Hybrid organic-inorganic two-dimensional metal carbide MXenes with amido- and imido-terminated surfaces

Two-dimensional (2D) transition-metal carbides and nitrides (MXenes) show impressive performance in applications, such as supercapacitors, batteries, electromagnetic interference shielding, or electrocatalysis. These materials combine the electronic and mechanical properties of 2D inorganic crystals with chemically modifiable surfaces, and surface-engineered MXenes represent an ideal platform for fundamental and applied studies of interfaces in 2D functional materials. A natural step in structural engineering of MXene compounds is the development and understanding of MXenes with various organic functional groups covalently bound to inorganic 2D sheets. Such hybrid structures have the potential to unite the tailorability of organic molecules with the unique electronic properties of inorganic 2D solids. Here, we introduce a new family of hybrid MXenes (h-MXenes) with amido- and imido-bonding between organic and inorganic parts. The description of h-MXene structure requires an intricate mix of concepts from the fields of coordination chemistry, self-assembled monolayers (SAMs) and surface science. The optical properties of h-MXenes reveal coherent coupling between the organic and inorganic components. h-MXenes also show superior stability against hydrolysis in aqueous solutions.Comment: 10 pages, 4 figure

A Crosslinked Ionic Organic Framework for Efficient Iodine and Iodide Remediation in Water

Iodine is widely used as an antimicrobial reagent for water disinfection in the wilderness and outer space, but residual iodine and iodide need to be removed for health reasons. Currently, it is challenging to remove low concentrations of iodine and iodide in water (~5 ppm). Furthermore, the remediation of iodine and iodide across a broad temperature range (up to 90 °C) has not previously been investigated. In this work, we report a nitrate dimer-directed synthesis of a single-crystalline ionic hydrogen-bonded crosslinked organic framework (HCOF-7). HCOF-7 removes iodine and iodide species in water efficiently through halogen bonding and anion exchange, reducing the total iodine concentration to 0.22 ppm at room temperature. Packed HCOF-7 columns were employed for iodine/iodide breakthrough experiments between 23 and 90 °C, and large breakthrough volumes were recorded (≥18.3 L/g). The high iodine/iodide removal benchmarks recorded under practical conditions make HCOF-7 a promising adsorbent for water treatment.This is the peer-reviewed version of the following article: Zhang, Mingshi, Jayanta Samanta, Benjamin Atterberry, Richard Staples, Aaron J. Rossini, and Chenfeng Ke. "A Crosslinked Ionic Organic Framework for Efficient Iodine and Iodide Remediation in Water." Angewandte Chemie International Edition (2022). It has been published in final form at DOI: 10.1002/anie.202214189. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. Copyright 2022 Wiley-VCH. Posted with permission. DOE Contract Number(s): AC02-07CH11358; DMR-1844920; 191956

Double Echo Symmetry-Based REDOR and RESPDOR Pulse Sequences for Proton Detected Measurements of Heteronuclear Dipolar Coupling Constants

1H{X} symmetry-based rotational echo double resonance pulse sequences (S-REDOR) and symmetry-based rotational echo saturation pulse double resonance (S-RESPDOR) solid-state NMR experiments have found widespread application for 1H detected measurements of difference NMR spectra, dipolar coupling constants, and internuclear distances under conditions of fast magic angle spinning (MAS). In these experiments the supercycled () symmetry-based recoupling pulse sequence is typically applied to the 1H spins to reintroduce heteronuclear dipolar couplings. However, the timing of , and other symmetry-based pulse sequences must be precisely synchronized with the rotation of the sample, otherwise, the evolution of 1H CSA and other interactions will not be properly refocused. For this reason, significant distortions are often observed in experimental dipolar dephasing difference curves obtained with S-REDOR or S-RESPDOR pulse sequences. Here we introduce a family of double echo (DE) S-REDOR/S-RESPDOR pulse sequences that function in an analogous manner to the recently introduced t1-noise eliminated (TONE) family of dipolar heteronuclear multiple quantum coherence (D-HMQC) pulse sequences. Through numerical simulations and experiments the DE S-REDOR/S-RESPDOR sequences are shown to provide dephasing difference curves similar to those obtained with S-REDOR/S-RESPDOR. However, the DE sequences are more robust to the deviations of the MAS frequency from the ideal value that occurs during typical solid-state NMR experiments. The DE sequences are shown to provide more reliable 1H detected dipolar dephasing difference curves for nuclei such as 15N (with isotopic labelling), 183W and 35Cl. The double echo sequences are therefore recommended to be used in place of conventional REDOR/RESPDOR sequences for measurement of weak dipolar coupling constants and long-range distances.This article is published as Atterberry, Benjamin A., Scott L. Carnahan, Yunhua Chen, Amrit Venkatesh, and Aaron J. Rossini. "Double Echo Symmetry-Based REDOR and RESPDOR Pulse Sequences for Proton Detected Measurements of Heteronuclear Dipolar Coupling Constants." Journal of Magnetic Resonance (2022): 107147. DOI: 10.1016/j.jmr.2022.107147. Copyright 2022 Elsevier Inc. Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0). Posted with permission. DOE Contract Number(s): AC02-07CH11358

