Metal-organic Frameworks Photocatalysts Research Articles

Synergistic interaction of Re complex and amine functionalized multiple ligands in metal-organic frameworks for conversion of carbon dioxide

A metal-organic framework (MOF) is composed of secondary building units (SBUs) of metal ions and organic ligands to link each SBU. Moreover, the photosynthetic synthesis of a valuable CO chemical from carbon dioxide (CO2) represents an important class of appealing methods. Herein, we find that a molecular photocatalyst with high selectivity and activity can be designed via a fine balance in the proximity of Re complex (ReI(CO)3(BPYDC)(Cl), BPYDC = 2,2′-bipyridine-5,5′-dicarboxylate) and -NH2 functionalized multiple ligands composing a MOF photocatalyst, denoted as Re-MOF-NH2. These ligands in Re-MOF-NH2 has been confirmed by infrared, UV-visible, and 1H nuclear magnetic resonance spectra. Moreover, we show from extended X-ray absorption fine structure and in-situ infrared spectra that the bond corresponding to Re-CO upon introduction of -NH2 functional groups is divided into asymmetric bonds of 1.4 Å and 2.3 Å along with different CO2 vibrations, thus making the configuration of carbonyl groups in a Re metal complex become asymmetric in addition to aiding formation of CO2 intermediates within Re-MOF-NH2. Indeed, both of the uneven electron distribution in asymmetric carbonyl groups for Re-CO and the intermolecular stabilization of carbamate intermediates are proven to give the approximately 3-fold increase in photocatalytic activity for conversion of CO2 into CO.

Ni(dmgH)2 complex coupled with metal-organic frameworks MIL-101(Cr) for photocatalytic H2 evolution under visible light irradiation

Metal-organic frameworks (MOFs) have been tremendously used as photocatalysts for H2 generation in recent years. Lacking native active sites (so-called co-catalyst) for H2 generation motivates the incorporation of noble metals and their molecular complexes, hydrogenase active site mimics into MOFs to promote H2 generation. We herein report an noble-metal-free photocatalytic H2 generation system consisting of Erythrosin B dye-sensitized MIL-101(Cr) as a light absorber and Ni(dmgH)2 as a co-catalyst. It is found that Ni(dmgH)2 can serve as an efficient co-catalyst to boost H2 generation in the presence of triethanolamine (TEOA) as an electron donor under visible light irradiation. The optimal MIL-101(Cr)/Ni(dmgH)2 hybrid (5 wt% Ni(dmgH)2) displays a hydrogen H2 rate of 45.5 μmol h−1, which is 10 times greater than the control sample without Ni(dmgH)2 loading. This paper provides a novel design route for active H2 generation systems by combining molecular complexes of earth-abundant metal and MOFs photocatalysts.

Tailoring the Optical Absorption of Water-Stable Zr(IV)- and Hf(IV)-Based Metal-Organic Framework Photocatalysts.

New Zr(IV)- and Hf(IV)-based metal-organic framework photocatalysts, termed VNU-1 and VNU-2 (where VNU = Vietnam National University), were synthesized and their resulting structures fully characterized. By employing a highly π-conjugated linker, namely 1,4-bis(2-[4-carboxyphenyl]ethynyl)benzene, the optical absorption properties were effectively red-shifted into the visible light region. This strategy, coupled with the high water stability of the materials, led to enhanced MOF-driven photocatalytic degradation, under ultraviolet-visible light, of organic dye pollutants commonly found in wastewater.

Construction of Interpenetrated Ruthenium Metal-Organic Frameworks as Stable Photocatalysts for CO2 Reduction.

Poor stability has long been a major obstacle to the practical applications of metal-organic framework (MOF) photocatalysts. This problem can be overcome by the use of structural interpenetration. In this work, by modifying Ru metalloligands, we have rationally designed two Ru-polypyridine based MOFs (with non-interpenetrated and interpenetrated structures, respectively), both of which exhibit similar photocatalytic activities for CO2 photoreduction. Remarkably, the interpenetrated Ru-MOF possesses good photocatalytic durability and recyclability, and shows much higher thermal and photic stability in comparison with its non-interpenetrated counterpart. To the best of our knowledge, this is the first time that the stability of MOF photocatalysts was improved by using structural interpenetration.

