Toward abiotic sugar synthesis from CO2 electrolysis

Abstract

•A roadmap of CO2 upcycling modules leading to abiotic sugar generation was established•CO2 electroconversion to formaldehyde and glycolaldehyde was experimentally assessed•Glycolaldehyde from CO2 initiated sugar formation in a chemically complex medium•Sugars initiated by CO2-derived glycolaldehyde served as feedstock for Escherichia coli The conversion of CO2 to drop-in and complex products would be transformative to the field of CO2 upcycling. However, limited progress has been achieved using heterogeneous catalysts due to the complexity of favoring one out of the many possible reaction pathways and associated high energy penalties. Here, we establish a pathway toward the generation of a complex product in sugars from CO2 by sequentially combining existing CO2 conversion modules. Initial CO2 products in glycolaldehyde and formaldehyde react together through the formose reaction to generate sugars. We experimentally evaluated commonly reported electrochemical platforms for formaldehyde and glycolaldehyde production from CO2. As a result, we determined that glycolaldehyde even in low quantities is a necessary initiator for sugar formation. Sugars could be an important feedstock in biomanufacturing; therefore, we demonstrated that sugars formed with CO2-derived glycolaldehyde could be used as feedstock. Although steady progress has been achieved toward upcycling waste CO2 through diverse catalytic strategies, each approach has distinct limitations, hampering the generation of complex products like sugars. Here, we provide a roadmap that evaluates the feasibility associated with state-of-the-art electrochemical processes eligible for converting CO2 into glycolaldehydes and formaldehydes, both essential components for sugar generation through the formose reaction. We establish that even in low concentrations, glycolaldehyde plays a crucial role as an autocatalytic initiator during sugar formation and identify formaldehyde production as a bottleneck. Our study demonstrates the chemical resilience of the formose reaction successfully carried out in the chemically complex CO2 electrolysis product stream. This work reveals that CO2-initiated sugars constitute an adequate feedstock for fast-growing and genetically modifiable Escherichia coli. Altogether, we introduce a roadmap, supported by experimental evidence, that pushes the boundaries of product complexity achievable from CO2 electroconversion while integrating CO2 into life-sustaining sugars. Although steady progress has been achieved toward upcycling waste CO2 through diverse catalytic strategies, each approach has distinct limitations, hampering the generation of complex products like sugars. Here, we provide a roadmap that evaluates the feasibility associated with state-of-the-art electrochemical processes eligible for converting CO2 into glycolaldehydes and formaldehydes, both essential components for sugar generation through the formose reaction. We establish that even in low concentrations, glycolaldehyde plays a crucial role as an autocatalytic initiator during sugar formation and identify formaldehyde production as a bottleneck. Our study demonstrates the chemical resilience of the formose reaction successfully carried out in the chemically complex CO2 electrolysis product stream. This work reveals that CO2-initiated sugars constitute an adequate feedstock for fast-growing and genetically modifiable Escherichia coli. Altogether, we introduce a roadmap, supported by experimental evidence, that pushes the boundaries of product complexity achievable from CO2 electroconversion while integrating CO2 into life-sustaining sugars. 