German Edition: DOI: 10.1002/ange.201702213PhotocatalysisInternational Edition: DOI: 10.1002/anie.201702213

Synthesis of Layered Carbonitrides from Biotic Molecules forPhotoredox TransformationsCan Yang, Bo Wang, Linzhu Zhang, Ling Yin, and Xinchen Wang*

Abstract: The construction of layered covalent carbon nitridepolymers based on tri-s-triazine units has been achieved byusing nucleobases (adenine, guanine, cytosine, thymine anduracil) and urea to establish a two-dimensional semiconduct-ing structure that allows band-gap engineering applications.This biomolecule-derived binary carbon nitride polymerenables the generation of energized charge carrier with light-irradiation to induce photoredox reactions for stable hydrogenproduction and heterogeneous organosynthesis of C@O, C@C,C@N and N@N bonds, which may enrich discussion onchemical reactions in prebiotic conditions by taking accountof the photoredox function of conjugated carbonitride semi-conductors that have long been considered to be stable HCN-derived organic macromolecules in space.

Conjugated polymers both in their neutral and chargedstates have gained great attention due to their promisingapplications in electronic devices, such as light-emittingdiodes, lasers, photovoltaic cells, field-effect transistors, andbiology.[1–6] More recently, the applications have experiencedan extension to photoredox catalysis by acting as flexible lighttransducers to enable the construction of soft photosyntheticmachinery/device by using easy solution and thermal pro-cesses.[7–10] Current interest in the emerging field of organicphotocatalysis has focused on the molecular design andmodification of conjugated semiconductors, such as graphiticcarbon nitrides (g-CN) and covalent organic frameworks withspatially extended p-bonding systems.[11–13] Being a stablephotocatalyst with a two-dimensional conjugated structureand reduced exciton-binding energy,[14] g-CN has shown greatpromise for water splitting,[15] CO2 reduction,

[16] and organo-synthesis,[17,18] which has triggered much research devoted toorganic photocatalysis for energy and environmental appli-cations.

Many synthetic strategies, including molten-saltgrowth[19–21] templating[22] and (solvo)thermal condensation[23]

syntheses, have been applied to obtain g-CN nanostructureswith high performance. In particular, thermal condensation isa facile and widely adopted approach to drive the construc-tion and connection of triazine and heptazine tectons to poly-conjugated systems, mostly using nitrogen-containing com-

pounds such as cyanamide, dicyanamide, triazine and hepta-zine derivatives. Further modifications on the chemical andphysical properties by doping and extending its electrondelocalization were achieved by using aromatic precursorscontaining heteroatoms, including B, S, N and P. For example,efficient g-CN photocatalysts have been prepared by thepolymerization of dicyandiamide with 2-aminobenzonitrile or2,4-diaminoquinazoline,[12] and the condensation of urea withbarbituric acid, 2-aminothiophene-3-carbonitrile or diamino-maleonitrile.[14] Considering the diverse array of organicprecursors with different chemical compositions and elec-tronic structures, it practically allows the one-pot design ofpolymer photocatalysts on a molecular level in a rationalmanner, but also enables band-gap engineering, donor/acceptor design, topological fabrication and modifications oftheir physical properties such as p/n characteristics.[24]

In contract to ordinary organic precursors, here we moveone step forward by applying biotic compounds to constructg-CN semiconductors using nucleobases and urea, to answerthe question if g-CN can be produced from lifeQs molecules(Scheme 1).[25] All these compounds are existent in biotic

conditions as lifeQs building blocks from simple precursors inthe primordial soup.[26, 27] We are therefore interested andencouraged to enrich the studies on prebiotic (photo)chem-istry, where HCN polymeric clusters (including triazine-basedsuper carbonitride tectons) have been considered as the mostreadily formed and most stable organic macromolecules inspace.[28] The utilization of these biological precursors for thechemical synthesis of g-CN-based semiconductors by ther-mally induced condensation is representative of the extremeterrestrial and thalassic thermal/hydrothermal conditions ofprimordial Earth; for example the temperatures in hydro-

[*] C. Yang, B. Wang, L. Zhang, L. Yin, Prof. X. WangState Key Laboratory of Photocatalysis on Energy and Environment,College of Chemistry, Fuzhou UniversityFuzhou 350002 (China)E-mail: xcwang@fzu.edu.cnHomepage: http://wanglab.fzu.edu.cn

Supporting information for this article can be found under https://doi.org/10.1002/anie.201702213.

