Coordinatively Unsaturated Sites Research Articles

A Ru-porphyrin metal-organic framework with Mn2+ paddlewheel nodes for the selective oxidation of C(sp3)-H bonds.

The activation and selective functionalization of inert C(sp3)-H bonds is fundamental for industrial applications and occupies a very important place in industry, but it remains a great challenge in current synthetic chemistry. In this paper, we report an approach for activating reactive tert-butyl peroxyl radicals by modifying Ru-porphyrin into metal-organic frameworks (MOFs) for the activation of inert C(sp3)-H bonds. Under mild conditions, the Ru-porphyrinyl MOF can activate the peroxyl radical, extracting a hydrogen atom from the inert C(sp3)-H bond. Mn2+ paddlewheels with unsaturated coordination sites were introduced into the MOF, and direct oxidative conversion using environmentally friendly oxygen provides a new pathway to activate the inert C(sp3)-H bond.

Controllable creating mesoporous coordination unsaturated sites in UiO-66 single crystals for efficient conversion of hydrogen sulfide into polysulphur

We report herein a facile pyrolysis etching strategy for the fabrication of UiO-66-xs single crystals with tunable coordination unsaturated zirconium sites (Zr-CUS) as well as interconnected mesoporosity. The synthesis is realized by having pristine UiO-66-xs subjected to thermal treatment, which results in the selective decomposition of thermal-sensitive organic linkers and hence the creation of permanent mesoporosity, leaving abundant Zr-CUS with enhanced degree of exposure. The prepared hierarchically porous UiO-66-xs (HP-UiO-66-xs) were innovatively applied for mild oxidation of H2S into polysulphur, achieving near 100 % H2S conversion and polysulphur selectivity in a wide range of temperatures. The superior activities can be well maintained in a continuous test of over 50 h. The Zr-CUS of HP-UiO-66-xs effectively activate H2S and O2 via the “adsorption dissociation tandem hydrogen transfer” mechanism, and the abundant mesochannels ensure efficient transport of reactants and bulky products in and out HP-UiO-66-xs, leading to catalytic activities superior to those of traditional H2S selective oxidation catalysts.

Use of molecular simulation for evaluating adsorption equilibrium of inhalation anaesthetic agents on metal–organic frameworks

AbstractMetal–organic frameworks (MOFs) were studied as alternatives to zeolites and activated carbon for adsorptive removal of wasted inhalation anaesthetic agents (IAA). Monte Carlo simulation was used to predict equilibrium adsorption isotherms of IAA on selected MOFs. Rather than generic forcefields (FFs), the all‐atom FF parameters published by Arcario were used for IAA modelling. Continuous fractional component Monte Carlo (CFCMC) proved crucial for speedy simulation of large molecules. We found that allocating 70% probability to the CFlambdaSwap move gave optimum fits between simulation and experiment. The simulations provided us with an insight into the adsorption mechanisms of IAA in these structures. Heats of adsorption, Brauner‐Emmet‐Teller (BET) surface area, and total pore volume were deduced to be the crucial parameters for low, medium, and high range of relative pressures in the isotherm. Therefore, the chromium atoms in MIL‐101‐Cr are better adsorbers of IAA than MIL‐100‐Al at lower pressures despite the similarities in terms of the type of linkers and topology. Our simulation results corroborated the earlier published studies on the self‐association behaviour of sevoflurane molecules based on the experimental isotherms reported for MOF‐177‐Zn. Finally, the high polarity of IAA is thought to explain good low‐pressure simulation/experiment data agreement for the MOFs possessing coordinatively unsaturated sites (CUS) despite using generic DREIDING FF for the framework atoms. Our in‐house parsing code helped realize that the grand‐canonical Monte‐Carlo simulation speed is not the same for all pressure points but decreases for higher pressure points. This can be explained by increased density of the adsorbates making successful trial moves less probable.

