Photocatalytic hydrogen evolution activity over Pt-assisted metal-organic frameworks dominated by transition metal ions and local coordination environments

Abstract

Three isostructural pillared-layer frameworks with M-BDC-X layers supported by ditopic HL connectors, [M(HL)(BDC)0.5X] n (HL = 4′-(4-hydroxyphenyl)-4,2′:6′,4″-terpyridine, BDC = terephthalate, M = Cd, X = Cl for (1), M = Cd, X = formate for (2), and M = Co, X = formate for (3)), were solvothermally synthesized, and used as photocatalysts for Pt-assisted visible-light-initiated hydrogen evolution from water splitting. These water-durable frameworks exhibit varied hydrogen production rates of 361.2, 271.3, and 327.5 μmol · g−1 · h−1 in 12 h due to their slightly different donor environments of the octahedral CdII and CoII ions. Further experimental and theoretical investigations reveal that the metal ions and the local coordination surroundings have essentially dominated the conduction band minimum and electric resistance of the charge transport, which play highly important roles for the improved catalytic hydrogen evolution ability. These findings demonstrate the electronic effect of the slightly ligand field modifications on the boosting hydrogen generation activity in the noble metal-assisted MOF photocatalytic systems.

Structural Adjustments of Zn(II)‐Terpyridine Analogues by Pendent of Coligand: Solvothermal Syntheses, Crystal Structure, and Photophysical Behavior

“…[19] The ZnÀ O and ZnÀ N distances vary between 1.9485(18) and 2.203(2) Å (Table 2), highly comparable to Zn(II)-complexes with carboxylate and/or five-and six-membered N-heterocyclic ligands (such as triazolyl, pyridyl, and pyrazinyl derivative). [20,21] Acting as a ditopic connector, the unique L 1 À anion presents neutral dipyrazinylpyridyl and deprotonated tetrazolate moieties to contact with metal ions in a chelating-bridging mode. Apparently, the functional tetrazolyl moiety has enriched the coordination behavior of the terpyridine-family ligand, as compared with anilino and phenol functionalized terpyridine.…”

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

“…21,22 Nevertheless, the ligand-field effect of the CP photocatalyst on the energy band structure and even the photocatalytic activity have been inadequately investigated thus far. 23,24 Organic dye molecules discharged from the textile, rubber, and paper industries have emerged as one of the main pollutants in industrial wastewater. Since most dyestuffs are hazardous, stable, and hardly degradable by conventional biological treatments, high levels of these contaminants in water body inevitably bring severe destruction to aquatic organisms and human bodies because of their mutagenic and carcinogenic effects.…”

“…By skillful incorporation of photoactive organic ligands and elaborate optimization of the ligand fields around the active metal center, the well-designed CPs could integrate a semiconductive nature for efficient photogenerated charge carriers under irradiation of different light sources. − These semiconductive CPs with abundant and highly reactive charge carriers have consequently exhibited promising photochemical activity toward dye pollutant degradation, CO 2 photoreduction, and photocatalytic hydrogen and oxygen evolution. − In comparison with typical inorganic semiconductors, these extended CPs have various inherent merits of easy modifications, zero secondary pollution, improved solar energy utilization, and long-term durability, ensuring their broad use as photocatalysts for high-quality reclaimed water in environmental remediation. Various strategies have thus been implemented to strengthen the photocatalytic performance of the CP photocatalysts to date, including broadening the chromophoric backbone of the organic ligand to enrich the light absorption, anchoring coordinatively unsaturated metals or metal clusters as active sites, − fabricating substrate-preferred voids to facilitate the mass transport, and so on. , Nevertheless, the ligand-field effect of the CP photocatalyst on the energy band structure and even the photocatalytic activity have been inadequately investigated thus far. , …”

“…A highly efficient, long-term stable, and easily synthesized photocatalyst is vital for enhancement in the dye photodegradation. As one of the popular three-connected linkages, 2,4,6-tris­(4-pyridyl)-1,3,5-triazine (tpt) possesses a rigid conjugated backbone and three exterior coordinative pyridyl spacers, having strong UV-light-responsive ability and orientation-related binding selectivity. − Especially, on incorporation with an O-containing auxiliary ligand and configurationally flexible Zn­(II) ion, a large number of semiconductive CP photocatalysts have been hopefully well-designed with different local coordination polyhedra and extended frameworks, , representing good opportunities for interpreting the ligand-field function on the band structures and photocatalytic capacity. Herein, coordination-driven self-assembly of a Zn­(II)-tpt-based ternary system has been systematically investigated by varying O-containing coligands, and the resulting Zn­(II)-CPs were used as photocatalysts to trigger methylene blue (MB) degradation to evaluate the ligand-field effect on the energy band optimization and photocatalytic activity.…”

Synergistic adsorption and photocatalytic degradation of persist synthetic dyes by capsule-like porphyrin-based MOFs

“…To further promote the photocatalytic efficiency of MOFs, the organic photosensitizers were employed as the linker and thus resulting MOFs depicted the self-sensitivity to the visible-light irradiation [10,11]. Among them, porphyrins are considered to be one of the excellent photosensitizers relying on their visible-light harvesting ability owing to the S and Q-bands absorption edge [12].…”