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Synthetic route for Cu purpurin complexes and crystal structure of CuPP Thermal ellipsoids are shown at the 50% probability level. Parts of hydrogen atoms and TBA cations are not shown for clarity.
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CO 2 reduction through artificial photosynthesis represents a prominent strategy toward the conversion of solar energy into fuels or useful chemical feedstocks. In such configuration, designing highly efficient chromophores comprising earth-abundant elements is essential for both light harvesting and electron transfer. Herein, we report that a copp...
Citations
... Heterogeneous single-atom catalysts (SACs) are catalysts that have a precise atomic structure and include stable and reactive active centers made up of individual metal atoms, such as iron (Fe), cobalt (Co), or platinum (Pt), which are anchored to the substrate [9]. The active sites of single-atom catalysts (SACs) are typically individual metal atoms or clusters, which are different from metal-nitrogen-carbon (M-N-C) catalysts or molecular catalysts that depend on metal clusters or complexes [10,11]. Metal-nitrogencarbon (M-N-C) catalysts form complex active sites by coordinating metal atoms with nitrogen and carbon atoms inside a support structure. ...
The extensive use of single-atom catalysts (SACs) has appeared as a significant area of investigation in contemporary study. The single-atom catalyst, characterized by its maximum atomic proficiency and great discernment of the transition-metal center, has a unique combination of benefits from both heterogeneous and homogeneous catalysts. Consequently, it effectively bridges the gap between these two types of catalysts, leveraging their distinctive features. The utilization of SACs immobilized on graphene substrates has garnered considerable interest, primarily because of their capacity to facilitate selective and efficient photocatalytic processes. This review aims to comprehensively summarize the progress and potential uses of SACs made from graphene in photocatalytic carbon dioxide (CO2) reduction and hydrogen (H2) generation. The focus is on their contribution to converting solar energy into chemical energy. The present study represents the various preparation methods and characterization approaches of graphene-based single-atom photocatalyst This review investigates the detailed mechanisms underlying these photocatalytic processes and discusses recent studies that have demonstrated remarkable H2 production rates through various graphene-based single-atom photocatalysts. Additionally, the pivotal roleof theoretical simulations, likedensity functional theory (DFT), to understand the structural functional relationships of these SACs are discussed. The potential of graphene-based SACs to revolutionize solar-to-chemical energy conversion through photocatalytic CO2 reduction and H2 production is underscored, along with addressing challenges and outlining future directions for this developing area of study. By shedding light on the progress and potential of these catalysts, this review contributes to the collective pursuit of sustainable and efficient energy conversion strategies to mitigate the global climate crisis.
... Due to its abundance, affordability, and eco-friendliness, solar energy is widely regarded as a highly promising source of energy [6,7]. It is imperative to prioritize the development of methodologies for the conversion of solar energy into fossil fuels through photocatalytic CO 2 reduction employing CO 2 and water (H 2 O) as well as the elimination of organic pollutants [8,9]. ...
... Besides, selective production of multicarbon species remains a huge challenge over the currently dominant C1 chemicals. Moreover, the competitive H 2 evolution reaction further limits the selectivity in numerous studies 63,65,73,160 . ...
Using sunlight to power CO2 conversion into value-added chemicals and fuels is a promising technology to use anthropogenic CO2 emissions for alleviating our dependence on fossil fuels. In this Primer, we provide a holistic step-by-step guide for the experimentation of photocatalytic CO2 reduction, including catalyst synthesis and characterization, reactor construction, photocatalytic testing and mechanism exploration. We compare and analyse the state-of-the-art results with different photocatalysts and discuss possible reaction mechanisms. Furthermore, important considerations regarding practical application of photocatalytic CO2 reduction are highlighted and strategies to enhance energy conversion efficiency and product selectivity are summarized. This Primer also reveals current issues of reproducibility, standardizes data reporting and proposes a unified operation condition. Finally, future directions are outlined in terms of experiments, calculations, big-data development and practical application.
... During the CO 2 photoreduction reaction, a reduced Ni(I) intermediate is produced, which is coordinated with a terpyridine ligand, CO 2 , and solvent molecules (acetonitrile) to generate a penta-coordinated species that ultimately enables CO 2 reduction to CO. In another study, a copper purpurin complex was developed as a catalyst [147]. This complex contained an additional redox-active center, which enabled it to shift the reduction potential to 540 mV less than that of its organic dye component. ...