High-performance carbon@ metal oxide nanocomposites derived metal–organic framework-perovskite hybrid boosted microwave-induced catalytic degradation of norfloxacin: Performance, degradation pathway and mechanism

Herein, FeCo@C-LFCx (FeCo@C-xLaFeCoO3) materials were prepared by high-temperature carbonation based on the construction of Fe/Co metal–organic framework columns with LaCoO3 (FeCo-MOF-LFCx) by in-situ extraction and synchronous coordination growth strategy. This strategy could improve the defects of perovskite materials such as easy aggregation, poor stability and poor specific surface area. The results demonstrated that the degradation rate of FeCo@C-LFC1.0 for norfloxacin (NOR, 20 mg/L) was 93.81% within 15 min. Co-BTC column nanocolumns and spongy Fe-BTC were successfully formed. Compared with LaFeCoO3, the specific surface area (89.9 m2/g) and pore volume (0.101 cm3/g) of FeCo@C-LFC1.0 after carbonization were increased by 16.3 times and 9.2 times, respectively. FeCo@C-LFCx could produce more structural defects and coordination unsaturated sites, promote microwave absorption. Vo and C = O on the material surface were involved in the activation of PMS. Moreover, quenching experiments and EPR verified that 1O2, OH, and SO4− were the main reactive radicals in the degradation process. The FeCo@C-LFC1.0 showed excellent reusability and stability. After five experiments, the removal rate of NOR remained at 91.15%. The toxicity of intermediate products was reduced. This work provided new avenues for using FeCo@C-LFC1.0 for environmental remediation.

Highly Efficient and Reusable Denitrogenation Adsorbent Obtained by the Fluorination of PMA-MIL-101.

A simple but efficient strategy to improve the ability of adsorptive denitrogenation (ADN) of MIL-101(M101) was studied by the in situ encapsulation of phosphomolybdic acid (PMA) and the subsequent purification of the as-synthesized product by the NH4F solution. After the NH4F treatment, the vast majority of PMA was removed, loss of organic ligand (BDC) was observed, and the fluorination of the hydroxyl group in the M101 structure occurred. The ADN activities of the Cr-MOF matrix composites before and after fluorination were studied in detail. The rest of PMA interacts strongly with M101 and assists the ADN activity. Coordination unsaturated metal sites (CUS) in M101 are formed after fluorination and also contribute to ADN activity. Further, fluoride anions replace most of the hydroxide groups in M101, which can promote the ADN of quinoline (QUI) and indole (IND) through an acid-base interaction and N-atom coordination with the CUS in M101. P-M101-F 5% exhibits the highest adsorptive capacity and excellent regeneration ability. Special emphasis in this work is placed on structure modulation (including PMA doping, CUS creation, and fluorination) of M101 for enhancing ADN activity, which provides a useful scaffold for future research in the rational design of MOF-based ADN catalysts.

In Situ Observation of Solvent Exchange Kinetics in a MOF with Coordinatively Unsaturated Sites.

Solvent exchange of synthesis solvent within metal-organic frameworks (MOFs) is an essential process for the activation of coordinatively unsaturated sites (CUS) to achieve an optimal surface area; activation of the CUS is required to exploit the versatile applications of MOFs. However, it is challenging to replace CUS-bound synthesis solvent prior to MOF activation, which can lead to a structural collapse and reduced surface area post-evacuation. Herein, we quantify the exchange behavior of a copper paddlewheel-based CUS-MOF (HKUST-1) in the presence of three different solvents: ethanol (EtOH), dichloromethane (DCM), and N,N-dimethylformamide (DMF). The DMF release profiles are monitored via in situ observation of the exchange solvent composition via 1H NMR and Raman spectroscopy at the macroscopic scale. Furthermore, the change in solvent within a single crystal is measured to directly elucidate the exchange behavior. We demonstrate the DMF release profile from HKUST-1 exhibits different rate laws depending on whether the solvent exchange occurs at the CUS or is purely diffusive through the pores. This contribution represents the first characterization of release from a CUS-MOF as a function exchange solvent and reveals that solvent exchange in a CUS-MOF is not diffusion-limited, but rather is limited by the solvent exchange kinetics at the metal center. Insights from this study can be generalized to the variety of copper-paddlewheel-based MOFs, informing best practices for solvent exchange.

