Abstract
It is a great challenge to convert thermochemically stable CO
2
into value-added products such as CH
4
, CH
3
OH, CO via utilizing solar energy. It is also a difficult task to develop an ...efficient catalyst for the reduction of CO
2
. We have designed and synthesized noble metal-free photocatalytic nanostructure Ni
2
P/CdS and Pt/TiO
2
for conversion of CO
2
to methanol in the presence of sacrificial donor triethylamine (TEA) and hydrogen peroxide. The synthesised catalysts physicochemical properties were studied by using several spectroscopic techniques like; XRD, UV-DRS, XPS, TEM, SEM and PL. Quantification of methanol by GC–MS showed encouraging results of 1424.8 and 2843 μmol g
−1
of catalyst for Pt/TiO
2
and 5 wt% Ni
2
P/CdS composites, respectively. Thus, Ni
2
P/CdS is a promising catalyst with higher productivity and significant selectivity than in-vogue catalysts.
TONs of copper fun: There is considerable interest in developing catalysts to harness the abundant natural supply of methane for various industrial applications. Two tricopper complexes capable of ...mediating efficient oxidation of methane to methanol under ambient conditions were tested: a biomimetic tricopper complex (see figure) and a tricopper‐peptide species derived from the particulate methane monooxygenase (pMMO) protein.
The tricopper complex Cu I Cu I Cu I ( 7-N-Etppz ) 1+ , where 7-N-Etppz denotes the ligand 3,3′-(1,4-diazepane-1,4-diyl)bis1-(4-ethyl piperazine-1-yl)propan-2-ol, is capable of mediating facile ...conversion of methane into methanol upon activation of the tricopper cluster by dioxygen and/or H 2 O 2 at room temperature. This is the first molecular catalyst that can catalyze selective oxidation of methane to methanol without over-oxidation under ambient conditions. When this Cu I Cu I Cu I tricopper complex is activated by dioxygen or H 2 O 2 , the tricopper cluster harnesses a “singlet oxene”, the strongest oxidant that could be used to accomplish facile O-atom insertion across a C–H bond. To elucidate the properties of this novel catalytic system, we examine here methane oxidation over a wider range of conditions and extend the study to other small alkanes, including components of natural gas. We illustrate how substrate solubility, substrate recognition and the amount of H 2 O 2 used to drive the catalytic oxidation can affect the outcome of the turnover, including regiospecificity, product distributions and yields of substrate oxidation. These results will help in designing another generation of the catalyst to alleviate the limitations of the present system.
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•S-nZVI showed better removal of both As(III) and As(V) than nZVI in anoxic condition.•The S/Fe molar ratio significantly influenced the removal rate of As.•FeS layer alleviated the ...surface passivation and increased the longevity of nZVI.•The possible removal mechanism of As by S-nZVI was illustrated.
Sulphur modified nano zerovalent iron (S–nZVI) has shown considerable promise for removal of various aqueous contaminants. However studies utilizing S–nZVI for removal of aqueous inorganic arsenic (As) is relatively rare, which was studied in this work. Characterization of the synthesized S–nZVI showed typical core-shelled structure with distorted outer shell consisting of iron oxide and FeS. The removal rate of both As(III) and As(V) by S–nZVI was considerably enhanced compared to nZVI and highest As removal was observed at S/Fe ratio of 0.1 under acidic condition. Results showed slight decrease in As removal efficiencies for S–nZVI aged upto 48 h, with obvious drop in As removal efficiencies for longer aging time which although still exhibited higher reactivity than bare nZVI. Spectroscopic investigation showed sulphur amendment of nZVI completely altered the As sequestration mechanism compared to nZVI. While reduction of the adsorbed As(III) and As(V) was observed for bare nZVI, in contrast, uptake of As(III) and As(V) by S–nZVI involves adsorption as As(III) and As(V) oxyanion respectively with additional precipitation of As2S3. Overall, the study shows that incorporation of FeS on the surface of nZVI can be an effective modification strategy for efficient sequestration of As from contaminated water.
