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1. Electron and Spin Delocalization in [Co ₆ Se ₈ (PEt ₃ ) ₆ ] ^0/+1 Superatoms

   https://doi.org/10.1002/cphc.202300064  

   Xu, Yunyao; Chen, Jia; Aydt, Alexander P.; Zhang, Lichirui; Sergeyev, Ivan; Keeler, Eric G.; Choi, Bonnie; He, Shoushou; Reichman, David R.; Friesner, Richard A.; et al (January 2024, ChemPhysChem)

   ChemPhysChem (Ed.)

   Abstract Molecular clusters can function as nanoscale atoms/superatoms, assembling into superatomic solids, a new class of solid‐state materials with designable properties through modifications on superatoms. To explore possibilities on diversifying building blocks, here we thoroughly studied one representative superatom, Co₆Se₈(PEt₃)₆. We probed its structural, electronic, and magnetic properties and revealed its detailed electronic structure as valence electrons delocalize over inorganic [Co₆Se₈] core while ligands function as an insulated shell.⁵⁹Co SSNMR measurements on the core and³¹P,¹³C on the ligands show that the neutral Co₆Se₈(PEt₃)₆is diamagnetic and symmetric, with all ligands magnetically equivalent. Quantum computations cross‐validate NMR results and reveal degenerate delocalized HOMO orbitals, indicating aromaticity. Ligand substitution keeps the inorganic core nearly intact. After losing one electron, the unpaired electron in [Co₆Se₈(PEt₃)₆]⁺¹is delocalized, causing paramagnetism and a delocalized electron spin. Notably, this feature of electron/spin delocalization over a large cluster is attractive for special single‐electron devices. 

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2. What is the fate of xylem‐transported CO ₂ in Kranz‐type C ₄ plants?

   https://doi.org/10.1111/nph.15908  

   Stutz, Samantha S.; Hanson, David T. (June 2019, New Phytologist)

   Summary High concentrations of dissolved inorganic carbon in stems of herbaceous and woody C₃plants exit leaves in the dark. In the light, C₃species use a small portion of xylem‐transported CO₂for leaf photosynthesis. However, it is not known if xylem‐transported CO₂will exit leaves in the dark or be used for photosynthesis in the light in Kranz‐type C₄plants.Cut leaves ofAmaranthus hypochondriacuswere placed in one of three solutions of [NaH¹³CO₃] dissolved in KCl water to measure the efflux of xylem‐transported CO₂exiting the leaf in the dark or rates of assimilation of xylem‐transported CO₂* in the light, in real‐time, using a tunable diode laser absorption spectroscope.In the dark, the efflux of xylem‐transported CO₂increased with increasing rates of transpiration and [¹³CO₂*]; however, rates of¹³C_effluxinA. hypochondriacuswere lower compared to C₃species. In the light,A. hypochondriacusfixed nearly 75% of the xylem‐transported CO₂supplied to the leaf.Kranz anatomy and biochemistry likely influence the efflux of xylem‐transported CO₂out of cut leaves ofA. hypochondriacusin the dark, as well as the use of xylem‐transported CO₂* for photosynthesis in the light. Thus increasing the carbon use efficiency of Kranz‐type C₄species over C₃species. 

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3. Using Phosphonic Acid Monolayers to Control CO ₂ Adsorption and Hydrogenation on Pt/Al ₂ O ₃

   https://doi.org/10.1002/cctc.202400451  

   Blanchette, Zachary; Zhou, Xinpei; Schwartz, Daniel_K; Medlin, J_Will (August 2024, ChemCatChem)

   Abstract Phosphonic acid (PA) self‐assembled monolayers (SAMs) were deposited onto Pt/Al₂O₃catalysts to modify the support to enable control over CO₂adsorption and CO₂hydrogenation activity. Significant differences in catalytic activity toward CO₂hydrogenation (reverse water‐gas shift, RWGS) were observed after coating Al₂O₃with PAs, suggesting that the reaction was mediated by CO₂adsorption on the support. Amine‐functionalized PAs were found to outperform their alkyl counterparts in terms of activity, however there was little effect of amine location in the SAM (i. e., spacing between the amine functional group and phosphonate attachment group). One amine‐PA and one alkyl‐PA, aminopropyl phosphonic acid (C₃NH₂PA) and methyl phosphonic acid (C₁PA), respectively, were investigated in more detail. The C₃NH₂PA‐modified catalyst was found to bind CO₂as a combination of carbamate and bicarbonate. Additionally, at 30 °C, both PAs were found to reduce CO₂adsorption uptake by approximately 50 % compared to unmodified 5 %Pt/Al₂O₃. CO₂adsorption enthalpy was measured for the catalysts and found to be strongly correlated with hydrogenation activity, with the trend in binding enthalpy and CO₂hydrogen rate trending as uncoated >C₃NH₂PA>C₁PA. PA SAMs were found to have weaker effects on CO binding and CO selectivity, consistent with selective modification of the Al₂O₃support by the PAs. 

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4. Contribution and consequences of xylem‐transported CO ₂ assimilation for C ₃ plants

   https://doi.org/10.1111/nph.15907  

   Stutz, Samantha S.; Hanson, David T. (June 2019, New Phytologist)

   Summary Traditionally, leaves were thought to be supplied withCO₂for photosynthesis by the atmosphere and respiration. Recent studies, however, have shown that the xylem also transports a significant amount of inorganic carbon into leaves through the bulk flow of water. However, little is known about the dynamics and proportion of xylem‐transportedCO₂that is assimilated, vs simply lost to transpiration.Cut leaves ofPopulus deltoidesandBrassica napuswere placed in eitherKCl or one of three [NaH¹³CO₃] solutions dissolved in water to simultaneously measure the assimilation and the efflux of xylem‐transportedCO₂exiting the leaf across light andCO₂response curves in real‐time using a tunable diode laser absorption spectroscope.The rates of assimilation and efflux of xylem‐transportedCO₂increased with increasing xylem [¹³CO₂*] and transpiration. Under saturating irradiance, rates of assimilation using xylem‐transportedCO₂accounted forc.2.5% of the total assimilation in both species in the highest [¹³CO₂*].The majority of xylem‐transportedCO₂is assimilated, and efflux is small compared to respiration. Assimilation of xylem‐transportedCO₂comprises a small portion of total photosynthesis, but may be more important whenCO₂is limiting. 

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5. CO ₂ Capture and Direct Air CO ₂ Capture Followed by Integrated Conversion to Methane Assisted by Metal Hydroxides and a Ru/Al ₂ O ₃ Catalyst

   https://doi.org/10.1002/cctc.202300877  

   Koch, Christopher_J; Suhail, Zohaib; Goeppert, Alain; Prakash, G_K_Surya (October 2023, ChemCatChem)

   Abstract Rising CO₂levels are leading to an increase in atmospheric greenhouse gas effect. Hydroxide salts have previously been shown to be promising reagents for capturing CO₂. Utilizing a 5 %Ru/Al₂O₃catalyst, the carbonates obtained through CO₂capture can then be hydrogenated to methane. This conversion occurs at relatively mild temperatures from 200 °C to 250 °C under 40 to 70 bar H₂with yields of up to 100 %. Natural sources of calcium carbonate, like eggshells and seashells, can also be partially converted to methane. The direct air CO₂capture and conversion of CO₂to methane was achieved as well in quantitative yields. 

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