Phosphine Ligand Binding and Catalytic Activity of Group 10–14 Heterobimetallic Complexes

Heterobimetallic complexes have attracted much interest due to their broad range of structures and reactivities as well as unique catalytic abilities. Additionally, these complexes can be utilized as single-source precursors for the synthesis of binary intermetallic compounds. An example is the family of bis(pyridine-2-thiolato)dichloro-germanium and tin complexes of group 10 metals (Pd and Pt). The reactivity of these heterobimetallic complexes is highly tunable through substitution of the group 14 element and the neutral ligand bound to the transition metal. Here, we study the binding energies of three different phosphorous-based ligands, PR3 (R = Bu, Ph, and OPh) by density functional theory and restricted Hartree–Fock methods. The PR3 ligand-binding energies follow the trend of PBu3 > PPh3 > P(OPh)3, in agreement with their sigma-bonding ability. These results are confirmed by ligand exchange experiments monitored with 31P NMR spectroscopy, in which a weaker binding PR3 ligand is replaced with a stronger one. Furthermore, we demonstrate that the heterobimetallic complexes are active catalysts in the Negishi coupling reaction, where stronger binding PR3 ligands inhibit access to an active site at the metal center. Similar strategies could be applied to other complexes to better understand their ligand-binding energetics and predict their reactivity as both precursors and catalysts."This is a manuscript of an article published as Daniels, Carena L., Eunbyeol Gi, Benjamin A. Atterberry, Rafael Blome-Fernández, Aaron J. Rossini, and Javier Vela. "Phosphine Ligand Binding and Catalytic Activity of Group 10–14 Heterobimetallic Complexes." Inorganic Chemistry 61, no. 18 (2022): 6888-6897. DOI: 10.1021/acs.inorgchem.2c00229. Copyright 2022 American Chemical Society. Posted with permission. DOE Contract Number(s): AC02-07CH11358

Molecular and Electronic Structure of Isolated Platinum Sites Enabled by the Expedient Measurement of 195 Pt Chemical Shift Anisotropy

International audienceTechniques thatcancharacterize themolecular structures ofdilute surfacespeciesarerequired tofacilitate therationalsynthesis andimprovement of Pt-based heterogeneous catalysts. 195Ptsolid-state NMRspectroscopy couldbean idealtoolforthistaskbecause 195Ptisotropic chemical shiftsandchemical shift anisotropy (CSA)arehighlysensitive probesofthelocalchemical environment andelectronic structure. However, thecharacterization ofPtsurface-sites is complicated bythetypicallowPtloadings thatarebetween 0.2and5wt%and broadening of 195Ptsolid-state NMRspectrabyCSA.Here,weintroduce asetof solid-state NMRmethods thatexploitfastMASandindirectdetection usinga sensitive spynucleus( 1Hor 31P)toenabletherapidacquisition of 195PtMAS NMRspectra.Wedemonstrate thathigh-resolution wideline 195PtMASNMRspectracanbeacquired inminutestoafewhoursfor aseriesofmolecular andsingle-site PtspeciesgraftedonsilicawithPtloadingofonly3-5wt%.Low-power, long-duration, sidebandselective excitation, andsaturation pulsesareincorporated into t1-noiseeliminated dipolarheteronuclear multiple quantum coherence, perfectechoresonance echosaturation pulsedoubleresonance, or J-resolved pulsesequences. Thecomplete 195PtMAS NMRspectrum isthenreconstructed byrecording aseriesof1DNMRspectrawheretheoffsetofthe 195Ptpulsesisvariedin increments oftheMASfrequency. Analysisofthe 195PtMASNMRspectrayieldsthe 195Ptchemical shifttensorparameters. Zeroth orderapproximation densityfunctional theorycalculations accurately predict 195PtCStensorparameters. Simpleandpredictive orbitalmodelsrelatetheCStensorparameters tothePtelectronic structure andcoordination environment. Themethodology developed herepavesthewayforthedetailedstructural andelectronic analysisofdiluteplatinum surface-sites

The Molecular and Electronic Structure of Isolated Platinum Sites Enabled by Expedient Measurement of 195Pt Chemical Shift Anisotropy

