Original Contribution to the Chemistry of Coordination Polymers Derived from Nigerian Plant-Based Linkers: Synthesis, Characterisation, and Multifunctional Applications

Coordination polymers are an emerging class of crystalline materials with tunable porosity and multi-functional applications in gas storage, catalysis, and sensing, yet their synthesis from naturally derived, regionally available organic linkers remains an open frontier in coordination chemistry. This dissertation makes original contributions to the synthesis and characterisation of novel coordination polymers using carboxylate and nitrogen-donor ligands derived from gallic acid, ellagic acid, and caffeine, which are extractable from tannin-rich plant materials abundantly available in Nigeria. Ligand isolation and purification were achieved by preparative HPLC, and structural elucidation was performed by multinuclear NMR, mass spectrometry, and single-crystal X-ray diffraction. Coordination polymers were synthesised solvothermally with cobalt(II), nickel(II), copper(II), and zinc(II) metal centres. Structural characterisation employed synchrotron powder X-ray diffraction, thermogravimetric analysis, and variable-temperature studies. Applications investigated include selective carbon dioxide over methane uptake, Lewis acid catalysis of the Knoevenagel condensation reaction, and luminescence-based sensing of nitroaromatic compounds as explosives simulants. Fifteen novel crystal structures were determined, contributing new entries to the Cambridge Structural Database. The copper-ellagic acid framework exhibited a carbon dioxide-methane selectivity of 8.3 at 298 Kelvin and 1 bar. The cobalt-gallic acid polymer showed excellent Knoevenagel catalytic activity with turnover frequencies exceeding 120 per hour. Three frameworks displayed selective quenching luminescence responses to 2,4-dinitrotoluene at sub-micromolar concentrations. This dissertation establishes coordination polymer synthesis from Nigerian-origin ligands as a productive and original research domain with practical application relevance. Keywords: coordination polymers, plant-derived linkers, crystal engineering, gas adsorption, luminescence sensing