2D copper-isophthalate MOFs: Highly selective CO₂ conversion with experimental and theoretical investigations

Two dimensional (2D) copper-carboxylate frameworks (MOFs) have become increasingly important in modern science and technology due to their unique properties broad-spectrum applications. Two 2D Cu-isophthalate frameworks (Cu-MOF1 and Cu-MOF2) were synthesized via solvothermal and ambient-condition synthetic methods, respectively, employing the relatively less-explored isophthalic acid linker. Multiple analytical techniques (FTIR, TGA, PXRD, SEM-EDX, and BET) were applied for characterization of synthesized materials. Single crystal X-ray diffraction (SC-XRD) analysis confirmed the SBUs self-assembled structure resulted nanosized bowls which in turn form 2D MOF layers. Considering the interesting structural characteristics and facile bulk scale synthesis of Cu-MOF, it was selected as a potential catalyst for the chemical fixation of CO₂ with epichlorohydrin (ECH) to produce the corresponding cyclic carbonate. A comprehensive optimization of the reaction parameters, including temperature, CO₂ pressure, reaction time, catalyst and/or co-catalyst loading, was performed for achieving maximum ECH conversion. The chemical fixation of CO₂ to epoxide revealed promising catalytic efficiency of Cu-MOF: with ⁓97% conversion and > 99% selectivity to organic cyclic carbonate at room temperature to 120 °C under 1–3 bar gas pressure for 3–24 h by applying ~0.3 mol% catalyst and ~0.1 mol% co-catalyst. The scope of the epoxides was extended for assessing the catalytic potential of Cu-MOF towards five different substrates. Theoretical investigations revealed interesting energy profiling for efficient conversion of CO₂. The structural stability of Cu-MOF was investigated by performing post-catalytic characterizations (SEM, PXRD, TGA). 2D Cu-MOF appeared to be a promising catalyst for valorization of CO₂ in production of valued cyclic carbonates.