Melt-based porous material and PMMA as an eco-friendly tool for the visual detection of cationic dyes in environmental fish samples.

Cationic dyes like crystal violet (CV) and methylene blue (MB) pose severe environmental and biological risks, demanding rapid, on-site detection. Conventional colorimetric methods often suffer from high detection limits and poor robustness. Metal-organic frameworks (MOFs) such as ZIF-8 show promise for dye adsorption, but integrating them into processable, transparent matrices for visual sensing remains a challenge, driving the need for advanced hybrid materials. ZIF-8 nanoparticles were synthesized and uniformly embedded within a poly (methylmethacrylate) (PMMA) matrix through a melting mix approach, yielding a transparent composite material. This ZIF-8/PMMA hybrid served as a highly effective visual sensor for the rapid detection of CV and MB in aqueous solutions. A systematic optimization of critical parameters (pH, contact time, temperature, and ionic strength) demonstrated that the sensor has robustness under diverse environmental conditions. Notably, the sensor achieved exceptional visual detection limits of 0.1 mg L-1 (CV at 583 nm) and 0.08 mg L-1 (MB at 664 nm), surpassing conventional colorimetric methods. Density functional theory (DFT) calculations revealed that van der Waals interactions dominated the adsorption mechanism between ZIF-8 and the target dyes. When applied to fish tissue samples, the method exhibited excellent accuracy (recovery rates: 92-107 %) and reproducibility (RSD: 8.9-12.8 %), with a strong linear response (R2 > 0.99) for both analytes. The selective adsorption performance of ZIF-8 combined with the optical transparency and processability of PMMA provides a groundbreaking environmental protection platform for on-site monitoring of cationic dyes in complex biological matrices.