Scheme 1. The chemical production of polymeric carbon nitride semi-conductors from nucleobases and urea.

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http://dx.doi.org/10.1002/ange.201702213http://dx.doi.org/10.1002/anie.201702213https://doi.org/10.1002/anie.201702213https://doi.org/10.1002/anie.201702213

thermal vents close to the volcanic edifices have been foundto range from about 60 88C to 500 88C. The potential existence ofphotoactive g-CN semiconductors in primordial environ-ments to induce photoredox transformations of water, CO2and organics would enrich the discussion on the chemicalevolution of life. Furthermore, the study is also of relevancefor the artificial photosynthesis field.

Nucleobases [adenine (A), guanine (G), cytosine (C),thymine (T) and uracil (U)] are readily available and stableprecursors. Surprisingly, according to our knowledge, there isno report on the synthesis of carbon nitride from biomass-derived building blocks. Here, we propose a facile synthesis ofcarbon nitride based materials by thermal condensation of1) urea with 2) A, G, C, T and U, respectively. We aim todemonstrate that the incorporation of such building blockscan lead to the development of carbon nitride for H2production, and potentially to induce photoredox transfor-mations under prebiotic conditions.

In a typical synthesis, a certain amount of nucleobase (0, 5,15, 30, 50, 80 mg) and urea (10 g) were dissolved in water withstirring, followed by heating at 80 88C to evaporate water.Afterwards, the obtained mixture was calcined at 400–550 88Cin air. The obtained samples are denoted as CNX, where Xrepresents the nucleobase. The reference sample from urea isdenoted as g-CN.

The chemical structure and composition of CNX sampleswere characterized by X-ray diffraction (XRD) (Figure S2a inthe Supporting Information) and Fourier transform infraredspectroscopy (FT-IR) (Figures S2b and S3). The XRDpatterns of the samples in Figure S2a show a strong peak at27.488 related to the (002) interlayer reflection of a layeredcrystal, plus a weak reflection at1388 due to the in-plane repeatingunit of heptazine. The FT-IR spec-trum in Figure S2b features distinctpeaks from 1200 to 1600 cm@1 cor-responding to the stretch modes ofaromatic CN heterocycles, whilethe breathing mode of the triazineunits corresponds to 810 cm@1. Thebroad peaks between 3500 and3100 cm@1 originate from N@Hstretches on the surface of thecarbon nitride due to the surfacedefective sites as a result of incom-plete condensation. These resultsclearly confirmed that all of theCNX materials are featuring sim-ilar crystal and chemical structureof graphitic carbon nitride.

Then, we investigated the pho-tocatalytic activities of CNX sam-ples in water splitting and revealedthe effect of different nucleobasemonomers on the photocatalyticperformances. As shown in Fig-ure S4, the hydrogen evolutionrates (HER) of CNX materialsincrease by 6–8 times as compared

to urea-derived g-CN under visible light irradiation. More-over, the photocatalyst synthesized from urea with cytosine(CNC) exhibits the best activity for producing hydrogenamong all these samples. The superior photocatalytic perfor-mance of CNC is probably due to the better interaction andstructural matching between cytosine and urea. Since onecytosine molecule could break into two molecules with thesimilar structure to urea under thermal treatment, thechemical structure of cytosine enables closer combinationwith urea and better conjugation into the covalent carbonnitride frameworks. On the contrary, the polymerization ofurea with other nucleobases with more functional groups isless straightforward due to steric hindrance. Therefore,cytosine, which could polymerize with the urea best, wasselected as the monomer to synthesize modified carbonnitride polymers with high efficiency for photocatalyticreactions.

