A graphene organic framework based on a thiadiazole ligand (GOF-TDA): a good adsorbent for iodine uptake and antibacterial activity

Abstract

In the current study, a graphene organic framework (GOF-TDA) was successfully synthesized under mild conditions by cross-linking nanosheets of graphene oxide (GO) with 5-(4-nitrophenyl)-1,3,4-thiadiazol-2-amine (TDA) as the pillaring agent. The characterization of GOF-TDA has been conducted using various techniques, including FT-IR spectroscopy, FE-SEM, EDX, PXRD, TGA, and BET methods. The oxygenic functional groups in GO, the nitrogen atom in the amide groups, and the sulfur of the thiadiazole ring in TDA give mesoporous GOF-TDA a strong affinity for iodine molecules. This affinity occurs due to the formation of charge-transfer complexes between the host framework's oxygen, nitrogen, and sulfur atoms and the guest iodine molecules. Therefore, GOF-TDA demonstrated a high adsorption capacity of 835.2713 mg g⁻¹ for uptaking iodine from a cyclohexane solution. Additionally, GOF-TDA also exhibited exceptional chemical, thermal, and structural stability towards iodine, with an excellent capacity of 153 wt% for volatile iodine. To the best of our knowledge, rare studies have specifically examined iodine uptake using a GOF constructed with a sulfur-based ligand, highlighting the importance of our research. This study also aimed to investigate the antibacterial properties of GOF-TDA (10 mg mL⁻¹) against four species of bacteria, including two Gram-positive (Bacillus subtilis and Staphylococcus aureus) and two Gram-negative (Escherichia coli and Pseudomonas aeruginosa). The results indicated that GOF-TDA was effective against all bacterial species, with noticeable growth inhibition in Gram-positive bacteria. Moreover, GOF-TDA demonstrated impressive growth inhibition and multiplication against two other Bacillus species, Bacillus tequilensis strain (T28) and Priestia endophytica (T25), from the initial hours of treatment as indicated by time-kill kinetic studies. Our study paves the way for the development of metal-free, eco-friendly, cost-effective, and stable multifunctional GOFs to meet critical needs in environmental protection and public health.