A New Anilato-based Series of 3D MOFs for Environmental Quality

Capturing CO₂ from the atmosphere represents a key challenge, since CO₂ has been recognized as the primary anthropogenic greenhouse contributor to the increase in Earth’s average temperature. Their high porosity, tunable pore size and large surface area make Metal-Organic Frameworks (MOFs) promising candidates to uptake and separate CO₂ from gaseous mixtures. In 2021, some of us synthesized, via hydrothermal approach, a new microporous MOF, formulated as [Co(trz₂An)]n·2.5H₂O (CAMOF-1), by combining 3, 6-N-ditriazolyl-2,5-dihydroxy-1,4-benzoquinone, as organic linker, with a Co^II metal node in a 1:1 stoichiometric ratio. This MOF showed a favourable balance of high selectivity, high adsorption capacity, and high regenerability, thus being a promising candidate for CO₂ gas separation processes. We report herein the synthesis, crystal structure and performance studies of three new microporous MOFs obtained by combining trz₂An with Cu^II, Zn^II and Fe^II metal nodes, formulated as [Cu(trz₂An)]^.nH₂O (CAMOF-2), Zn(Trz₂An)^.3H₂O (CAMOF-3) and Fe(Trz₂An)^. 3H₂O (CAMOF-4). CAMOF-2-4 show a 3D robust structure, with a pore size of 3.46 Å for CAMOF-2 and 3,89 Å for CAMOF-3,4, consistent with the kinetic radius of CO₂ and absorption capacity of 2 molecules of CO₂ / unit formula as confirmed by pore analysis data. Static and Dynamic Adsorption Measurements revealed i) remarkable carbon dioxide uptake, ii) high selectivity in CO₂:N₂ gas mixtures, iii) easy regeneration in mild conditions. Furthermore, i) preliminary CO₂ electroreduction studies showed a good capability of CAMOF-2 to convert carbon dioxide into ethylene and ii) adsorption test removal, performed on CAMOF-3 and CAMOF-4, revealed a good performance inremoving Cd^II, at different pH ranges and concentrations. In conclusion, trz₂An is a strategic organic linker, which combined with different transition metal ions, gave rise to a novel thermal stable, robust, microporous 3D MOFs family employing for environmental quality.