A series of photocatalysts were prepared from mixtures ofurea and different amounts of cytosine. These materials aredenoted as CNCy, where y stands for the amount of cytosine(y mg). As shown in Figure 1b and Figure S3 the XRDpattern and FT-IR spectrum of CNCy, respectively, are verysimilar to those of urea-derived g-CN, which demonstratesthat the graphitic carbon nitride based structure is maintainedwith increasing amount of cytosine. The surface morphologyand texture of the CNC30 sample (after Pt deposition) wereinvestigated by scanning electron microscopy (SEM) andtransmission electron microscopy (TEM) (Figure 1a). In theTEM image smooth, flat layers can be seen, and the Ptparticles were distributed uniformly on the surface afterreaction (Figure 1a). There was no obvious difference

Figure 1. a) TEM of Pt@CNC30 after reaction. Inset: HR-TEM of Pt nanoparticles. b) XRD patterns ofdifferent CNC samples. c) XPS analysis of CNC30 sample. d) Solid-state

13C NMR spectrum of CNC30.

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between the morphologies of thesample before and after reaction.During the process of photo-reduc-tion, the Pt nanoparticles were dis-persed on the surface of g-C3N4, andthe size distribution of Pt NPsranged from 3 to 5 nm (Figure 1a,inset), the lattice distance of Pt NPsis 2.28 c.

The solid-state 13C NMR spec-tra of CNC30 (Figure 1d) shows twopeaks, the first peak at 164.3 ppm isascribed to the C(e) atoms [CN2-(NHx)], whereas the second one at155.6 ppm is attributed to the C(i)atoms of melem (CN3). These sig-nals confirm the existence of poly(-tri-s-triazine) structure in CNC30. Inthe XPS survey spectrum (Fig-ure 1c and S5 b–d), there are threeelements (C, N and O), similar tothose of g-CN. The O1s peak pres-ent in CNC30 is due to the surface-absorbed H2O or CO2, as cross-checked by the FT-IR analysis(Figure 1). By increasing the reso-lution of XPS analysis, we observedtwo main carbon species in the C1sspectrum (Figure S5). One carbonspecies with a binding energy (BE)of 287.9 eV is identified as sp2-bound carbon (C@C=C), theother with BE of 284.6 eV was due to carbon impurities. TheN1s XPS spectrum can be deconvoluted into four peaks at398.4, 399.6, 400.8, and 404.2 eV. The strongest N1s peak at398.4 eV was assigned to sp2-bound N in N-containingaromatic rings (C@N=C), whereas the weak peak at399.6 eV is attributed to the tertiary nitrogen N-(C)3 groups.The peak at 400.7 eV indicated the presence of amino groups(C@N@H) and the peak at 404.2 eV was attributed to chargingeffects or positive charge localization in heterocycles.

Figure 2a displays the UV/Vis diffuse reflectance spectra(DRS) of the sample. The optical absorption is red-shiftedfrom 460 nm for g-CN to 470 nm for CNC30 and finally to480 nm for CNC80, corresponding to the change of samplecolor from pale yellow to deep yellow and to orange. Thesechanges are attributed to the combination of cytosinemonomer in the CN that effectively broadens the conjugatedp-electron system and thus narrows the semiconductor bandgap, which is also reflected by PL analysis (Figure 2b)showing gradually red-shift of the emission peaks withincreasing amount of cytosine added. The effect of cytosineaddition on the band structure (valence band and conductionband level) is shown in Figure S6.

With gradual integration of cytosine into the CN network,electron paramagnetic resonance (EPR) intensity increasesprogressively, due to a well-evolved electronic structure withextended delocalization of the p-conjugated system (Fig-ure S7). As expected, the generation of photochemical radicalpairs can be efficiently promoted by this extended p-

conjugated system (see Figure 2c dashed dot line), thusresulting in an enhanced EPR signal in dark condition. Whenthe samples were irradiated with visible light, the signal couldbe enhanced further (Figure 2c, solid lines).

