Coordinatively Unsaturated Structurally Diverse Homophthalate-Based Cobalt(II) Coordination Polymers for Efficient Multicomponent Catalysis

Coordination polymers (CPs) have emerged as pioneering compounds due to their diverse structural features and tunable properties. Numerous structural advantages, along with thermal and chemical stability, make CPs promising materials for various applications, preferably in catalysis. Herein, four CPs [Co(4-ABPT)(HPA)(H2O)], SSICG-8; [Co(4-ABPT)(HPA)(H2O)]·4H2O, SSICG-9; [Co(BPY)(HPA)(H2O)(CH3OH)], SSICG-10; and [Co(4-ABPT) (HHPA)2]·H2O, SSICG-16 (SSICG stands for solid-state and inorganic chemistry group, 4-ABPT = 3,5-di(pyridine-4-yl)-4H-1,2,4-triazol-4-amine, H2HPA = homophthalic acid, and BPY = 4,4′-bipyridine) have been synthesized via the hydrothermal synthetic methodology. SSICG-8 showcases a 4,4-net topology with a Schläfli symbol of 44.62, while SSICG-10 displays a 3,3-net topology. Herein, we have tuned the catalytic performance by tuning the Lewis acidic open metal sites (OMSs), Lewis basic sites, and porosity of the compounds. Activated SSICG-8 and SSICG-9 have Lewis acidic open metal sites (OMSs) and basic free amine and pyridyl groups. The presence of Lewis acidic high-density OMSs, free basic amine groups, and porosity makes SSICG-9 an efficient catalyst, whereas SSICG-8 lacks porosity, SSICG-10 lacks basic sites, and SSICG-16 lacks OMSs. These structural features were clearly visible in the observed catalytic efficiency order of SSICG-16 < SSICG-10 < SSICG-8 < SSICG-9. The most efficient catalyst, SSICG-9, was employed to synthesize Nemadipine B (1,4-dihydropyridine-based drug) with a 95% yield at 60 °C, using only 1.5 mol % within 4 h in ethanol. This study presents a systematic strategy for synthesizing coordination polymers and showcasing their efficacy in catalysis under mild and environmentally friendly conditions.