Water, the most fundamental source of life, is contaminated by various organic pollutants, especially organic dyes from the dying industry. The photocatalytic degradation of malachite green (MG) was ...studied using a zinc-based metal-organic framework (Zn-BTC MOF) and ZnO. Thermally decomposing Zn-MOF synthesized ZnO and its structural and optical properties were analyzed using various spectroscopic techniques. This article focuses primarily on the wavelength-dependent photoluminescence properties of Zn-MOF and ZnO materials and their role in the photocatalytic degradation of MG dye in water. Zn-MOF and ZnO photocatalysts exhibited a photodegradation efficiency of approximately 99% after 40 min of visible light exposure. Based on kinetic experiments, the degrading efficiency of these catalysts followed pseudo-first-order reaction kinetics with a correlation of R2 = 0.99 and a rate constant of 0.031 min−1. This manuscript is helpful to researchers working on ZnO and Zn-MOF materials for photocatalytic and environmental applications.
•Photoluminescence is an important and frequently reported property of Metal-Organic Frameworks (MOFs).•This communication is primarily concerned with the luminescence properties of Zn-MOF and ZnO materials.•Zn-MOF and ZnO role in the photodegradation of recalcitrants such as malachite green (MG) in water.•These catalysts displayed photodegradation efficiency of about 95% within 40 min.
•Preparation and characterization of CdS-anchored CuBTC MOF (CuMC) for selective photocatalytic reduction of CO2 to CH3 OH.•The CuMC2 photocatalyst effectively promotes photo-splitting of H2 O2 to ...produce nascent hydrogen atoms (H•).•H• preferentially react with CO2 to form CH3 OH over recombination to form H2 gas.•The CuMC2 composite is capable of converting CO2 into CH3 OH with a quantum efficiency approaching 80%.•ESR and 13 C NMR experiments provide direct evidence for the photo-splitting of H2 O2 to produce the H• radicals.•A novel mechanism for the selective conversion of CO2 into CH3 OH is revealed.
Photo-splitting of H2O2 in visible light is achieved by Cu-MOFs of Cu nodes and 1, 3, 5-benzene tricarboxylic acid (BTC) organic linkers (CuM) decorated with CdS (C) at varying concentrations of CdS in the CuMC composite. This process produces abundant nascent hydrogen atoms to promote the efficient catalytic reduction of CO2 to methanol (CH3OH) in visible light. The slow rate of recombination of the nascent hydrogen atoms produced by the H2O2 photo-splitting on the surface of the CdS quantum dots ensures a high steady-state concentration of hydrogen atoms with significantly reduced production of the less reactive hydrogen gas. With slow recombination of the photo-generated charges and the large surface areas for CO2 adsorption by the MOF, one of the CuMC composites is capable of convertingCO2 into CH3OH with a quantum efficiency approaching 80 %. A mechanism for the selective conversion of CO2 into CH3OH is proposed.
Two complexes of the type Co(en)
2IP
3+ (IP
=
imidazo4,5-f1,10-phenanthroline) and Co(en)
2PIP
3+(PIP
=
2-phenylimidazo4,5-f1,10-phenanthroline) have been synthesized and characterized by UV–VIS, IR ...and
1H NMR spectral methods. Absorption spectroscopy, emission spectroscopy, viscosity measurements and DNA melting techniques have been used to investigate the binding of these two complexes with calf thymus DNA and photocleavage studies have been used to investigate the binding of these complexes with plasmid DNA. The spectroscopic studies together with viscosity measurements and DNA melting studies support that complexes
1 and
2 bind to CT DNA(=calf thymus DNA) by an intercalation mode via IP or PIP into the base pairs of DNA. Complex
2 binds more avidly to CT DNA than
1, which is consistent with the extended planar ring π system of PIP. Noticeably, the two complexes have been found to be efficient photosensitisers for strand scissions in plasmid DNA.