Tuning active sites in MoS2-based catalysts via H2O2 etching to enhance hydrodesulfurization performance

A H2O2 etching strategy was adopted to introduce coordinatively unsaturated sites (CUS) on MoS2-based catalysts for dibenzothiophene (DBT) hydrodesulfurization (HDS). The CUS concentrations on MoS2 slabs were finely regulated by changing the concentrations of H2O2 solution. With the increasing H2O2 concentrations (0.1–0.3 mol/L), The CUS concentrations on MoS2 slabs increased gradually. However, the high-concentration H2O2 etching (0.5 mol/L) increased the MoOxSy and MoO3 contents on MoS2 slabs compared to etching with the H2O2 concentration of 0.3 mol/L, which led to the less CUS concentration in the sulfided Mo–H-0.5 catalyst than in the sulfided Mo–H-0.3 catalyst. A microstructure-activity correlation indicated that the CUS introduced by H2O2 etching on MoS2 slabs significantly enhanced DBT HDS. Different Co loadings were further introduced into Mo–H-0.3, which had the most CUS concentration, and the corresponding 0.2-CoMo catalyst with the highest CoMoS content (3.853 wt%) exhibited the highest reaction rate constant of 6.95 × 10−6 mol g−1 s−1 among these CoMo catalysts.

Oxygen vacancy self-doped single crystal-like TiO 2 nanotube arrays for efficient light-driven methane non-oxidative coupling

Photocatalytic non-oxidative coupling of methane (PNOCM) is a mild and cost-effective method for the production of multicarbon compounds. However, the separation of photogenerated charges and activation of methane are the main challenges for this reaction. Here, single crystal-like TiO₂ nanotubes (V_O-p-TNT) with oxygen vacancies (V_O) and preferential orientation were prepared and applied to PNOCM. The results demonstrate that the significantly enhanced photocatalytic performance is mainly related to the strong synergistic effect between preferential orientation and V_O. The preferential orientation of V_O-p-TNT along [001] direction reduces the formation of complex centers at grain boundaries as the form of interfacial states and potential barriers, which improves the separation and transport of photogenerated carriers. Meanwhile, V_O provides abundant coordination unsaturated sites for methane chemisorption and also acts as electron traps to hinder the recombination of electrons and holes, establishing an effective electron transfer channel between adsorbed CH₄ molecule and photocatalyst, thus weakening C–H bond. In addition, the introduction of V_O broadens the light absorption range. As a result, V_O-p-TNT exhibits excellent PNOCM performance and provides new insights into catalyst design for CH₄ conversion.

High Ionic Conductivity Motivated by Multiple Ion‐Transport Channels in 2D MOF‐Based Lithium Solid State Battery

AbstractMetal‐organic frameworks (MOFs) have been proposed as novel fillers for constructing polymer solid electrolytes based composite electrolytes. However, MOFs are generally used as passive fillers, in‐depth revealing the binding mode between MOFs and polyethylene oxide (PEO), the critical role of MOFs in facilitating Li+ transport in solid electrolytes is full of challenges. Herein, inspired by density functional theory (DFT) the 2D‐MOF with rich unsaturated metal coordination sites that can bind the O atom in PEO through the metal–oxygen bond, anchor TFSI− to release Li+, resulting in a remarkable Li+ transference number of 0.58, is reported according well with the experimental results and molecular dynamics (MD) simulation. Impressively, after the introduction of the 2D‐MOF, the Li+ can rapidly hop along the benzene ring center within the 2D‐MOF plane, and the interface between the benzene ring and PEO can also serve as a fast Li+ migration pathway, delivering multiple ion‐transport channels, which present a high ion conductivity of 4.6 × 10−5 S cm−1 (25 °C). The lithium symmetric battery is stable for 1300 h at 60 °C, 0.1 mA cm−2. The assembled lithium metal solid state battery maintains high capacity of 162.8 mAh g−1 after 500 cycles at 60 °C and 0.5 C. This multiple ion‐transport channels approach brings new ideas for designing advanced solid electrolytes.

