Fundamental studies of CO₂ association with Ni(II) tetraphenylporphyrin complex

Abstract

Environmental pollution caused by CO₂ emission has been a major concern in the 21ˢᵗ century. This problem has been a big challenge for Green chemists so that they have attempted to find out solutions to reduce CO₂ level and mitigate pollution present in the atmosphere nowadays. Work related to this area mainly focuses on the synthesis of efficient catalysts to bind and reduce environmental pollutants. In this regard, we attempted to study the CO₂ binding capacity of 𝘕𝘪(𝘐𝘐)𝘵𝘦𝘵𝘳𝘢𝘱𝘩𝘦𝘯𝘺𝘭𝘱𝘰𝘳𝘱𝘺𝘳𝘪𝘯 complex since it is structurally similar to natural molecules that interact with CO₂. 𝘛𝘦𝘵𝘳𝘢𝘱𝘩𝘦𝘯𝘺𝘭𝘱𝘰𝘳𝘱𝘺𝘳𝘪𝘯 was directly synthesised using pyrrole and benzaldehyde. Purification was done by recrystallisation with dichloromethane. 𝘕𝘪(𝘐𝘐)𝘵𝘦𝘵𝘳𝘢𝘱𝘩𝘦𝘯𝘺𝘭𝘱𝘰𝘳𝘱𝘺𝘳𝘪𝘯 was synthesised using 𝘵𝘦𝘵𝘳𝘢𝘱𝘩𝘦𝘯𝘺𝘭𝘱𝘰𝘳𝘱𝘺𝘳𝘪𝘯 ligand by refluxing it with dry NiCl2 in dimethylformamide. The synthesised 𝘕𝘪(𝘐𝘐)𝘵𝘦𝘵𝘳𝘢𝘱𝘩𝘦𝘯𝘺𝘭𝘱𝘰𝘳𝘱𝘺𝘳𝘪𝘯 was characterised by using H1-NMR, UV-Visible, XRF, XRD and FT-IR spectroscopic techniques. CO₂ trapping capacity was studied with Vernier CO₂ gas sensor which is capable of measuring the transmitted amount of CO₂ from a sample. The new band appeared at 694.40 cm⁻¹ in the FT-IR spectrum after passing CO₂, indicates the formation of Ni(II)-CO₂ bond. UV-Visible and CO₂ sensor studies reveal that 𝘕𝘪(𝘐𝘐)𝘵𝘦𝘵𝘳𝘢𝘱𝘩𝘦𝘯𝘺𝘭𝘱𝘰𝘳𝘱𝘺𝘳𝘪𝘯 has higher CO₂ association capacity (99.3%) than NiCl2 and solvents (toluene : hexane (4:1 ) and water) used.