ions and adopt a highly porous topology that results in predicted surface areas of over 2000 m2 g–1 and periodic channels of around 6 Å in diameter. Unusually, the M-PTC MOFs are highly resistant to moisture and can be readily synthesized on multigram scales. The frameworks have been shown to exhibit molecular sieving in the absorption from mixtures of organic molecules at low aqueous concentrations, with an application demonstrated on a dangerous water-borne herbicide, Paraquat. Ni-PTC also exhibits a structural flexibility that leads to strong and selective gas adsorption characteristics, with an IAST selectivity of 300 for carbon dioxide being adsorbed over nitrogen. Binding enthalpies for hydrogen and carbon dioxide are also very strong in comparison to other MOFs, at 10.75 and 52.50 kJ/mol respectively.