Impact of decoration of spherical silicon nanoparticles on 2D Ni-MOF nanosheets for integrating superior photodegradation of toxic organic pollutants in aqueous solution.

The contamination of water resources by toxic organic pollutants poses severe environmental and health risks, representing a critical global challenge that demands the development of efficient, cost-effective, and sustainable remediation strategies. Herein, we report a scalable synthesis of a novel photocatalyst consisting of two-dimensional (2D) nanosheets of a nickel-based metal-organic framework (Ni-MOF) in conjunction with low-bandgap silicon nanoparticles (Si-NPs). The Si-NPs of an average diameter of 7.42 nm was developed using an economical method from locally available sand. The impregnated Si-NPs onto the Ni-MOF nanosheets using a green approach affording bandgap engineering. The results indicate that highly pure Si-NPs was successfully developed in scalable quantity from locally available sand. Various mass loadings in the range of 1-7.5 wt% of developed Si-NPs were decorated on the surface of Ni-MOF nanosheets yielding new nanophotocatalysts recording bandgap of 2.68 eV and achieving reduction by ~ 50% compared to Ni-MOF sheets free Si-NPs. The attained photocatalysts were then exploited for photocatalytic degradation of various organic pollutants, including Malachite Green (MG), Crystal violet dye (CV), and Tetracycline (TC) and demonstrated excellent degradation efficacy. The photocatalytic degradation of MG, CV, and TC, achieving degradation efficiencies of 91.7%, 86.8%, and 95.2%, respectively, representing a significant enhancement compared to silicon-free Ni-MOF (MG: 45.8%, CV: 39.6%, TC: 44.6%). Photocatalytic degradation factors such as initial organic pollutant concentration, pH, catalyst dose, reaction time, and temperatures were also studied. Importantly, the adsorption isotherms, kinetics, and thermodynamic parameters were also investigated. The biological phytotoxicity study shows no significant differences of plant height between the plants irrigated with regular water (19.90 ± 1.7 cm) and those irrigated with water treated with the developed photocatalyst (18.86 ± 2.92 cm) in comparison to polluted water irrigate plant (14.49 ± 2.10 cm). Additionally, the antimicrobial study confirmed the inhibitory actions against bacterial strains, achieving antibacterial inhibition zone of 47.7 mm and 30 mm, against S. aureus and E. coli, respectively. Interestingly, the reusability and economic feasibility indicates that the developed catalyst can be reused efficiently for up to 5 cycles without significant decrease in photocatalyst efficiency and cost of photocatalyst, which is sufficient for treating approximately 20 m of wastewater efficiently, is about $154.50, respectively.