Single cobalt atom anchored on carbon nitride with well-defined active sites for photo-enzyme catalysis

doi:10.1016/j.nanoen.2020.104750

Nano Energy

Volume 73, July 2020, 104750

https://doi.org/10.1016/j.nanoen.2020.104750 Get rights and content

Highlights

•
Atomically dispersed Co sites on carbon nitride nanosheets (Co₁/C₃N₄) were synthesized by crystal-assisted confinement pyrolysis approach.
•
Co₁/C₃N₄ manifested extraordinary performance for photocatalytic NADH regeneration, which could integrate the photo and enzyme catalysis.
•
The Co₁ in Co₁/C₃N₄ catalyst was found to interact with Cp* of Rh-based redox mediator in the form of CoN₃-Cp* moieties.

Abstract

By analogy to mono-nuclear metalloenzymes, single-atom dispersed catalysts (SACs) demonstrate very promising performance for many conventional heterogeneous and homogeneous reactions. However, the prospect of integrating SACs with enzymatic catalysis is still unexplored. Herein, atomically dispersed Co sites on ultrathin two-dimensional (2D) carbon nitride nanosheets (Co₁/C₃N₄) were constructed and applied for efficiently photochemical cofactor (NADH) regeneration. The NADH regeneration yield reached as high as 99%. Subsequently, the in-situ regenerated-NADH triggered alcohol dehydrogenase for enzymatic reduction of aldehyde where 100% alcohol yield was achieved. Using atomic spectroscopy characterization and theoretical calculation, the genuine active sites of Co₁/C₃N₄ catalyst in reaction system were revealed in the form of CoN₃-Cp* moieties (Cp*, 1,2,3,4,5-pentamethylcyclopentadiene). Such a well-defined atomic catalyst opens a new avenue for the organic transformation application of single-atom catalysts in enzyme catalysis.

Graphical abstract

Introduction

Recently, Single-atom catalysts (SACs), defined as the isolated single-atom catalytic active sites stabilized by a underlying support, have become new frontiers in catalysis community [[1], [2], [3]]. By analogy to mono-nuclear metalloenzymes, SACs provide a good platform to not only understand the structure-reactivity relationship at atomic scale, but also to integrate the merits of heterogeneous catalysis, homogeneous catalysis and even enzymatic catalysis [4]. In fact, SACs have been demonstrated to have excellent performance for many typical heterogeneous and homogeneous reactions, including industrial reactions [5,6], organic transformation [[7], [8], [9], [10]], electrochemical process [[11], [12], [13]], photocatalytic reactions [[14], [15], [16]]. However, enzymatic catalysis process has not yet been coupled with SACs because enzymes easily encounter fatal deactivation by heavy metals, high temperature and organic solvents [17]. And enzymatic reaction usually involves complex macromolecule substrates, which requires multiple active sites to synergistically catalytic conversion while SACs only have one kind of catalytic active sites.

Oxidoreductase, as one of the largest classes of enzymes, is widely utilized in industrial biocatalysis for the synthesis of fine chemicals and new drugs [18]. However, most of these enzymatic reductions depend on the participation of cofactors (or coenzyme), which were stoichiometrically consumed during the redox cycles (e.g., NADH→NAD⁺, molecular structures given in Fig. S1) [19]. For industrial applications, in-situ NADH regeneration is indispensable to provide a reducing power for driving many redox enzymatic cycles. Previously, several methods for NADH regeneration including electrochemical regeneration [20], chemical regeneration [21,22], and enzymatic regeneration [22] were established, respectively. Nevertheless, these methods suffer from high cost, low selectivity or poor NADH yield. Notably, photocatalytic NADH regeneration especially by graphitic carbon nitride materials has attracted great attention in the past several years [[23], [24], [25], [26]]. Recently, anchoring Rh complex (redox mediator in NADH regeneration) onto heterogeneous supports (for example, periodic mesoporous organosilica [27], MOFs [28]) via rigid synthesis procedures was realized in the chemical or electrochemical regeneration route for the sake of enhancing the bio-compatibility of the systems. However, the systematic integration between homogeneous Rh complex catalysis, heterogeneous carbon nitride photocatalysis and the sustained enzymatic synthesis is still very challenging.