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Herein, we point to avenues for potential improvement in electrochemical formaldehyde production to promote higher interest in this valuable product by the CO2 electrochemistry community. Unlike glycolaldehyde, there are various well-established electro- and thermochemical approaches to generate formaldehyde from CO2 (Figure 1; Table 1). For this reason, we employed commercially available formaldehyde as a stand-in and focused on studying the feasibility of coupling heterogeneous electrocatalysis with the formose reaction. Our study demonstrates for the first time the chemical resilience of the formose reaction which was achieved in a chemically complex environment. We establish the feasibility of employing glycolaldehyde, a minority molecule derived from CO2 electroreduction, that is necessary initiator of the autocatalytic pathway of the formose reaction. Specifically, without CO2-derived glycolaldehyde as an autocatalytic initiator, the formose reaction did not yield sugars. Finally, we devised a simple method to prepare the CO2-initiated formose sugars for use as feedstock in an E. coli culture. The E. coli culture proliferated when fed with formose sugars, representing one of the first demonstrations of using abiotically formed sugars to successfully sustain life. Altogether, we showcase a synthetic route to incorporate CO2 electrolysis products into the production of life-sustaining sugars while pointing out the understudied areas necessary to address before fulfilling a complete abiotic CO2-to-sugar conversion.Table 1Detailed summary of the paths toward sugar precursors as illustrated in Figure 1ConversionProcessCatalystConditionsEfficiency/ selectivityProduction rateReference(1) CO2 → formaldehydethermochemicalaDenotes a nascent conversion process with few or singular supporting reports.PtCu/SiO2150°C, 6 atmN/A∼52.2 × 10−4 mol gcat−1 h−1Lee et al.40Lee D.-K. Kim D.-S. Kim S.-W. Selective formation of formaldehyde from carbon dioxide and hydrogen over PtCu/SiO2.Appl. Organomet. Chem. 2001; 15: 148-150Crossref Scopus (21) Google Scholar(1) CO2 → formaldehydeelectrochemicalaDenotes a nascent conversion process with few or singular supporting reports.boron-doped diamond− 1.5 V versus Ag/AgClFE: ∼62%3.75 × 10−4 mol h−1Nakata et al.39Nakata K. Ozaki T. Terashima C. Fujishima A. Einaga Y. High-yield electrochemical production of formaldehyde from CO2 and seawater.Angew. Chem. Int. Ed. Engl. 2014; 53: 871-874Crossref PubMed Scopus (267) Google Scholar(2) CO2 → COthermochemicalbIndicates a well-established or industrially validated catalytic process.Pd/CeO2/Al2O3250°C, 1 barPS: 87%1.62 × 10−4 mol gcat−1 h−1Daza and Kuhn41Daza Y.A. Kuhn J.N. CO2 conversion by reverse water gas shift catalysis: comparison of catalysts, mechanisms and their consequences for CO2 conversion to liquid fuels.RSC Adv. 2016; 6: 49675-49691Crossref Google Scholar(2) CO2 → COthermochemicalbIndicates a well-established or industrially validated catalytic process.La0.75Sr0.25FeO3550°C, 1 barPS: 95%0.13 mol gcat−1 h−1Daza and Kuhn41Daza Y.A. Kuhn J.N. CO2 conversion by reverse water gas shift catalysis: comparison of catalysts, mechanisms and their consequences for CO2 conversion to liquid fuels.RSC Adv. 2016; 6: 49675-49691Crossref Google Scholar(2) CO2 → COelectrochemicalbIndicates a well-established or industrially validated catalytic process.Ag NPsEcell = 2.5 V (GDE)FE: 99%EE: 53%7.8 × 10−3 mol cm−2 h−1Bhargava et al.42Bhargava S.S. Proietto F. Azmoodeh D. Cofell E.R. Henckel D.A. Verma S. Brooks C.J. Gewirth A.A. Kenis P.J.A. System design rules for intensifying the electrochemical reduction of CO2 to CO on Ag nanoparticles.ChemElectroChem. 2020; 7: 2001-2011Crossref Scopus (56) Google Scholar(3) CO → formaldehydethermochemicalaDenotes a nascent conversion process with few or singular supporting reports.Ru-Ni/Al2O380°C, 100 bar, aqueousPS: ∼100%63.2 × 10−6 mol L−1 gcat−1 h−1Bahmanpour et al.43Bahmanpour A.M. Hoadley A. Tanksale A. Formaldehyde production via hydrogenation of carbon monoxide in the aqueous phase.Green Chem. 2015; 17: 3500-3507Crossref Google Scholar(3) CO → formaldehydeelectrochemicalaDenotes a nascent conversion process with few or singular supporting reports.MoP∼20°C, H UPD (−30 mV versus RHE)FE: ∼96%1.8 × 10−4 mol gcat−1 h−1Yao et al.44Yao L. Pan Y. Shen X. Wu D. Bentalib A. Peng Z. Utilizing hydrogen underpotential deposition in CO reduction for highly selective formaldehyde production under ambient conditions.Green Chem. 2020; 22: 5639-5647Crossref Google Scholar(4) CO → CH3OHthermochemicalbIndicates a well-established or industrially validated catalytic process.Cu/ZnO/Al2O3∼240°C, with H2 co-feedN/A2.5 kg L−1 h−1Herman et al.45Herman R.G. Klier K. Simmons G.W. Finn