The (photo)electrochemical properties of the CNC30sample was examined by electrochemical impedance spec-troscopy (EIS) and photocurrent test. A marked decrease ofNyquist plots diameter for CNC30 is observed in Figure 2d,which demonstrated that the electronic resistance of CNC30 issmaller compared to pristine g-CN. At the same time, thephotocurrent of CNC30 increased by a factor of four comparedto g-CN (Figure 2 d inset). This photocurrent enhancementillustrates that the mobility of the photo-excited chargecarriers is promoted.

The samples were evaluated in a photocatalytic hydrogenevolution assay by loading 3 wt.% Pt as co-catalyst and usingtriethanolamine (TEOA) as a hole scavenger. Figure 3 ashows that all CNC samples exhibit better catalytic activityin hydrogen evolution than the pure g-CN. Notably, theCNC30 sample shows the highest activity for hydrogenproduction. With increasing amount (from 5 mg to 30 mg)of cytosine in the CNC samples, HER becomes graduallyfaster. The activity decreased when further increasing theamount of cytosine to 80 mg (60 mmol h@1), but is still higherthan with pure g-CN (37 mmolh@1). With 30 mg cytosin anoptimum HER (282 mmolh@1) is achieved, which is nearly 8times faster than with pure g-CN.

The photocatalytic performance of CNC30 is well consis-tent with its optical absorption (Figure 3b), and the amount of

Figure 2. a) UV/Vis DRS spectra. Inset: photograph of the samples. b) Photoluminescence spectraunder 400 nm excitation. c) EPR spectra of CNC30 in the dark (dashed) or with visible light (solid), g-CN as a reference. d) EIS Nyquist plots. Inset: photocurrent of g-CN and CNC30, on/off photocurrentresponse at @0.2 V bias potential vs. Ag/AgCl in 0.2m Na2SO4 solution.

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H2 increased linearly with time under different wavelengths(Figure 3b, inset), suggesting that the main driving force ofthe photocatalytic reaction is the harvested visible photons.

The stability of CNC30 was examined by operating theexperiments under the same reaction conditions for severalruns (Figure S8). Except for the first run, the reaction wastreated without light for one hour to ensure there was no H2gas in the reaction system. A slight deactivation was noticedin the first four runs. When an appropriate amount of TEOAwas added to the reaction solution, the activity of H2evolution improved in the fifth run. This indicates that thedecrease in activity after the first run is mainly due to thedecreased concentration of TEOA. It is noted that no obviousstructural changes were observed (Figure S9–S10).

Next, the apparent quantum yield (AQY) of the bestsample was examined by studying catalytic kinetics usingdifferent amount of photocalalysts. Figure S11 shows thatAQY initially increases with increasing amounts of CNC30,then reaches a plateau at a maximum value of 7.1% beforedecreasing slightly upon further increasing the amount ofcatalyst. We therefore applied 75–100 mg sample to check theintrinsic AQY where the reaction is limited by chargeseparation at the interface to rule out mass diffusion effects.

We further studied the photocatalytic activity of CNC30 inCO2 reduction (Figure S12–S13), using Co(bpy)3Cl2 as redoxmediator and TEOA as electron donor under visible light (l>420 nm). CNC30 photocatalyzed the generation of CO

(32.3 mmol) and H2 (8.02 mmol), with a selectivity for COproduction of 80.1% (entry 1 in Table S1). CNC30 gives thehighest yield and selectivity for CO production, and there isno detectable production of CO in the absence of eitherCNC30 or light (entries 2 and 3 in Table S1). The evolution ofCO was not observed when CO2 was replaced with Ar gas(entry 6 in Table S1), which together with the isotopic experi-ments (Figure S14) confirmed that the source of CO is CO2and not organic sources present in the system.