Herein, we designed and synthesized atomically dispersed Co sites on ultrathin two-dimensional (2D) carbon nitride nanosheets (denoted as Co₁/C₃N₄) through a crystal-assisted confinement pyrolysis method. By employing the Co₁/C₃N₄ as the photocatalyst for the NADH regeneration, the high yield and selectivity could be obtained in the presence of [Cp*Rh(bpy)(H₂O)]²⁺ (abbreviated as M) as the electron and proton mediator. Subsequently, the enzymatically active 1,4-NADH can be smoothly consumed by alcohol dehydrogenase, achieving enzymatic reduction of benzaldehyde to benzyl alcohol with 100% selectivity (Scheme 1). The enzymatic reduction can be reused for at least 3 times without catalyst deactivation. More importantly, the homogeneous M complex was found to be anchored on the surface of this atomic Co₁/C₃N₄ catalyst (denoted as Co₁/C₃N₄–Rh catalyst), which was probably due to the unsaturated Co coordination. The integrated active sites were further revealed in the form of CoN₃-Cp* moieties (Cp*, 1,2,3,4,5-pentamethylcyclopentadiene) by X-ray absorption fine structure spectroscopy analysis and theoretical calculation. Surprisingly, this Co₁/C₃N₄–Rh catalyst could still exhibit superior enzymatic reduction performance without adding fresh Rh complex. To the best of our knowledge, this is the first report that atomic active sites in SACs could accomplish the enzyme-related organic transformation and realize the integration of homogeneous, heterogeneous and enzymatic catalysis.

Section snippets

Catalysts preparation and structural characterization

In this work, ultrathin and 2D carbon nitride nanosheets with uniform atomic Co dopants featuring abundant open active sites were obtained via crystal-assisted confinement pyrolysis method (Fig. 1a). In a typical synthesis, cobalt precursor, dicyanamide (DCD) and NaCl (crystallite template) were mixed together in aqueous solution and then frozen with liquid nitrogen, forming the Co-DCD@NaCl precursor. In this step, NaCl molecules rapidly grew into crystals while Co-DCD complex was supported on

Conclusion

In summary, we successfully synthesized atomic Co dopants onto the ultrathin 2D carbon nitride matrix via crystal-assisted confinement pyrolysis method. The as-prepared Co₁/C₃N₄ single-atom catalyst manifested extraordinary performance for photo-catalytic NADH regeneration and efficiently accomplished NADH-dependent enzymatic reduction of benzaldehyde to benzyl alcohol. Furthermore, by incubating rhodium complex with Co₁/C₃N₄ single-atom catalyst, the obtained Co₁/C₃N₄–Rh photocatalyst could

Chemicals and materials

Co(OAc)₂, benzaldehyde, NaCl were purchased from Sinopharm Chemical Reagent, dicyandiamide and [Cp*RhCl₂]₂ were obtained from Aladdin. NaH₂PO₄ and Na₂HPO₄ were obtained from Energy Chemicals. Alcohol Dehydrogenase and oxidized nicotinamide adenine dinucleotide (NAD⁺) were purchased from Sigma-Aldrich.

Synthesis of [Cp*Rh(bpy)H₂O]²⁺

Pentamethylcyclopentadienyl rhodium bipyridine ([Cp*Rh(bpy)(H₂O)]²⁺) was synthesized using the procedure reported previously [25]: [Cp*RhCl₂]₂ was suspended in methanol. The suspension turned into

CRediT authorship contribution statement

Wengang Liu: Conceptualization, Funding acquisition, Data curation, Investigation, Project administration, Formal analysis, Writing - original draft, Writing - review & editing. Wenjuan Hu: Data curation, Resources, Validation. Lijun Yang: Data curation, Resources, Validation. Jian Liu: Supervision, Conceptualization, Funding acquisition, Project administration, Writing - original draft, Writing - review & editing.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The authors are grateful to the supports from the National Natural Science Foundation of China (21902082, 21802080), the Original Innovation Project of Qingdao City (19-6-2-72-cg), the Distinguished Young Scholar Fund of Natural Science Foundation of Shandong Province (ZR2019JQ05), the Key Basic Research Project of the Natural Science Foundation of Shandong Province (ZR2019ZD47), the Education Department of Shandong Province (2019KJC006), the Doctoral Fund of QUST and the National Young

Wengang Liu is an assistant professor in the College of Material Science and Engineering at Qingdao University of Science and Technology. He received the B.S. degree (2013) in East China University of Science and Technology, and obtained his Ph.D. (2018) in Industrial Catalysis from Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Currently, his research focuses on design and synthesis for novel carbon-based single-atom catalyst and its application for industrial reactions.