Differences between atomically-dispersed and particulate Pt supported catalysts on synergistic photothermocatalytic oxidation of VOCs from cooking oil fumes

The control of volatile organic compounds (VOCs) from cooking oil fumes via synergic photothermocatalytic oxidation not only saves energy, but also helps to reduce carbon emissions. Differences between the copper oxide−ceria (CC) supported atomically-dispersed (Pt1/CC) and particulate Pt (PtNPs/CC) on photothermocatalytic heptane oxidation were investigated. The conversion efficiency at 170 oC of heptane oxidation over the Pt1/CC catalyst was 55% higher than that over the PtNPs/CC catalyst. PtNPs/CC showed a larger capacity of heptane adsorption, but limited amounts of the adsorbed oxygen and active surface lattice oxygen species were difficult to completely oxidize the over-adsorbed heptane. Heptane and its intermediates gradually accumulated at the active sites, resulting in poor catalytic activity and stability. However, Pt1/CC possessed a strong electron donating ability due to its unique coordination unsaturated sites and electron structure, which was conducive to oxygen activation. This allowed rapid conversion of heptane and intermediates, accelerating oxidation of the adsorbed heptane to CO2 and H2O. The complete oxidation of 500 ppm heptane was basically achieved at 190 oC and an optical power density of 300 mW/cm2.

An ultra-high electrochemical performance of surface-rich boron induced multi-metal centered heterocatalyst for overall water splitting

Preparing highly active and stable bifunctional electrocatalyst for hydrogen evolution and oxygen evolution reactions (HER/OER) in alkaline conditions is essential to reducing energy losses in the water-alkali industry but challenging undertaking. A simple room-temperature boronization approach is projected to fabricate boronated CuCo2O4/NiO nanoarrays for bifunctional catalytic activities. Herein, a modest hydrothermal process is applied to cultivate heterostructure CuCo2O4/NiO nanoarrays by spanning ternary metal (Cu–Co–Ni) oxides followed by a boronization strategy on a self-supporting nickel foam substrate. The outcome of the experiment revealed that ultra-surface optimization with boron permits accelerated electron transfer and multiplies the access of surface coordinative unsaturated active sites. As a result, B–CuCo2O4/NiO nanoarrays supported on nickel foam (NF) require fewer overpotentials of 52 mV for the hydrogen evolution reaction and 294 mV for the oxygen evolution reaction to achieve a current density of 20 mA cm−2. Surprisingly, employing B–CuCo2O4/NiO@NF as a bifunctional electrocatalyst for overall water splitting empowers an alkaline electrolyzer with a current density of 10 mA cm−2 and a cell voltage of 1.54 V. The current study could pave the groundwork for the rise of boron-induced Cu–Co–Ni oxides hetero-assemblies for electrocatalysis.

Single‐Atom Fe Catalyst for Catalytic Ethane Dehydrogenation to Ethylene

AbstractThe single atom catalysts (SACs) show unique catalytic performance in heterogeneous reactions owing to unsaturated coordination sites and high metal atom dispersion. Herein, a simple wet impregnation method was utilized to synthetize of Fe−Al2O3 catalysts. The Fourier transformation infrared spectroscopy (FTIR) revealed that abundant OH group attached to the support (Al2O3) surface facilitating formation of isolated Fe single atom. High resolution transmission electron microscope (HR‐TEM) and extended X‐ray absorption fine structure (EXAFS) confirmed the Fe single atom architecture. Fe−Al2O3 (4.5 wt %) performed enhanced stability and activity on ethane dehydrogenation reaction.

