Water-Stable Zn(II) Coordination Polymers Regulated by Polysubstituted Benzenes and Their Photocatalytic Performance toward Methylene Blue Degradation Dominated by Ligand-Field Effects

Abstract

Photodegradation of organic dyes over coordination polymer (CP) photocatalysts has become one of the effective strategies for the prevention and control of water pollution, in which the energy band structures manipulated by the ligand field of the catalytically active metal play extremely vital roles in enhancing the photocatalytic activity. To better rationalize the ligand-field function on the band structure, a series of six 2,4,6-tris­(4-pyridyl)-1,3,5-triazine (tpt)-based Zn­(II)-CPs have been hydrothermally prepared by transforming the types, numbers, and locations of the coordinative substitutes attached on benzene. All of these Zn­(II)-CPs have been fully structurally and photophysically characterized and used as photocatalysts for methylene blue (MB) decontamination by UV light illumination. Single-crystal structural analyses reveal that isomeric 1,2,4 (H3L1)- and 1,3,5-benzenetricarboxylates (H3L2) have assembled the ternary system into the gridlike framework {[Zn­(tpt)­(HL1)]·H2O} n (1), ribbon-to-connector aligned sheet [Zn3(H2O)­(tpt)2(L1)2] n (2), and hexagonal dimer based double layer [Zn3(H2O)2(tpt)­(L2)2] n (3). 1,2,4,5-Tetrasubstituted phenyl and diphenyl coligands have assisted in honeycomb-shaped, pillared-layer, and cuboid-like frameworks via synergetic binding of carboxylate, sulfonate and hydroxyl moieties: {[Zn2(tpt)­(H2L3)­(L3)0.5]·0.5H2O} n (4, H4L3 = 2,5-dihydroxyltelephthalic acid), {[Zn2.5(tpt)­(μ-OH)­(L4)]·1.5H2O} n (5, H4L4 = 5-sulfobenzene-1,2,4-tricarboxylic acid), and {[Zn3(H2O)0.5(tpt)2(μ-OH)­(L5)1.25]·5H2O} n (6, H4L5 = 3,3′-disulfonyl-4,4′-biphenyldicarboxylic acid). More significantly, the changeable donor surroundings around the Zn­(II) ions have optimized the ligand-field geometries, giving rise to variable band gaps and band potentials. Resulting from the effective isolation and migration of the charge carriers and much stronger oxidizing ability of the valence band, the cuboid-shaped framework 6 has exhibited the best photodegradation activity toward the MB pollutant, up to 89% after 4 h UV illumination. These observations have systematically revealed the consequence of the ligand field on the CP photocatalysts in organic dye photodecomposition.

Construction of a 3D Metal–Organic Framework and Its Composite for Water Remediation via Selective Adsorption and Photocatalytic Degradation of Hazardous Dye

“…MOFs as a semiconducting catalyst can absorb photons and generate electron–hole pairs in conduction and valance bands. − Upon irradiation of sunlight, the organic linkers act as an electron-releasing agent via a conjugation system to metal ions . The hopping of electrons from one place to another place triggers the redox mechanism.…”

A multifunctional [CdI4]2−·[H2Bimb]2+complex to probe high performance photocatalytic degradation of methyl violet and fluorescent detection of Cr2O72−and Hg2+ions

“…The surface of the active catalyst included the e À -h + pair, which was captured by oxygen and water molecules, along with the corresponding dye molecules. 64,65 H 2 O molecules in the VB section were attached and tricked into becoming highly reactive hydroxyl (OH ) radicals. Superoxide (O2 À ) radical anions were produced by the simultaneous interaction of dissolved molecular oxygen present in H 2 O molecules with the electrons (e À ) in the CB of the corresponding catalyst.…”

Bifunctional Self-Penetrating Co(II)-Based 3D MOF for High-Performance Environmental and Energy Storage Applications

“…The surface of the active catalyst included the e − −h + pair, which was captured by oxygen and water molecules, along with the corresponding dye molecules. 87,88 H 2 O molecules in the VB section were attached and tricked into becoming highly reactive hydroxyl (OH • ) radicals. The dissolved molecular oxygen present in H 2 O molecules simultaneously interacted with the electrons (e − ) in the CB of the corresponding catalyst to produce superoxide (O 2…”

“…The catalyst was treated under visible light, and e – was transferred from the VB to the CB via an appropriate band gap energy ( E g ), resulting in the generation of electron-deficient h + . The surface of the active catalyst included the e – –h + pair, which was captured by oxygen and water molecules, along with the corresponding dye molecules. , H 2 O molecules in the VB section were attached and tricked into becoming highly reactive hydroxyl (OH • ) radicals. The dissolved molecular oxygen present in H 2 O molecules simultaneously interacted with the electrons (e – ) in the CB of the corresponding catalyst to produce superoxide (O 2 • – ) radical anions.…”