References (35)

W. Liu et al.
Chem. Sci.
(2016)
G. Han et al.
Nano Energy
(2019)
Z. Zeng et al.
Nano Energy
(2020)
X. Wang et al.
Chem
(2017)
Y. Wang et al.
Appl. Catal., B
(2017)
X. Yang et al.
Acc. Chem. Res.
(2012)
B. Qiao et al.
Nat. Chem.
(2011)
J. Wang et al.
Adv. Mater.
(2018)
P.X. Liu et al.
Science
(2016)
A.M. Abdel-Mageed et al.
J. Am. Chem. Soc.
(2019)

R. Lang et al.

Angew. Chem. Int. Ed.

(2016)

Z. Zhang et al.

Nat. Commun.

(2017)

W. Liu et al.

J. Am. Chem. Soc.

(2017)

L. Zhang et al.

ACS Catal.

(2015)

W. Chen et al.

Angew. Chem. Int. Ed.

(2017)

Y. Ye et al.

ACS Catal.

(2017)

H. Zhang et al.

Angew. Chem. Int. Ed.

(2016)

Cited by (94)

Structure-phase transformation of bismuth oxide to BiOCl/Bi<inf>24</inf>O<inf>31</inf>Cl<inf>10</inf> shoulder-by-shoulder heterojunctions for efficient photocatalytic removal of antibiotic
2025, Journal of Environmental Sciences (China)
Developing heterojunction photocatalyst with well-matched interfaces and multiple charge transfer paths is vital to boost carrier separation efficiency for photocatalytic antibiotics removal, but still remains a great challenge. In present work, a new strategy of chloride anion intercalation in Bi₂O₃ via one-pot hydrothermal process is proposed. The as-prepared Ta-BiOCl/Bi₂₄O₃₁Cl₁₀ (TBB) heterojunctions are featured with Ta-Bi₂₄O₃₁Cl₁₀ and Ta-BiOCl lined shoulder-by-shouleder via semi-coherent interfaces. In this TBB heterojunctions, the well-matched semi-coherent interfaces and shoulder-by-shoulder structures provide fast electron transfer and multiple transfer paths, respectively, leading to enhanced visible light response and improved photogenerated charge separation. Meanwhile, a type-II heterojunction for photocharge separation has been obtained, in which photogenerated electrons are drove from the CB (conduction band) of Ta-Bi₂₄O₃₁Cl₁₀ to the both of bilateral empty CB of Ta-BiOCl and gathered on the CB of Ta-BiOCl, while the photogenerated holes are left on the VB (valence band) of Ta-Bi₂₄O₃₁Cl₁₀, effectively hindering the recombination of photogenerated electron-hole pairs. Furthermore, the separated electrons can effectively activate dissolved oxygen for the generation of reactive oxygen species (·O₂⁻). Such TBB heterojunctions exhibit remarkably superior photocatalytic degradation activity for tetracycline hydrochloride (TCH) solution to Bi₂O₃, Ta-BiOCl and Ta-Bi₂₄O₃₁Cl₁₀. This work not only proposes a Ta-BiOCl/Bi₂₄O₃₁Cl₁₀ shoulder-by-shoulder micro-ribbon architectures with semi-coherent interfaces and successive type-II heterojunction for highly efficient photocatalytic activity, but offers a new insight into the design of highly efficient heterojunction through phase-structure synergistic transformation strategy.
Single-atom copper anchored on algal-based carbon induce peroxydisulfate activation for tetracycline degradation: DFT calculation and toxicity evaluation
2024, Separation and Purification Technology
Single-atom catalysts have wide application prospects in peroxydisulfate (PDS)-based advanced oxidation process to degrade organic pollutants, but its catalytic performance is limited due to its cost, Metal-N coordination number, and single-atom loading amount. Herein, a novel nitrogen doped algal-based carbon confined single-atom copper catalyst (Cu–N/C-SAC_(S)) was synthesized using molten salt assisted pyrolysis and coupling with PDS to degrade tetracycline (TC). AC-HAADF-STEM and XAFS analysis proved that single atom Cu was loaded (Content 1.9 %) successfully and coordinated with two N and two C. XPS and XANES spectra analysis suggested that Cu atoms mainly existed in a positive divalent state in Cu–N/C-SAC_(S). When the catalyst dosage of Cu–N/C-SAC_(S) was 0.1 g/L, TC was almost completely removed. Moreover, Cu–N/C-SAC_(S) had a broad pH adaptation range and strong ability against interference. Singlet oxygen (¹O₂), superoxide radicals (•O₂⁻), and electron transfer had an important contribution for TC removal. DFT calculations confirmed that the activation process of Cu–N/C-SAC_(S) producing SO₄^•− was easier than the nitrogen doped blue-green algal-based carbon (N-BGAC). In addition, Cu–N/C-SAC_(S) possessed good recyclability and stability. The main degradation pathways of TC were analyzed, and the toxicity of the intermediates was calculated. This study provides a new solution strategy for the resource utilization of waste biomass, and provides technical support and theoretical guidance for the efficient application of single-atom catalysts in organic wastewater.
Pickering emulsion stabilized with charge separation and transfer modulated photocatalyst for enzyme-photo-coupled catalysis
2024, Chinese Journal of Catalysis
