Findings from an international research team at Tarbiat Modares University (Tehran), Bu-Ali Sina University (Hamedan), and the University of Granada (Spain) show that combining graphitic carbon nitride with a sulfur-based organic polymer can significantly enhance the efficiency of photocatalytic removal of pharmaceuticals. This photocatalytic heterostructure uses light energy to break down pharmaceuticals and emerging pollutants into less harmful compounds.
According to the Report, Contamination of surface and groundwater by pharmaceuticals and emerging compounds has become a serious public health and environmental concern in recent decades. Anti-inflammatory drugs, antibiotics, and nervous system stimulants that enter wastewater after consumption are often not fully removed in conventional treatment processes, leading to harmful effects on ecosystems and human health. The joint research indicates that a novel composite of sulfur-based polymer nanostructures with graphitic carbon nitride (CN) offers an effective and sustainable approach to photocatalytic degradation of pharmaceuticals in water.
Conventional water treatment methods, including chemical and biological filters, have limitations in removing low-concentration and chemically stable compounds. Photocatalytic technology, which accelerates oxidation reactions under solar or artificial light, provides a promising solution. However, traditional photocatalytic materials such as graphitic carbon nitride suffer from limitations in charge separation and overall efficiency. Combining CN with a sulfur-based organic polymer into a heterostructure improves performance and enhances stability.
In this study, a thiazole- and sulfur-based organic polymer was synthesized via the polymerization of tri(4-formylphenoxy)cyanurate (TFPC) with sulfur and naphthylene diamine, and subsequently combined with CN through microwave-assisted synthesis. Structural, chemical, and morphological analyses—including FTIR spectroscopy, XRD, STEM microscopy, and elemental analysis—confirmed that the resulting heterostructure provides a wide and uniform active surface. Optical and electrochemical analyses, including UV-Vis absorption, photoluminescence, electrochemical impedance spectroscopy (EIS), and transient photocurrent measurements, further verified improved charge separation and reduced unwanted recombination.
The researchers tested different polymer-to-CN ratios and found that 20 wt% polymer provided the best performance. This sample showed significantly higher degradation rates for pharmaceuticals such as acetaminophen, caffeine, antipyrine, ciprofloxacin, sulfamethoxazole, and diclofenac compared to pure CN. The 20% COF-CN heterostructure performed best under near-neutral conditions, with minimal influence from HCO₃⁻ ions, demonstrating process robustness under diverse environmental conditions.
The photocatalytic mechanism was also clarified: superoxide radicals and photo-induced holes were the main oxidative species, while hydroxyl radicals played a negligible role. Band alignment analysis confirmed a type-I heterostructure, with the sulfur-based polymer acting as an “electron reservoir,” facilitating charge separation and enhancing oxidation reactions.
This innovative composite not only delivers higher efficiency but also shows excellent stability and reusability. Tests revealed that the recovered sample maintained its crystal structure and key FTIR spectral features, making COF-CN heterostructures suitable for large-scale applications, particularly in industrial and urban water treatment.
Additionally, the metal-free microwave synthesis method overcomes limitations of traditional solvent-based approaches, offering shorter synthesis times and improved performance. With their high efficiency, good stability, and ease of synthesis, these photocatalysts can be applied in the design of photochemical reactors and next-generation water treatment systems. The researchers highlight that future progress in this field depends on reactor design and optimized material separation to fully exploit the potential of such heterostructures.