Synthesis and structure of a 3-fold Interpenetrated bifunctional Co-MOF for efficient photocatalytic degradation of safranin T and adsorptive removal of methyl orange

This study reports the solvothermal synthesis of a novel Co(II)-based metal-organic framework, namely [Co(L)(bibp)·0.5H₂O]n, constructed from 4′-(4-carboxylphenoxy)-4-biphenyl carboxylic acid (H₂L) and 4,4′-bis(imidazolyl)biphenyl (bibp), which displays an uncommon three-dimensional 3-fold interpenetrated framework based on 6⁵·8 topology. The structural characteristic and stability of Co-MOF were characterized by SCXRD, PXRD, FT-IR, TGA, SEM, BET and UV-vis DRS. The obtained Co-MOF demonstrates excellent stability and dual functionality for the removal of organic dye pollutants via adsorption and photocatalysis. It exhibited outstanding selective adsorption performance for the anionic dye methyl orange (MO), with a high capacity of 208.1 mg·g^-1. The adsorption process, which was optimized by examining kinetics, isotherms, and thermodynamics, was found to be spontaneous and predominantly physical, following the pseudo-first-order and Langmuir models. Furthermore, Co-MOF possessed remarkable photocatalytic activity for degrading the cationic dye safranine T (ST), achieving 98.67 % degradation within 80 min under UV light and maintaining high efficiency over multiple cycles. Radical trapping experiments identified superoxide radicals (·O_2^-) as the primary active species. This work confirms that the designed Co-MOF is a robust and multifunctional material capable of integrating both adsorption and photodegradation for the efficient remediation of complex wastewater.