Pt-functionalized Amorphous RuOx as Excellent Stability and High-activity Catalysts for Low Temperature MEMS Sensors.

The unsaturated coordination and abundant active sites endow amorphous metals with tremendous potential in improving metal oxide semiconductors' gas-sensing properties. However, the amorphous materials maintain the metastable status and easily transfer into the lower-active crystals during the gas-sensing process at high working temperatures, significantly limiting their further applications. Here, a bimetal amorphous PtRu catalyst is developed by accurately regulating the introduction of Pt species into amorphous RuOx supports to realize the highly active and stable H2 S gas-sensing detection. It is found that incorporation of low-concentration Pt species can effectively maintain the amorphous state of initial RuOx and delay the crystallization temperature as high as 100°C. Further, ex situ XPS and in situ Raman spectroscopy analysis confirm that active Pt species can facilitate H2 S adsorption by strong Pt-S coordination and dissociate the sulfur species to the surrounding support, which contribute to the chemisorption and sensitization of H2 S. Meanwhile, electron transport at the interface between Pt, RuOx and ZnO further activates the reaction process at the surface of the gas-sensitive material. The final PtRu-modified ZnO (PtRu/ZnO) sensor enables the detection of H2 S in the ultra-low concentration range of 15-2000 ppb with remarkable stability.

Ein neuartiger T-förmiger 14-Elektronen-Iridium(I)-Komplex stabilisiert durch eine agostische Ir–H-Wechselwirkung

AbstractThe reaction of [{Ir(µ-Cl)(coe)2}2] (1, coe =cis-cyclooctene) with the bulky tertiary phosphane P(o-tolyl)3in dichloromethane at room temperature was investigated. It afforded in good yield the tri-coordinate iridium(I) complex [IrCl{P(o-tolyl)3}2] (2) which was characterized in the solid state by a single-crystal X-ray diffraction study revealing a molecular structure of a rare tri-coordinate complex. The iridium(I) complex is stabilized by an agostic interaction of a hydrogen atom from the methyl group of the bulky phosphane ligand to fill the fourth unsaturated coordination site. The title compound crystallized from dichloromethane/diethyl ether as orange crystals in a mixture of two modifications (monoclinicP21/c,2a, and orthorhombicPbca,2b). The co-existence of the two components as a nearly 1:1 mixture in the crystalline bulk material was supported by solid-state31P{1H} NMR measurements.

Stereospecific Single-Pot Route to Chiral Imidazolidines from Aziridines Using a 2D Cu Metal–Organic Framework

The role of coordinatively unsaturated sites (CUS) in metal-organic framework (MOF)-catalyzed organic transformation is vital; however, the design and generation of such sites are challenging. We, therefore, report the synthesis of a novel two-dimensional (2D) MOF, [Cu(BTC)(Mim)]n (Cu-SKU-3), with pre-existing unsaturated Lewis acid sites. The presence of these active CUS facilitates a ready-to-use attribute in Cu-SKU-3, thereby subsiding the lengthy activation processes associated with MOF-based catalysis. The material has been completely characterized using single crystal X-ray diffraction (SCXRD), powder XRD (PXRD), thermogravimetric analysis (TGA), carbon, hydrogen, and nitrogen (CHN), Fourier-transform infrared (FTIR), and Brunauer-Emmett-Teller (BET) surface area analyses. We directly utilize Cu-SKU-3 for the synthesis of biologically valued chiral imidazolidine motifs in a one-pot fashion starting from aziridines. The chiral imidazolidines are synthesized in good yield (up to 89%) and with high optical purity (ee > 98-99%). Mechanistically, the transformation proceeds in a tandem fashion through stereospecific ring-opening of aziridines followed by the intramolecular cyclization (via sp3 C-H functionalization) reaction forming chiral imidazolidines. The material has an excellent heterogeneous attribute and can be reused several times for one-pot catalytic cycles.