... This complex contained an additional redox-active center, which enabled it to shift the reduction potential to 540 mV less than that of its organic dye component. When this copper photosensitizer was combined with an iron porphyrin catalyst and sacrificial reductant, the system achieved a remarkable turnover number (TON) of 16,100 for the reduction of CO 2 to CO, with a very high selectivity for CO [147]. ...
Artificial photosynthesis is a technology with immense potential that aims to emulate the natural photosynthetic process. The process of natural photosynthesis involves the conversion of solar energy into chemical energy, which is stored in organic compounds. Catalysis is an essential aspect of artificial photosynthesis, as it facilitates the reactions that convert solar energy into chemical energy. In this review, we aim to provide an extensive overview of recent developments in the field of artificial photosynthesis by catalysis. We will discuss the various catalyst types used in artificial photosynthesis, including homogeneous catalysts, heterogeneous catalysts, and biocatalysts. Additionally, we will explore the different strategies employed to enhance the efficiency and selectivity of catalytic reactions, such as the utilization of nanomaterials, photoelectrochemical cells, and molecular engineering. Lastly, we will examine the challenges and opportunities of this technology as well as its potential applications in areas such as renewable energy, carbon capture and utilization, and sustainable agriculture. This review aims to provide a comprehensive and critical analysis of state-of-the-art methods in artificial photosynthesis by catalysis, as well as to identify key research directions for future advancements in this field.
... A significant advantage of leaning toward heterogeneous catalysts is the facile catalyst recovery after the reaction cycles. Alternatively, homogeneous photocatalysts such as supramolecular complexes or dissolved light-absorbing photoactive phases in the reactant media have been extensively exploited in this field, too, in photodegradation reactions (solar-photo Fenton) and CO 2 reduction [46][47][48]. Nonetheless, it is our aim to focus our discussion on the heterogeneous systems, which are economically preferred and present more implementation opportunities in 3D-printing. ...
... To provide a potentially widespread implementation, accelerating progress has been made in the development of inexpensive PSs to perform the same catalytic reaction 20 . Recently, PSs based on first-row transition metals such as Cu [21][22][23][24] and Zn 25 have been studied for light-driven CO 2 reduction, with turnover numbers (TONs) of 40-1566. Due to being readily available in nature and because they are synthetically easy to functionalize, organic PSs are promising alternative light-absorbers for photocatalytic CO 2 reduction [26][27][28] . ...
... Tuning the electron donors and acceptors in organic dyes help increasing the power conversion efficiencies of dye-sensitized solar cells 51,52 . We recently demonstrated that the coordination of polyhydroxy-anthraquinones to a redox active Cu center effectively enhanced the photocatalytic activity in both proton and CO 2 reductions 22,53 . In the present study, we report the application of simple yet more active aminoanthraquinone organic PSs 1-6 ( Fig. 1) for visible light-driven reduction of CO 2 to CO. Different from previous systems, high TONs for both the PS and the catalyst can be realized. ...
... The activity of CO 2 reduction by PSs 1-6 was studied in CO 2 -saturated DMF solutions under irradiation with a white light-emitting diode (LED, λ > 400 nm, 100 mW/cm 2 ). FeTDHPP ( Fig. 1) was used as the CO 2 reduction catalyst, for the reason that it has been demonstrated to provide high activity in photocatalytic systems from our previous study 22 ...
The direct utilization of solar energy to convert CO2 into renewable chemicals remains a challenge. One essential difficulty is the development of efficient and inexpensive light-absorbers. Here we show a series of aminoanthraquinone organic dyes to promote the efficiency for visible light-driven CO2 reduction to CO when coupled with an Fe porphyrin catalyst. Importantly, high turnover numbers can be obtained for both the photosensitizer and the catalyst, which has not been achieved in current light-driven systems. Structure-function study performed with substituents having distinct electronic effects reveals that the built-in donor-acceptor property of the photosensitizer significantly promotes the photocatalytic activity. We anticipate this study gives insight into the continued development of advanced photocatalysts for solar energy conversion.
