No abstract

CO2 photoreduction is a promising avenue to alleviate climate change and energy shortage, and highly active and selective photocatalysts have been pursued. Discrete metal–organic cages (MOCs) with tunable structures and dispersion not only render integration of multiple functional moieties but also facilitate the accessibility of catalytic sites, yet the studies of MOCs on CO2 reduction are still underexplored. Herein, a single molecular cage of the Ir­(III) complex-decorated Zr-MOC (IrIII-MOC-NH2) is proposed for CO2 photoreduction. IrIII-MOC-NH2 shows high reactivity and selectivity in converting CO2 into CO under visible light. The selectivity is of 99.5% and the turnover frequency reaches ∼120 h–1 which is 3.4-fold higher than that of bulk IrIII-MOC-NH2 and two orders of magnitude higher than that of the classical metal–organic framework counterpart (IrIII-Uio-67-NH2). The apparent quantum yield is up to 6.71% that ranks the highest among the values reported for crystalline porous materials. Moreover, aggregation-induced deactivation of the Ir­(III) complex is restrained after incorporating into MOC-NH2. The density functional theory calculations and dedicated experiments including cyclic voltammetry, mass spectrometry and in situ IR show that the Ir­(III) complex is the catalytic center, and −NH2 in the framework plays the synergetic role in the stabilization of the transition state and CO2 adducts.

In this work, a Cr-based MOF (MIL-101(Cr))/reduced grapheme oxide(rGO) electrocatalyst was prepared through a one-pot hydrothermal method. The obtained composite was characterized via scanning electron microscopy, transmission electron microscopy, X-ray diffraction and other standard techniques. Electrochemical methods were adopted to study the electrocatalytic ability of the composite. The results imply that, compared to the single components, it exhibits higher electrocatalytic activity for the reduction of metronidazole and stripping of Cd 2 + and Pb 2 + . Optimizing the ratio of MIL-101(Cr) and rGO, an electrochemical sensor was prepared using MIL-101 (Cr)/rGO-20 and used for detection of metronidazole, Cd 2 + and Pb 2 + , respectively. The linear range for metronidazole can be divided in two parts, i. e. from 0.5 to 200 mM and from 200 to 900 mM. The limit of detection is 0.24 mM (S/N = 3, n = 10). Likewise, it also exhibits a wide linear range from 0.05 to 6.0 mM for the detection of Cd 2 + and Pb 2 + . The corresponding detection limits are found to be 5.2 nM and 3.0 nM (S/N = 3, n = 10), respectively. The proposed sensor also possesses superb selectivity, reproducibility, stability and can be applied to detect real samples with desired recovery rates. In addition, the possible reduction mechanism of metronidazole and adsorption mechanism of Cd 2 + and Pb 2 + were further discussed simply in this work.[a] J.

Light irradiation could affect electronic properties of catalysts and the introduction of appropriate light into the electrocatalysts may have a significant impact on the electrocatalytic process, but it has not...

Photocatalytic carbon dioxide reduction (CO2RR) is considered to be a promising sustainable and clean approach to solve environmental issues. Polyoxometalates (POMs), with advantages in fast, reversible, and stepwise multiple-electron transfer without changing their structures, have been promising catalysts in various redox reactions. However, their performance is often restricted by poor thermal or chemical stability. In this work, two transition-metal-modified vanadoborate clusters, [Co­(en)2]6­[V12B18O54­(OH)6]·17H2O (V12B18–Co) and [Ni­(en)2]6­[V12B18O54­(OH)6]·17H2O (V12B18–Ni), are reported for photocatalytic CO2 reduction. V12B18–Co and V12B18–Ni can preserve their structures to 200 and 250 °C, respectively, and remain stable in polar organic solvents and a wide range of pH solutions. Under visible-light irradiation, CO2 can be converted into syngas and HCOO– with V12B18–Co or V12B18–Ni as catalysts. The total amount of gaseous products and liquid products for V12B18–Co is up to 9.5 and 0.168 mmol g–1 h–1. Comparing with V12B18–Co, the yield of CO for V12B18–Ni declines by 1.8-fold, while that of HCOO– increases by 35%. The AQY of V12B18–Co and V12B18–Ni is 1.1% and 0.93%, respectively. These values are higher than most of the reported POM materials under similar conditions. The density functional theory (DFT) calculations illuminate the active site of CO2RR and the reduction mechanism. This work provides new insights into the design of stable, high-performance, and low-cost photocatalysts for CO2 reduction.