B.P. Bulko J.B. Kobylinski T.P. Catalytic synthesis of methanol from COH2: I. Phase composition, electronic properties, and activities of the Cu/ZnO/M2O3 catalysts.J. Cat. 1979; 56: 407-429Crossref Scopus (585) Google Scholar(4) CO → CH3OHelectrochemicalaDenotes a nascent conversion process with few or singular supporting reports.CoPc−0.64 V versus RHEFE: ∼14%6.3 × 10−6 mol cm−2 h−1Boutin et al.46Boutin E. Wang M. Lin J.C. Mesnage M. Mendoza D. Lassalle-Kaiser B. Hahn C. Jaramillo T.F. Robert M. Aqueous electrochemical reduction of carbon dioxide and carbon monoxide into methanol with cobalt phthalocyanine.Angew. Chem. Int. Ed. Engl. 2019; 58: 16172-16176Crossref PubMed Scopus (91) Google Scholar(5) CO2 → CH3OHthermochemicalbIndicates a well-established or industrially validated catalytic process.Cu/ZnO/AlOOH250°C, 50 atm with H2 co-feed56 C-mol % selectivity, 14.1% yield10.9 mmol gcat−1 h−1Choi et al.47Choi E.G. Song K.H. An S.R. Lee K.Y. Youn M.H. Park K.T. Jeong S.K. Kim H.J. Cu/ZnO/AlOOH catalyst for methanol synthesis through CO2 hydrogenation.Korean J. Chem. Eng. 2018; 35: 73-81Crossref Scopus (29) Google Scholar(5) CO2 → CH3OHelectrochemicalaDenotes a nascent conversion process with few or singular supporting reports.Cu2−xSe NPs−2.1 V versus Ag/Ag+ ACN/H2OFE: ∼78%2 × 10−4 mol cm−2 h−1Yang et al.48Yang D. Zhu Q. Chen C. Liu H. Liu Z. Zhao Z. Zhang X. Liu S. Han B. Selective electroreduction of carbon dioxide to methanol on copper selenide nanocatalysts.Nat. Commun. 2019; 10: 677Crossref PubMed Scopus (185) Google Scholar(6) CH3OH→ formaldehydethermochemicalbIndicates a well-established or industrially validated catalytic process.Ag crystals (ballast)600°C –700°C, 1 atmPS: 87%N/ASperber49Sperber H. Herstellung von formaldehyd aus methanol in der BASF.Chemie Ing. Techn. 1969; 41: 962-966Crossref Scopus (43) Google Scholar(6) CH3OH → formaldehydethermochemicalbIndicates a well-established or industrially validated catalytic process.Fe2(MoO4)3 (Formox)250°C –400°C, 1 atmPS: ∼99%N/ABahmanpour et al.50Bahmanpour A.M. Hoadley A. Tanksale A. Critical review and exergy analysis of formaldehyde production processes.Rev. Chem. Eng. 2014; 30: 583-604Crossref Scopus (59) Google Scholar(6) CH3OH → formaldehydeelectrochemicalaDenotes a nascent conversion process with few or singular supporting reports.Pt (polycrystalline, disc)0.25 V versus Ag/AgCl (0.1 M HClO4)FE: ∼38%1.8 × 10−8 mol cm−2 h−1Korzeniewski and Childers51Korzeniewski C. Childers C.L. Formaldehyde yields from methanol electrochemical oxidation on platinum.J. Phys. Chem. B. 1998; 102: 489-492Crossref Scopus (97) Google Scholar(7) CO2 → glycolaldehydeelectrochemicalbIndicates a well-established or industrially validated catalytic process.Cu NPs−0.81 V versus RHE (0.1 M KHCO3)FE: ∼0.2%N/AKim et al.35Kim D. Kley C.S. Li Y. Yang P. Copper nanoparticle ensembles for selective electroreduction of CO2 to C2–C3 products.Proc. Natl. Acad. Sci. USA. 2017; 114: 10560-10565Crossref PubMed Scopus (348) Google ScholarThe number in parenthesis is associated with the conversion step in Figure 1. For each module, reported operating conditions are shown along with productions rate and product selectivity. NPs, nanoparticles; FE, faradaic efficiency; PS, process selectivity; EE, energy efficiency; RHE, reversible hydrogen electrode; H UPD, hydrogen underpotential deposition; GDE, gas diffusion electrode; ACN, acetonitrile.a Denotes a nascent conversion process with few or singular supporting reports.b Indicates a well-established or industrially validated catalytic process. Open table in a new tab The number in parenthesis is associated with the conversion step in Figure 1. For each module, reported operating conditions are shown along with productions rate and product selectivity. NPs, nanoparticles; FE, faradaic efficiency; PS, process selectivity; EE, energy efficiency; RHE, reversible hydrogen electrode; H UPD, hydrogen underpotential deposition; GDE, gas diffusion electrode; ACN, acetonitrile. Abiotic sugar synthesis from CO2 could provide an avenue for drop-in chemical, material, fuel, and even food production.7García Martínez J.B. Alvarado K.A. Christodoulou X. Denkenberger D.C. 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