Facile integration of hydroxyl ionic liquid into Cr-MIL-101 as multifunctional heterogeneous catalyst for promoting the efficiency of CO2 conversion

Rational integration of functional ionic liquids (ILs) into metal-organic frameworks (MOFs) is an intriguing and challenging strategy for design of fully heterogeneous catalytic systems for the synthesis of cyclic carbonates from cycloaddition of CO2 and epoxides. This study demonstrates a facile and versatile post-synthetic modification approach for incorporating hydroxyl-functionalized imidazolium IL into Cr-MIL-101 (HImBr@Cr-MIL-101) via coordinative bonding interaction between Cr CUS (coordinative unsaturated metal sites) in MOF and electron-rich –SH group in IL. The resultant HImBr@Cr-MIL-101 possesses high surface area, profitable porosity and good CO2 adsorption capacity, rendering it as an efficient heterogeneous catalyst for the cycloaddition reaction under co-catalyst and solvent free conditions. Compared to either pure Cr-MIL-101 or hydroxyl IL, HImBr@Cr-MIL-101 shows largely enhanced catalytic activity, attributing to the synergistic effect of the integrated multiple active sites, involving Cr CUS as Lewis acid, hydroxyl group as hydrogen bond donor, and bromide anion as nucleophilic reagent for ring-opening of epoxide, as well as tertiary N atom as Lewis basic site for activating CO2. This is also evidenced by the activation energy Ea catalyzed by the Cr-MIL-101-based catalysts with different functions. Notably, HImBr@Cr-MIL-101 also significantly outperforms other benchmark MOF-based catalysts. Moreover, benefited from the superb coordinative bonding interaction of the built Cr (III)–S bond, this catalyst exhibits good chemical stability and recyclability, which can be reused for at least seven runs without obvious catalytic activity depletion. This work provides a promising strategy for constructing multifunctional heterogeneous catalyst for CO2 cycloaddition reaction by highlighting the synergistic effect enabled by one host.

MRI Contrasting Agent Based on Mn-MOF-74 Nanoparticles with Coordinatively Unsaturated Sites.

The development of magnetic resonance imaging (MRI) contrasting agents (CAs) that are safer and have a higher relaxivity than Gd(III)-based agents is a significant research topic. Herein, we propose the use of a Mn-based metal organic framework (MOF), Mn-MOF-74, characterized by a safe paramagnetic center, a coordinatively unsaturated site (CUS) for aquation, and a long rotational correlation time, endowing high relaxivity. Furthermore, biocompatibility and delivery to the tumor are generally expected for MOFs that are obtainable in the nanometer size range. Drop-wise mixing of 2,5-dihydroxyterephthalic acid (DHTP) and Mn(II) acetate yielded Mn-MOF-74 with a diameter of < 150nm, which was then modified with 1-fivefold higher amounts of poly(ethylene glycol) (M.W. = 5000) to afford MOFs stably dispersed in water for at least 24h. The longitudinal and transverse relaxivity of the PEG-modified MOF was in the range of r1 = 8.08-13.5 and r2 = 32.7-46.8mM-1s-1, respectively (1.0T, 23.7-23.9°C), being larger than those of typical Gd(III)- and Mn(II)-based CAs of single-nuclear metal complexes. The in vivo imaging of a tumor-bearing mouse clearly showed that the tumor could be readily recognized due to signal enhancement (117%) in T1-weighted images, whereas other tissues showed small signal changes. These results suggest that PEG-Mn-MOF-74 can be passively delivered to tumors and can act as a high-relaxivity T1 agent.

