Unprecedented High Temperature CO₂ Selectivity and Effective Chemical Fixation by a Copper-Based Undulated Metal–Organic Framework

Post- and precombustion CO₂ capture and separation are the vital challenges from industrial viewpoint, as the accessible technologies are not cost-effective and cumbersome. Thus, the development of functional metal–organic frameworks (MOFs) that are found to be promising materials for selective CO₂ capture, separation, and conversion is gaining an importance in the scientific world. Based on the strategic design, a new functionalized triazine-based undulated paddle-wheel Cu-MOF (1), {[Cu­(MTABA)­(H₂O)]·4H₂O·2EtOH·DMF}_n (where, H₂MTABA = 4,4′-((6-methoxy-1,3,5-triazine-2,4-diyl)­bis­(azanediyl))­dibenzoic acid), has been synthesized under solvothermal conditions and fully characterized. MOF 1 contains a one-dimensional channel along the a-axis with pore walls decorated with open metal sites, and multifunctional groups (amine, triazine, and methoxy). Unlike other porous materials, activated 1 (1′) possesses exceptional increment in CO₂/N₂ and CO₂/CH₄ selectivity with increased temperature calculated by the ideal adsorbed solution theory. With an increase in temperature from 298 to 313 K, the selectivity of CO₂ rises from 350.3 to 909.5 at zero coverage, which is unprecedented till date. Moreover, 1′ behaves as a bifunctional heterogeneous catalyst through Lewis acid (open metal) and Brönsted acid sites to facilitate the chemical fixation of CO₂ to cyclic carbonates under ambient conditions. The high selectivity for CO₂ by 1′ even at higher temperature was further corroborated with configurational bias Monte Carlo molecular simulation that ascertains the multiple CO₂-philic sites and epoxide binding sites in 1′ to further decipher the mechanistic pathway.