Biocatalytic reduction is extensively employed in chemical and pharmaceutical industries due to its notable advantages including high activity, selectivity and mild reaction conditions, however, the stoichiometric use of the expensive NADH (reduced form of nicotinamide adenine dinucleotide) hinders its widespread application. Despite the persisting challenges of low charge separation efficiency and limited solubility of organic substrates in aqueous phase, in situ photocatalytic NADH regeneration remains a promising solution. Herein, we report the construction of an enzyme-photo-coupled catalytic system in Pickering emulsion droplet, which was stabilized by a charge separation and transfer modulated photocatalyst. The photocatalyst integrated with visible light driven conjugated polymer, TiO₂ and electron mediator greatly enhanced the cascade electron transfer from photocatalyst to NAD⁺. Consequently, NADH production rate over the integrated photocatalyst reaches as high as 2.4 mmol·g⁻¹·h⁻¹ under visible light irradiation, 12 folds higher than the corresponding physical mixture. Furthermore, the enzyme-photo-coupled catalytic system was constructed with alcohol dehydrogenase/NAD⁺ confined in the emulsion droplet and photocatalyst assembled at the oil-water interface. The photoactive emulsion continuously catalyzed the n-butyaldehyde reduction to accumulate 16.1 mmol·L⁻¹ butanol, equivalent to 14 cycles for NADH regeneration under visible light irradiation. The primary result demonstrates the potential application prospect of Pickering emulsion in enzyme-photo-coupled catalysis due to the facilitated charge transfer from photocatalyst to NAD⁺ and fast mass diffusion attributed to the large interfacial area of water and oil.
Highly selective regeneration of 1,4-NADH enabled by a metal-free core-shell photocatalyst of resorcinol-formaldehyde resins@polyaniline under visible light
2024, Applied Catalysis B: Environmental
Cofactors, including reduced nicotinamide adenine dinucleotide (NADH), are involved in approximately 80 % of oxidoreductase-catalyzed reactions. However, NADH has not been widely used in the industrial production processes due to cost factors. In this work, we have designed a kind of metal-free core-shell photocatalyst with resorcinol-formaldehyde resin spheres as the core and polyaniline as the shell (RF@PANI) for the highly efficient and selective photocatalytic regeneration of 1,4-NADH (only 1,4-NADH has enzyme activity). It was demonstrated that the introduction of the carbonyl group and the sum of electronic effects made the C4 site of NAD⁺ a more electrophilic hydride transfer site rather than C6 and C2 in the RF@PANI system, leading to the high selectivity of NAD⁺ to 1,4-NADH. The discovery of this mechanism will guide the design of more efficient and highly selective catalysts to break through the cost limitations for the large-scale applications of NADH.
A brief review in preparation and applications of bimetallic single-atom catalysts in environmental advanced oxidation processes and energy sectors
2024, Inorganica Chimica Acta
Single-atom catalysts (SACs), have desired single metal atoms / active sites, that significantly enhanced kinetics for targeted reactions, such as environmental applications in advanced oxidation processes (AOPs) in Fenton-like/E-Fenton, photocatalysis and PEC (photo-electrochemical) systems for pollutants removal, and carbon emission reduction and carbon neutrality via Hydrogen evolution reaction (HER), via oxygen reduction reaction (ORR) in fuel cell and/or via CO₂ reduction reaction (CO₂RR) and Nitrogen/nitrate reduction reaction (NRR). The progress in the above research area is briefly summarized and investigated. The performances depend on the metal element, support substrate, and coordination status shaped in preparation. In fuel cells, the hydrogen production and the electrochemical reduction of O₂ and CO_2, SACs, especially bemetallic SACs, all demonstrated great potential.
Constructing a CdS QDs/silica gel composite with high photosensitivity and prolonged recyclable operability for enhanced visible-light-driven NADH regeneration
2023, Journal of Colloid and Interface Science
Visible-light-driven nicotinamide adenine dinucleotide (NADH) regeneration is one of the most effective measures, and cadmium sulfide (CdS) materials are typically used as low-cost photocatalysts. The CdS photocatalysts, however, still suffer from low regeneration efficiency and poor cycle stability. In this work, the CdS quantum dots (QDs) less than 10 nm embedded onto silica gel (CdS QDs/Silica gel) were constructed for visible-light-driven NADH regeneration by a successive ionic layer adsorption reaction and ball milling method. Results demonstrate that the photosensitivity of the CdS QDs/Silica gel composite was 31 times higher than that of the bulk CdS. Moreover, the conduction band (CB) edge of the CdS QDs/Silica gel composite is −1.34 eV, which is more negative 0.5 eV than that of the bulk CdS. The obtained CdS QDs/Silica gel composites showed the highest NADH regeneration yields of 68.8% under visible-light (LED, 420 nm) illumination and can be reused for over 40 cycles. Finally, the bioactivity of NADH toward enzyme catalysis is further confirmed by the hydrogenation of benzaldehyde to benzyl alcohol catalyzed with an alcohol dehydrogenase as enzyme catalysis.

