Iodine adsorption by Thiophene-Based Covalent Organic Polymer: A Study of Structural Influence on Performance
Abstract
A novel covalent organic polymer (COP) derived from Tris (4-aminophenyl) amine (TPA) and 4,4'-(thiophene-2,5-diyl) dibenzaldehyde (T) moieties was constructed and synthesised (TPAT-COP). The synthesised polymer has been successfully characterised by FT-IR, ¹³C CP-MAS NMR, and surface (e.g., BET, SEM) studies with the surface area (1199 m² g⁻¹) and a microporous nature with a mean pore diameter of 1.54 Ao. Further, TGA analysis shows an extraordinary stability of the material even at high temperature. In accompanying this, TPAT-COP exhibits an exceptionally high iodine (I₂) adsorption capacity (467 wt%) in the vapour phase and is on par with or even surpasses that of the most advanced thiophene-based COPs. These results are the outcome of the meticulous design of the polymer embedded with sulphur sites and covalent bridges that can counterbalance the low surface area and pore volume. Indeed, FT-IR, XPS, and morphological data supported with computational results outline the higher affinity of the S atom in the thiophene ring and the N atom in the imine linkage towards iodine. The higher affinity of TPAT-COP towards iodine has been theoretically evaluated by observing strong binding energy in DFT calculations. The outcomes were compared with organometallic-based COP (DAPA-COP) to validate that the introduction of the thiophene unit has significantly improved the adsorption capacity of iodine. As a result, a remarkably high retention rate and reversibility were achieved. Thus, a simple, cost-effective design and strategy defined the synthesised COP as a viable tool for rapid I₂ adsorption.