Two complexes of the type Co(en)
2IP
3+ (IP
=
imidazo4,5-f1,10-phenanthroline) and Co(en)
2PIP
3+ (PIP
=
2-phenylimidazo4,5-f1,10-phenanthroline) have been synthesized and characterized by UV–VIS, IR and
1H NMR spectral methods. Absorption spectroscopy, emission spectroscopy, viscosity measurements and DNA melting techniques have been used to investigate the binding of these two complexes with calf thymus DNA and photocleavage studies have been used to investigate the binding of these complexes with plasmid DNA. The spectroscopic studies together with viscosity measurements and DNA melting studies support that complexes
1 and
2 bind to CT DNA(=calf thymus DNA) by an intercalation mode via IP or PIP into the base pairs of DNA. Complex
2 binds more avidly to CT DNA than
1, which is consistent with the extended planar ring π system of PIP. Noticeably, the two complexes have been found to be efficient photosensitisers for strand scissions in plasmid DNA.
•The photocatalytic performance of the GO@ZnMOF composite was tested by degrading the antibiotics ciprofloxacin (CIP) and tetracycline (TC).•The degradation efficiency for CIP and TC is more with ...CaO2 compared to H2O2 by virtue of CaO2 continuously producing H2O2.•Introducing H2O2 or CaO2 encourages the formation of more active reactive oxygen species (ROS).•Radical scavenging experiments confirmed that the degradation reaction mimics the photo-Fenton reaction.•The photodegradation with CaO2 is more significant (99%) than H2O2 (87%) because CaO2 provides H2O2 for a longer time.
A robust Zn-BTC MOF photocatalyst deposited with varying concentrations of graphene oxide was successfully prepared using an in-situ solvothermal method and named GO@ZnMC. X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and other techniques were used to characterize the phase component, microstructure, and optical properties of the catalysts. The photocatalytic performance of the GO@ZnMC composite was tested by degrading the antibiotics ciprofloxacin (CIP) and tetracycline (TC) with the help of hydrogen peroxide (H2O2) or calcium peroxide (CaO2) under visible light irradiation. The degradation efficiency for CIP and TC is more with CaO2 compared to H2O2 by virtue of CaO2 continuously producing H2O2. The degradation rate of the GO@ZnMC3 composite is higher when compared to that of pristine GO, Zn-MOF, and other composites. The increased photocatalytic activity is attributed to the formation of heterojunction that effectively suppresses electron-hole pair recombination. Introducing H2O2 or CaO2 encourages the formation of more active reactive oxygen species (ROS), specifically OH•, as confirmed by radical scavenging experiments, showing that the degradation reaction mimics the photo-Fenton reaction. A possible photocatalytic degradation mechanism is also proposed with the help of the LC-MS analysis. The catalyst is stable and reusable until four catalytic cycles.
Mineral carbonation in aqueous solutions presents a pragmatic avenue for tackling the challenges associated with carbon capture, utilisation, and storage, particularly in limiting global temperature ...rise to 1.5 °C for climate change mitigation. The urgency to engineer the removal of atmospheric CO
2
has driven the exploration of innovative methods for direct conversion into valuable products, with a specific emphasis on calcite as a promising approach for carbon dioxide sequestration. This investigation focuses on the biomimetic strategy of emulating the catalytic activity of carbonic anhydrase by synthesizing a zinc-based metal-organic framework. The MOF, synthesized with Zinc as the central metal coordinated by 1,2,3-benzene tricarboxylic acid, displays noteworthy structural adaptability, diversity, and an extensive surface area. The characterisation of synthesised materials through UV DRS, XRD, XPS, FTIR, SEM, and Raman analyses corroborates its structural features. A comparative study with a Nickel-based MOF (Ni-BTC-MOF) underscores the advantages of zinc over nickel in CO
2
mineralisation experiments. Remarkably, Zn-BTC-MOF demonstrates superior catalytic activity, reusability, solvent compatibility, and thermal stability compared to Ni-BTC-MOF. The Zn-BTC-MOF catalyst achieves a mineralisation yield of 25 mg, comparable with the reported results for natural carbonic anhydrase (34.92 mg) and imidazole-carbonic anhydrase (21.55 mg). The Zn-BTC-MOF catalyst displays exceptional reusability, maintaining CO
2
mineralisation activity across over a broad pH and temperature range. These findings underscore the potential of Zn-BTC-MOF as an effective biomimetic catalyst for carbon dioxide mineralisation, holding promising applications in carbon capture and utilization technologies.
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