The solvothermal synthesis of a 3D rod-like Fe–Al bimetallic metal–organic-framework for efficient fluoride adsorption and photodegradation of water-soluble carcinogenic dyes

Abstract

A thermally stable, 3D rod-like, nanosized, porous, pH-stable Fe–Al bimetallic metal–organic-framework with terephthalic acid (1,4-benzenedicarboxylic acid) as a linker (abbreviated to Fe–Al BDC) with a surface area of 120.255 m² g⁻¹ was synthesized using a solvothermal method for fluoride adsorption and the photodegradation of rhodamine B (RhB)/methylene blue (MB) within a pH range of 2–11. The μ-oxo metal bonds and 3D rod-like structure of Fe–Al BDC were determined via PXRD, FTIR, Raman spectroscopy, and FESEM analyses. The relationship between the particle size and surface area obeyed the André relationship. The chemisorption of fluoride, supported by XPS and FTIR studies, obeyed pseudo-second-order kinetics, with a Langmuir/Freundlich adsorption isotherm, and thermodynamic studies were undertaken. RhB/MB (10⁻⁵/10⁻⁴ M) photodegraded under solar irradiation following pseudo-first-order kinetics. The surface–boundary-layer fluoride adsorption mechanism is confirmed based on the interparticle-diffusion model and mass-transfer model supported by ξ-potential analysis, and the mineralization mechanism of RhB was established using Kröger–Vink notation and HPLC studies; the material was reusable for up to eight cycles.