... 7b,45 These metrics are comparable to those state-of-the-art noble-metal-free molecular systems for photocatalytic CO 2 reduction, in which most cases produced a TON of <10 4 (Table S13); it is noteworthy that only a Cu(II)-purpurin/Fe(III)-porphyrin system yielded a higher TON of 16100 but a lower selectivity (95%). 46 Overall, these pioneering catalytic performances demonstrate the great promise of the Al(III)-sensitized noble-metal-free systems. ...
Exploiting noble-metal-free systems for high-performance photocatalytic CO2 reduction still presents a key challenge, partially due to the long-standing difficulties in developing potent and durable earth-abundant photosensitizers. Therefore, based on the very cheap aluminum metal, we have deployed a systematic series of homoleptic Al(III) photosensitizers featuring 2-pyridylpyrrolide ligands for CO2 photoreduction. The combined studies of steady-state and time-resolved spectroscopy as well as quantum chemical calculations demonstrate that in anerobic CH3CN solutions at room temperature, visible-light excitation of the Al(III) photosensitizers leads to an efficient population of singlet excited states with nanosecond-scale lifetimes and notable emission quantum yields (10-40%). The results of transient absorption spectroscopy further identified the presence of emissive singlet and unexpectedly nonemissive triplet excited states. More importantly, the introduction of methyl groups at the pyrrolide rings can greatly improve the visible-light absorption, reducing power, and durability of the Al(III) photosensitizers. With triethanolamine, BIH (1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole), and an Fe(II)-quaterpyridine catalyst, the most methylated Al(III) photosensitizer achieves an apparent quantum efficiency of 2.8% at 450 nm for selective (>99%) CO2-to-CO conversion, which is nearly 28 times that of the unmethylated one (0.1%) under identical conditions. The optimal system realizes a maximum turnover number of 10250 and higher robustness than the systems with Ru(II) and Cu(I) benchmark photosensitizers. Quenching experiments using fluorescence spectroscopy elucidate that the photoinduced electron transfer in the Al(III)-sensitized system follows a reductive quenching pathway. The remarkable tunability and cost efficiency of these Al(III) photosensitizers should allow them as promising components in noble-metal-free systems for solar fuel conversion.
... Thus, we considered that the o-quinone form of purpurin, which is generated via purpurin autoxidation accompanied by Cu(I)/Cu(II) redox cycle, could lead to DNA adducts and piperidine-labile sites (Fig. 5). Although a recent study has reported that purpurin can react with Cu(II) generating a metal complex (2:1) under certain conditions [26], the complex was not detected by ultraviolet-visible spectroscopy under our conditions (data not shown). ...
Background
Purpurin (1,2,4-trihydroxy-9,10-anthraquinone), a natural red anthraquinone pigment, has historically been used as a textile dye. However, purpurin induced urinary bladder tumors in rats, and displayed a mutagenic activity in assay using bacteria and mammalian cells. Many carcinogenic dyes are known to induce bladder cancers via DNA adduct formation, but carcinogenic mechanisms of purpurin remain unknown. In this study, to clarify the mechanism underlying carcinogenicity of purpurin, copper-mediated DNA damage induced by purpurin was examined using ³² P-labeled DNA fragments of human genes relevant to cancer. Furthermore, we also measured 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG), an indicator of oxidative DNA damage, in calf thymus DNA.
Results
Purpurin plus Cu(II) cleaved ³² P-labeled DNA fragments only under piperidine treatment, indicating that purpurin caused base modification, but not breakage of the DNA backbone. In the absence of Cu(II), purpurin did not induce DNA cleavage even with piperidine treatment. Purpurin plus Cu(II) caused piperidine-labile sites predominantly at G and some T residues. Bathocuproine, a Cu(I) chelator, completely prevented the occurrence of piperidine-labile sites, indicating a critical role of Cu(I) in piperidine-labile sites induced by purpurin plus Cu(II). On the other hand, methional, a scavenger of a variety of reactive oxygen species (ROS) and catalase showed limited inhibitory effects on the induction of piperidine-labile sites, suggesting that ROS could not be major mediators of the purpurin-induced DNA damage. Considering reported DNA adduct formation by quinone metabolites of several carcinogenic agents, quinone form of purpurin, which is possibly generated via purpurin autoxidation accompanied by Cu(I)/Cu(II) redox cycle, might lead to DNA adducts and piperidine-labile sites. In addition, we measured contents of 8-oxodG. Purpurin moderately but significantly increased 8-oxodG in calf thymus DNA in the presence of Cu(II). The 8-oxodG formation was inhibited by catalase, methional and bathocuproine, suggesting that Cu(I)-hydroperoxide, which was generated via Cu(I) and H 2 O 2 , caused oxidative DNA base damage.
