Synthesis and Photocatalytic Performance of Ni(II) Coordination Polymers for Efficient Methylene Blue Degradation

ABSTRACT Two Ni(II)‐based coordination polymers, [Ni(Hbcpt)(bpp)(H 2 O)] n ( 1 ) and [Ni 2 (Hbcpt) 2 (bpp)(H 2 O) 3 ] n ·4n(H 2 O) ( 2 ) (H 3 bcpt = 3,5‐bis(1H‐1,2,4‐triazol‐1‐yl)benzoic acid, bpp = 1,3‐bis(4‐pyridyl)propane), were hydrothermally synthesized and structurally characterized. Compound 1 exhibits a 2‐fold polycatenated 2D (4,4)‐connected layered structure, which further be organized into a 3D supramolecular framework through an interdigitated assembly mode, while compound 2 is built from dinuclear [Ni 2 (COO) 2 ( μ 2 ‐Ow)] subunits, forming a 4‐fold interpenetrated 3D framework with pcu topology. Thermal analysis confirms the stability of both frameworks before ligand decomposition. Solid‐state UV–vis spectra indicate semiconductor‐like behavior with band gaps of 3.91 eV (compound 1 ) and 3.72 eV (compound 2 ). Both compounds efficiently catalyze the photocatalytic degradation of methylene blue under UV irradiation, achieving over 96% removal within 200 min. Radical‐trapping experiments identify hydroxyl radicals (•OH) as the main active species. Moreover, the coordination polymers retain their structural integrity and catalytic performance over multiple cycles. These results demonstrate that the Ni(II)‐Hbcpt‐bpp frameworks are robust and highly effective photocatalysts for the treatment of dye‐contaminated wastewater.