Voltage Mediated Enhances Lithium‐Ion Storage in LiTiOPO4‐y with Oxygen Vacancy

AbstractThe oxygen vacancy modulated LiTiOPO4‐y was synthesized by simple hydrothermal and high‐temperature solid‐phase methods. X‐ray diffraction (XRD) test data analyses reveal that the density of oxygen defects in LiTiOPO4‐y can be affected by the hydrothermal reaction time. The electron paramagnetic resonance (EPR) showed signal peaks at g=2.003, which proved that oxygen defects were generated. X‐ray photoelectron spectroscopy (XPS) further demonstrated that oxygen defects exist in LiTiOPO4‐y, which led to the partial conversion of Ti4+ to Ti3+. The capacity of LiTiOPO4 was limited (less than 161 mAh g−1) by cycling potential range (0.5–3.0 V). The oxygen‐deficient LiTiOPO4‐y was used to enhance lithium‐ion storage performance by mediating voltage from 0.01 to 3.0 V. The initial capacity of oxygen‐deficient LiTiOPO4‐y, which was synthesized after hydrothermal treatment for 18 h, with an exposed (121) face, reached 563.5 mAh g−1 at the current density of 500 mA g−1. After 1500 cycles, the specific discharge capacity kept at 397.2 mAh g−1. In the oxygen‐defective LiTiOPO4‐y, multiple coordination unsaturated sites are exposed, which can not only significantly enhance ion diffusion and charge transfer, but also promote Li+ to more storage sites.

Photoelectric properties of the layered raspberry sandwich amorphous ZnCo2S4@MnCo2S4/CP composite counter electrode in semiconductor-sensitized solar cells.

Multistage amorphous materials have promising applications in the catalytic performance of dye-sensitized solar cells (DSSCs). Herein, an amorphous sheet-raspberry sandwich-like ZnCo2S4@MnCo2S4/CP composite material was rationally designed and developed as a counter electrode (CE) for DSSCs by applying a three-step hydrothermal method. The first development of the amorphous composites as CEs resulted in lower charge transfer resistance at the CE/electrolyte interface and improved the fill factor and short-circuit current density. The excellent catalytic performance is mainly attributed to the large number of unsaturated coordination sites generated by the undirected structure of the lamellar-raspberry intercalated amorphous material, the smooth ion transport interface with a self-built corrosion-resistant layer, coupled with the dual catalytic performance of the Zn, Co, and Mn composites, and the good electrical conductivity of the C substrate. When ZnCo2S4@MnCo2S4/CP was used as the CE on a Ti substrate, the photoelectric conversion efficiency was as high as 11.68% (Voc = 0.821, Jsc = 20.14 mA cm-2, and FF = 0.71) under 100 mW cm-2 light illumination. This paper provides a design idea for amorphous materials in terms of catalytic performance and a method for developing alternatives to Pt electrodes.

Novel effects of copper precursors on the adsorption and desorption of elemental mercury over copper-based sulfides: Performance, mechanism, and kinetics

BackgroundMore Hg0 adsorption onto the spent CuSx/TiO2N [Cu(NO3)2 as the Cu precursor] in the presence of O2 and SO2 and less Hg0 desorption from it occurred simultaneously after the regeneration, which was likely related to the formation of new Cu precursor (CuSO4 from the sulfation of CuO) before the sulfuration. Methods: The effects of two different Cu precursors [i.e., Cu(NO3)2 and CuSO4] on the performance of CuSx/TiO2 for Hg° capture were investigated by comparing the kinetic parameters of Hg0 adsorption and desorption. Significant findings: CuSO4 generally retained its intact structure after the calcination due to its strong heat stability, but Cu(NO3)2 was decomposed into CuO and Cu2O; therefore, both more active S22− that oxidized the physically adsorbed Hg0 to HgS and less S0 that provided the unstable adsorption sites were formed on CuSx/TiO2-S (CuSO4 as the precursor) during the sulfuration than CuSx/TiO2N. Meanwhile, the amount of unsaturated coordination sites onto CuSx/TiO2-S for Hg0 physical adsorption was significantly larger than that onto CuSx/TiO2N. Therefore, not only did Hg0 adsorb more onto CuSx/TiO2-S, but it also desorbed less from CuSx/TiO2-S. In consequence, Cu-based sulfides derived from the CuSO4 precursor were more suitable for Hg° capture from smelting flue gas.