The assembly of thiophene-based bis-pyridyl-bis-amide CoII coordination polymers and their polypyrrole-functionalized hybrid materials for boosting their photocatalytic performances

Abstract

Herein, a series of multifunctional Co^II coordination polymer (CP) materials, which were based on a new semi-rigid thiophene-containing bis-pyridyl-bis-amide N,N′-bis(pyridine-3-yl)thiophene-2,5-dicarboxamide (3-bptpa) ligand and different polycarboxylates, namely, [Co(3-bptpa)(1,3-BDC)]·2H₂O (CP1), [Co(3-bptpa)(5-MIP)]·2H₂O (CP2), [Co(3-bptpa)(1,3,5-HBTC)] (CP3), [Co(3-bptpa)(5-NIP)]·2H₂O (CP4) and [Co(3-bptpa)(1,3-BDC)]·2H₂O (CP5) (1,3-H₂BDC = 1,3-benzenedicarboxylic acid, 5-H₂MIP = 5-methylisophthalic acid, 1,3,5-H₃BTC = 1,3,5-benzenetricarboxylic acid, 5-H₂NIP = 5-nitroisophthalic acid) and their polypyrrole (PPy)-functionalized hybrid materials PPy/CPn (n = 1, 2, 3, 4, 5), have been prepared. The CP materials were structurally characterized by single-crystal X-ray diffraction analyses, IR spectra, UV-vis diffuse-reflectance spectra (DRS), powder X-ray diffraction (PXRD) and thermal gravimetric analyses (TG). The structural analyses indicate that CP1–CP4 reveal similar 2D networks. CP5 exhibits a 2-fold interpenetrating 3D α-Po framework. The PPy-functionalized CP1–CP5 hybrid materials PPy/CPn were fabricated by the combination of micro-size CP particles and PPyvia a facile in situ chemical oxidation polymerization process under the initiation of ammonium persulfate (APS). The photocatalytic properties of CP1–CP5 and PPy/CPn hybrid materials have been investigated in detail. As a result, after being decorated with PPy, the photocatalytic properties of the hybrid materials, particularly PPy/CP3, have been observably enhanced for the degradation of methylene blue (MB) under visible light irradiation.