Conclusions
We demonstrated that purpurin induces DNA base damage possibly mediated by Cu(I)/Cu(II) redox cycle both with and without ROS generation, which are likely to play an important role in its carcinogenicity.
... imidazole) as a sacrificial reductant, CuPP (copper porphyrin) as a photosensitizer, FeTDHPP (iron porphyrin) as a catalyst. This system showed over than 16100 turnover number of CO from CO 2 , (Yuan et al., 2021). (b): Photocatalytic conversion of CO 2 under visible light on polymeric cobalt phthalocyanine coated on g-C 3 N 4 . ...
... However, the combination of CPs with other semiconductor oxides or with metal NPs or metal cations brings enhanced photonic properties and synergism. Recently, Yuan et al. (2021) reported that molecular copper purpurin chromophore can achieve efficient photocatalytic conversion of CO 2 to CO with a 95% selectivity as reported in Fig. 3a. Among the reported CPs, g-C 3 N 4 was one of the most studied for CO 2 photoconversion as a photocatalyst, capture or/and activation support (Kumar et al., 2020a;Lin et al., 2014;Liu et al., 2020;Roy and Reisner, 2019;Yang et al., 2021). ...
... (a): Mechanism of CO 2 photoconversion promoted by molecular copper purpurin chromophore under visible light, BIH (1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole) as a sacrificial reductant, CuPP (copper porphyrin) as a photosensitizer, FeTDHPP (iron porphyrin) as a catalyst. This system showed over than 16100 turnover number of CO from CO 2 , reproduced with permission from Ref(Yuan et al., 2021). (b): Photocatalytic conversion of CO 2 under visible light on polymeric cobalt phthalocyanine coated on g-C 3 N 4 . ...
... The total inorganic carbon (TIC) concentration was measured and monitored during the photocatalytic reactions (t = 0, t = 15, and t = 300 min). The results of TIC analysis confirmed that cyanate was completely decomposed in the presence of nano-TiO 2 /FeCl 3 (Rej et al., 2021;Yuan et al., 2021) (details Table 1 Life cycle inventory data of the degradation of 98% cyanate from 1 L wastewater via three approaches of nano-TiO 2 /FeCl 3 photocatalysis. of the analytical measurements of cyanate by-products are provided in supplementary Appendix A; Table A1). ...
Mitigating the environmental health impact associated with cyanate is one of the key challenges facing local communities and the mining industry. Cyanate and cyanide are often found as co-contaminants in the environment. However, there is a lack of comprehensive research on the life cycle assessment (LCA) of photocatalytic cyanate degradation. This study aims to assess the environmental impacts of cyanate degradation by nano-TiO2/FeCl3 photocatalysis and compare the life cycle impacts of UV-A-, visible-, and solar-driven photocatalysis. The functional unit of the LCA involves “the degradation of 98% cyanate from 1 L wastewater by nano-TiO2/FeCl3.” In the synthesis of TiO2 photocatalysts, the IMPACT 2002+ LCA method reveals that aquatic ecotoxicity, non-renewable energy, terrestrial ecotoxicity, and global warming are the main contributors to total environmental damage through cyanate removal by nano-TiO2/FeCl3 photocatalysis. Ethanol and electricity consumption generates higher environmental impacts than other inputs. The results of endpoint analysis highlight that climate change associated with electricity contributes the greatest environmental impact across the entire photocatalysis life cycle for cyanate removal under all different irradiation sources. This study provides deeper insight into the life cycle environmental hotspots of photocatalytic cyanate degradation by nano-TiO2, potentially enabling mining operators and stakeholders to achieve resource efficiency and cleaner production.