Besides H2O and CO2, the process of photochemicalevolution involves a series of organic reactions. We thereforechecked the potential capability of the synthetic g-CN inphotocatalyzing the redox transformation of organic mole-cules, including amines, alcohols and the coupling of C@C, C@O, C@N and N@N bonds (Table 1). As shown in entry 1,

amines can be photooxidized into imines by g-CN underoxygen atmosphere, which are regarded as important electro-philic intermediates in organic synthesis. The conversion is79% and the selectivity 98 %. Activation of sp3 C@H bondscan also be achieved, for instance, in entry 2, the CH2 groupwas oxygenated to C=O selectively. The C@O bond in benzylalcohol could be oxidized to C=O (entry 3). In addition, asshown in entries 4 and 5, the synthesized g-CN is also anactive photocatalyst for the coupling of aromatic halides andthe cross-linking of ketone and alcohol. Of particular note,the reactions in entries 4 and 5 are both anaerobic reactionsunder light-irradiation, suggesting a link to the evolution ofalgae for photosynthesis. All reactions mentioned aboveproceed with excellent selectivity and yield, which proves thatheterogeneous photocatalysis offers a promising route torealize green organic syntheses under solar irradiation inambient conditions.

In conclusion, we have demonstrated a biotic precursorapproach to manipulate the texture, surface and opticalproperties of g-CNX polymers synthesized from urea andnucleobases. By optimizing the synthetic recipe, hydrogenevolution reaction under visible light (l> 420 nm) reached

Figure 3. Photocatalytic hydrogen evolution activity of the samples.a) The effect of cytosine amount on HER. b) Wavelength dependenceof the HER with CNC30 loaded with 3 wt. % Pt. Inset: time-dependenceof the HER with CNC30 at different irradiation wavelengths.

Table 1: Different organic reactions driven by the CNC30 photocatalyst.

Entry Reaction Conv. [%] Sel. [%]

1[a] 79 98

2[b] 19.8 96.5

3[c] 56 94

4[d] 99.3 98

5[e] 61.4 90

Reaction conditions: [a] Substrate (1 mmol), catalyst (50 mg), CH3CN(10 mL) as solvent, 80 88C, O2 (1 MPa). [b] Substrate (1 mmol), catalyst(50 mg), CH3CN (4 mL) as solvent, 160 88C, O2 (1 MPa), 24 h. [c] Sub-strate (0.1 mmol), catalyst (5 mg), trifluorotoluene (1.5 mL) as solvent,60 88C, O2 (1 MPa), 3 h under visible light irradiation. [d] Iodobenzene(0.15 mmol) and benzeneboronic acid (0.6 mmol), catalyst (10 mg with3 wt.% Pd), 2.5 mL of water and 2.5 mL of ethanol, K2CO3 (1 mmol),30 88C, 2 h under visible light irradiation. [e] 30 Vol. % substrate aqueoussolution, catalyst (100 mg), 1 wt.% Pt, 24 h under UV/vis lightillumination. All products were detected by GC-MS.

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282 mmolh@1 with an apparent quantum yield of 7.1%, whichis 8-fold higher than with g-CN produced from urea alone.This polymeric catalysts are promising for water splitting, bycoupling with other semiconductors and deposition of anappropriate co-catalyst. The diversity of biomass moleculesand the flexibility of bottom-up synthesis will enable therational development of efficient polymeric light-harvestingtransducers, which could potentially have emerged in natureby thermal assembly of lifeQs building blocks from simplecompounds. This work may enrich the discussion on chemicalreactions under prebiotic conditions by considering a role ofnaturally occurring carbonitride semiconductors. This studycould also extend g-CN photocatalysis to redox transforma-tions of organic molecules including amines, alcohols and thecoupling of C@C, C@O, C@N and N@N bonds.

Acknowledgements

This work was financially supported by the National BasicResearch Program of China (2013CB632405), the NationalNatural Science Foundation of China (21425309 and21761132002) and the 111 Project.

Conflict of interest

The authors declare no conflict of interest.