View all citing articles on Scopus

Wenjuan Hu is now a graduate student at the Prof. Jian Liu's group at Qingdao University of Science and Technology. She received the B.S. degree (2017) in Metallic Materials Engineering at Qingdao Binhai University. Her research focuses on the photocatalytic cofactor regeneration.

Lijun Yang received her Ph.D. in the Department of Pharmaceutical Science and Technology of Tianjin University (2018) with the major research on synthesis and application of sulfur-containing fluorescent probes. She is now a postdoc in Prof. Jian Liu's group at Qingdao University of Science and Technology. Her research focuses on the synthesis and application of metal-sulfur clusters, metal-organic frameworks (MOFs).

Jian Liu is a professor at Qingdao University of Science and Technology. He received the B.S. degree from Shandong University in 2006 and obtained his PhD degree in 2011 in Prof. Yanlin Song and Prof. Lei Jiang's group from Institute of Chemistry, Chinese Academy of Sciences. He did his first postdoc training with Prof. Markus Antonietti at Max Planck Institute of Colloids and Interfaces as Alexander von Humboldt Fellow and then the second postdoc in Prof. Mercouri G. Kanatzidis's group at Northwestern University. He joined QUST at June of 2017. His research interests focus on bioinspired nanocatalysis for energy conversion.

¹: These authors contributed equally to this work.

View full text

Single cobalt atom anchored on carbon nitride with well-defined active sites for photo-enzyme catalysis

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Catalysts preparation and structural characterization

Conclusion

Chemicals and materials

Synthesis of [Cp*Rh(bpy)H2O]2+

CRediT authorship contribution statement

Declaration of competing interest

Acknowledgements

Chem. Sci.

Nano Energy

Nano Energy

Chem

Appl. Catal., B

Acc. Chem. Res.

Nat. Chem.

Adv. Mater.

Science

J. Am. Chem. Soc.

Angew. Chem. Int. Ed.

Nat. Commun.

J. Am. Chem. Soc.

ACS Catal.

Angew. Chem. Int. Ed.

ACS Catal.

Angew. Chem. Int. Ed.

Synthesis of [Cp*Rh(bpy)H₂O]²⁺