UV‐Light‐Driven Photocatalysts of Metal‐Organic Frameworks Based on Acylamide‐Inserted Multi‐Carboxylic Acid

AbstractTwo functional metal‐organic frameworks (MOFs), [Zn·L]·[+H2N(CH3)2]2(DMF)0.5(H2O)3 (1) and [Cu2L(H2O)2]·xG (G = solvent molecule) (2) [H4L = bis(3,5‐dicarboxypheny1)terephthalamide] were synthesized under solvothermal conditions. Their photoresponses in the UV region make them promising candidates for photodegradation of Rhodamine B (RhB) under UV light irradation. We studied the photocatalytic activities of the two MOFs and polyaniline (PANI) composite materials (named PANI/MOFs), which were prepared by loading the PANI on the surface of MOFs. The results indicate that PANI/MOFs composite materials exbibit excellent photostabilities and higher photocatalytic activities than the pure MOFs photocatalysts for degradation/removal of organic pollutants from wastewaters.

Electronic effects of ligand substitution on metal-organic framework photocatalysts: the case study of UiO-66.

UiO-66-X (X = H, NH2, NO2, Br) have been successfully synthesized and tested for their photocatalytic activity in water treatment. Results show that electronic effect of the ligand substituents greatly affects the photocatalytic activity of UiO-66. The rates obtained by different substituents are linearly correlated with their Hammett coefficients.

Structures, photoluminescence and photocatalytic properties of two novel metal–organic frameworks based on tetrazole derivatives

Two novel, efficient metal organic framework photocatalysts based on silver salts and tetrazolate derivatives have been successfully prepared and characterized.

Development of a novel one-pot reaction system utilizing a bifunctional Zr-based metal–organic framework

A novel one-pot reaction system is developed by utilizing a bifunctional metal–organic framework photocatalyst (Zr-MOF-NH2). Zr-MOF-NH2 promotes sequential photocatalytic oxidation and Knoevenagel condensation reaction to produce benzylidenemalononitrile from benzyl alcohol and malononitrile under UV-light irradiation.

Efficient hydrogen production and photocatalytic reduction of nitrobenzene over a visible-light-responsive metal–organic framework photocatalyst

Efficient hydrogen production and photocatalytic reduction of nitrobenzene were achieved by using a Pt-deposited amino-functionalised Ti(IV) metal–organic framework (Pt/Ti-MOF-NH2) under visible-light irradiation. XRD and N2 adsorption measurements revealed that crystalline microporous structures were formed and maintained even after the Pt deposition. The photocatalytic activity for the visible-light-promoted hydrogen production was improved through the optimization of the deposition amount of Pt as a cocatalyst. The optimised amount of Pt was determined to be 1.5 wt%. The results of in situ ESR measurements clearly indicate that the reaction proceeds through the electron transfer from the organic linker to deposited Pt as a cocatalyst by way of titanium-oxo clusters. In addition, the Pt/Ti-MOF-NH2 photocatalyst was found to catalyse photocatalytic reduction of nitrobenzene under visible-light irradiation. It was also confirmed that the catalyst can be reused at least three times without significant loss of its catalytic activity.

Hydrogen Production Promoted by Visble Light-Responsive MOF (Metal-Organic Framework) Photocatalyst

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An Amine‐Functionalized Titanium Metal–Organic Framework Photocatalyst with Visible‐Light‐Induced Activity for CO2 Reduction

Let your light shine: the photocatalytic reduction of carbon dioxide to the formate anion under visible light irradiation is for the first time realized over a photoactive Ti-containing metal-organic framework, NH(2)-MIL-125(Ti), which is fabricated by a facile substitution of ligands in the UV-responsive MIL-125(Ti) material.

An Amine‐Functionalized Titanium Metal–Organic Framework Photocatalyst with Visible‐Light‐Induced Activity for CO2 Reduction

Aus UV wird sichtbar: Die photokatalytische Reduktion von CO2 zu Formiat wurde erstmals mit sichtbarem Licht erreicht. Als Photokatalysator diente eine photoaktive titanhaltige Metall-organische Gerüstverbindung, die durch eine einfache Ligandensubstitution in dem auf UV-Licht reagierenden MIL-125(Ti)-Material erhalten wurde (siehe Schema; TEOA=Triethanolamin).