Keywords: carbon nitride semiconductors · chemical evolution ·nucleobases · photocatalysis · urea

How to cite: Angew. Chem. Int. Ed. 2017, 56, 6627–6631Angew. Chem. 2017, 129, 6727–6731

[1] A. G. Slater, A. I. Cooper, Science 2015, 348, aaa8075.[2] Y. Xu, S. Jin, H. Xu, A. Nagai, D. Jiang, Chem. Soc. Rev. 2013, 42,

8012 – 8031.[3] Y. Wang, X. C. Wang, M. Antonietti, Angew. Chem. Int. Ed.

2012, 51, 68 – 89; Angew. Chem. 2012, 124, 70 – 92.[4] P. Bujak, I. Kulszewicz-Bajer, M. Zagorska, V. Maurel, I.

Wielgus, A. Pron, Chem. Soc. Rev. 2013, 42, 8895 – 8999.[5] C. Duan, K. Zhang, C. Zhong, F. Huang, Y. Cao, Chem. Soc. Rev.

2013, 42, 9071 – 9104.[6] G. G. Zhang, Z. A. Lan, X. C. Wang, Angew. Chem. Int. Ed.

2016, 55, 15712 – 15727; Angew. Chem. 2016, 128, 15940 – 15956.[7] J.-S. Wu, S.-W. Cheng, Y.-J. Cheng, C.-S. Hsu, Chem. Soc. Rev.

2015, 44, 1113 – 1154.

[8] X. Liu, Y. Xu, D. Jiang, J. Am. Chem. Soc. 2012, 134, 8738 – 8741.[9] X. Wu, H. Li, B. Xu, H. Tong, L. Wang, Polym. Chem. 2014, 5,

4521 – 4525.[10] Y. Xu, L. Chen, Z. Guo, A. Nagai, D. Jiang, J. Am. Chem. Soc.

2011, 133, 17622 – 17625.[11] R. S. Sprick, J.-X. Jiang, B. Bonillo, S. Ren, T. Ratvijitvech, P.

Guiglion, M. A. Zwijnenburg, D. J. Adams, A. I. Cooper, J. Am.Chem. Soc. 2015, 137, 3265 – 3270.

[12] J. S. Zhang, G. G. Zhang, X. F. Chen, S. Lin, L. Mohlmann, G.Dolega, G. Lipner, M. Antonietti, S. Blechert, X. C. Wang,Angew. Chem. Int. Ed. 2012, 51, 3183 – 3187; Angew. Chem. 2012,124, 3237 – 3241.

[13] Z. Z. Lin, X. C. Wang, Angew. Chem. Int. Ed. 2013, 52, 1735 –1738; Angew. Chem. 2013, 125, 1779 – 1782.

[14] M. W. Zhang, X. C. Wang, Energy Environ. Sci. 2014, 7, 1902 –1906.

[15] X. C. Wang, K. Maeda, A. Thomas, K. Takanabe, G. Xin, J. M.Carlsson, K. Domen, M. Antonietti, Nat. Mater. 2009, 8, 76 – 80.

[16] J. L. Lin, Z. M. Pan, X. C. Wang, ACS Sustainable Chem. Eng.2014, 2, 353 – 358.

[17] F. Z. Su, S. C. Mathew, G. Lipner, X. Z. Fu, M. Antonietti, S.Blechert, X. C. Wang, J. Am. Chem. Soc. 2010, 132, 16299 –16301.

[18] X.-H. Li, M. Baar, S. Blechert, M. Antonietti, Sci. Rep. 2013, 3,1743.

[19] M. J. Bojdys, J. O. Mgller, M. Antonietti, A. Thomas, Chem. Eur.J. 2008, 14, 8177 – 8182.

[20] K. Schwinghammer, M. B. Mesch, V. Duppel, C. Ziegler, J. R.Senker, B. V. Lotsch, J. Am. Chem. Soc. 2014, 136, 1730 – 1733.

[21] G. Algara-Siller, N. Severin, S. Y. Chong, T. Bjçrkman, R. G.Palgrave, A. Laybourn, M. Antonietti, Y. Z. Khimyak, A. V.Krasheninnikov, J. P. Rabe, Angew. Chem. Int. Ed. 2014, 53,7450 – 7455; Angew. Chem. 2014, 126, 7580 – 7585.

[22] Y. Zheng, L. H. Lin, B. Wang, X. C. Wang, Angew. Chem. Int.Ed. 2015, 54, 12868 – 12884; Angew. Chem. 2015, 127, 13060 –13077.

[23] Y. J. Cui, Z. X. Ding, X. Z. Fu, X. C. Wang, Angew. Chem. Int.Ed. 2012, 51, 11814 – 11818; Angew. Chem. 2012, 124, 11984 –11988.

[24] G. Liu, P. Niu, L. Yin, H.-M. Cheng, J. Am. Chem. Soc. 2012, 134,9070 – 9073.

[25] J. Orl, Biochem. Biophys. Res. Commun. 1960, 2, 407 – 412.[26] P. J. Bracher, Nat. Chem. 2015, 7, 273 – 274.[27] M. W. Powner, B. Gerland, J. D. Sutherland, Nature 2009, 459,

239 – 242.[28] C. N. Matthews, Planet. Space Sci. 1995, 43, 1365 – 1370.

Manuscript received: March 1, 2017Revised manuscript received: March 27, 2017Version of record online: May 4, 2017

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https://doi.org/10.1126/science.aaa8075https://doi.org/10.1039/c3cs60160ahttps://doi.org/10.1039/c3cs60160ahttps://doi.org/10.1002/anie.201101182https://doi.org/10.1002/anie.201101182https://doi.org/10.1002/ange.201101182https://doi.org/10.1039/c3cs60257ehttps://doi.org/10.1039/c3cs60200ahttps://doi.org/10.1039/c3cs60200ahttps://doi.org/10.1002/anie.201607375https://doi.org/10.1002/anie.201607375https://doi.org/10.1002/ange.201607375https://doi.org/10.1039/C4CS00250Dhttps://doi.org/10.1039/C4CS00250Dhttps://doi.org/10.1021/ja303448rhttps://doi.org/10.1039/c4py00305ehttps://doi.org/10.1039/c4py00305ehttps://doi.org/10.1021/ja208284thttps://doi.org/10.1021/ja208284thttps://doi.org/10.1021/ja511552khttps://doi.org/10.1021/ja511552khttps://doi.org/10.1002/anie.201106656https://doi.org/10.1002/ange.201106656https://doi.org/10.1002/ange.201106656https://doi.org/10.1002/anie.201209017https://doi.org/10.1002/anie.201209017https://doi.org/10.1002/ange.201209017https://doi.org/10.1039/c3ee44189jhttps://doi.org/10.1039/c3ee44189jhttps://doi.org/10.1038/nmat2317https://doi.org/10.1021/sc4004295https://doi.org/10.1021/sc4004295https://doi.org/10.1021/ja102866phttps://doi.org/10.1021/ja102866phttps://doi.org/10.1002/chem.200800190https://doi.org/10.1002/chem.200800190https://doi.org/10.1021/ja411321shttps://doi.org/10.1002/anie.201402191https://doi.org/10.1002/anie.201402191https://doi.org/10.1002/ange.201402191https://doi.org/10.1002/anie.201501788https://doi.org/10.1002/anie.201501788https://doi.org/10.1002/ange.201501788https://doi.org/10.1002/ange.201501788https://doi.org/10.1002/anie.201206534https://doi.org/10.1002/anie.201206534https://doi.org/10.1002/ange.201206534https://doi.org/10.1002/ange.201206534https://doi.org/10.1021/ja302897bhttps://doi.org/10.1021/ja302897bhttps://doi.org/10.1016/0006-291X(60)90138-8https://doi.org/10.1038/nchem.2219https://doi.org/10.1038/nature08013https://doi.org/10.1038/nature08013https://doi.org/10.1016/0032-0633(95)00023-Xhttp://www.angewandte.org

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