Techniques that can characterize the molecular structures of dilute surface species are required to facilitate the rational synthesis and improvement of single-site and single-atom, such as the important class of Pt-based systems. In this context, 195Pt solid-state NMR spectroscopy could be an ideal tool for this task because 195Pt NMR spectra and sizeable chemical shift anisotropy (CSA) are highly sensitive probes of the local chemical environment and electronic structure. However, the broadening of 195Pt solid-state NMR spectra by CSA often results in low NMR sensitivity. Furthermore, characterization of Pt sites on surfaces is complicated by the typical low Pt loadings that are between 0.2 to 5 wt.%. Here, we introduce a set of solid-state NMR methods that exploit fast MAS and indirect detection of a sensitive spy nucleus (1H or 31P) to enable rapid acquisition of 195Pt MAS NMR spectra. We demonstrate that high-resolution wideline 195Pt MAS NMR spectra can be in minutes to a few hours for a series of molecular and single-site Pt species grafted on silica with Pt loading of only 3-5 wt.%. Low-power, long-duration, sideband-selective excitation and saturation pulses are incorporated into t1-noise eliminated (TONE) dipolar heteronuclear multiple quantum coherence (D-HMQC), perfect echo resonance echo saturation pulse double resonance (PE RESPDOR) or J-resolved pulse sequences. The complete 195Pt MAS NMR spectrum is then reconstructed by recording a series of 1D NMR spectra where the offset of the 195Pt pulses is varied. Analysis of the 195Pt MAS NMR spectra yields the 195Pt chemical shift tensor parameters. Analysis of the NMR signatures based on relativistic zeroth order approximation (ZORA) DFT calculations enables the rationalization of changes in the observed 195Pt CSA across the series of Pt compounds. Simple and predictive orbital models relate the measured spectral signatures to specific electronic environments and allows the identification of coordination environment by inspection of the CSA (isotropic chemical shift and measured spans). The methodology developed here paves the way for the detailed structural and electronic analysis of dilute platinum sites in single-atom and single-site heterogeneous catalysts

Accelerated Acquisition of Wideline Solid-State NMR Spectra of Spin 3/2 Nuclei by Frequency-Stepped Indirect Detection Experiments

73% of all NMR-active nuclei are quadrupolar nuclei with a nuclear spin I > 1/2. The broadening of the solid-state NMR signals by the quadrupolar interaction often leads to poor sensitivity and low resolution. In this work we present experimental and theoretical investigations of magic angle spinning (MAS) 1H{X} double-echo resonance-echo saturation-pulse double-resonance (DE-RESPDOR) and Y{X} J-resolved solid-state NMR experiments for the indirect detection of spin 3/2 quadrupolar nuclei (X = spin 3/2 nuclei, Y = spin 1/2 nuclei). In these experiments, the spectrum of the quadrupolar nucleus is reconstructed by plotting the observed dephasing of the detected spin as a function of the transmitter offset of the indirectly detected spin. Numerical simulations were used to investigate the achievable levels of dephasing and to predict the lineshapes of indirectly detected NMR spectra of the quadrupolar nucleus. We demonstrate 1H, 31P and 207Pb detection of 35Cl, 81Br, and 63Cu (I = 3/2) nuclei in trans-Cl2Pt(NH3)2 (transplatin), (CH3NH3)PbCl3 (methylammonium lead chloride, MAPbCl3), (CH3NH3)PbBr3 (methylammonium lead bromide, MAPbBr3) and CH3C(CH2PPh2)3CuI (1,1,1-tris(diphenylphosphinomethyl)ethane copper(I) iodide, triphosCuI), respectively. In all of these experiments, we were able to detect megahertz wide central transition or satellite transition powder patterns. Significant time savings and gains in sensitivity were attained in several test cases. Additionally, the indirect detection experiments provide valuable structural information because they confirm the presence of dipolar or scalar couplings between the detected nucleus and the quadrupolar nucleus of interest. Finally, numerical simulations suggest these methods are also potentially applicable to abundant spin 5/2 and spin 7/2 quadrupolar nuclei.This article is published as Lamahewage, Sujeewa, Benjamin A. Atterberry, Rick Dorn, Eunbyeol Gi, Maxwell R. Kimball, Javier Vela, Janet Bluemel, and Aaron J. Rossini. "Accelerated Acquisition of Wideline Solid-State NMR Spectra of Spin 3/2 Nuclei by Frequency-Stepped Indirect Detection Experiments." Physical Chemistry Chemical Physics (2024). doi: https://doi.org/10.1039/D3CP05055F. This Open Access Article is licensed under a Creative Commons Attribution-NonCommercial 3.0

The Molecular and Electronic Structure of Isolated Platinum Sites Enabled by Expedient Measurement of 195Pt Chemical Shift Anisotropy

Techniques that can characterize the molecular structures of dilute surface species are required to facilitate the rational synthesis and improvement of single-site and single-atom, such as the important class of Pt-based systems. In this context, 195Pt solid-state NMR spectroscopy could be an ideal tool for this task because 195Pt NMR spectra and sizeable chemical shift anisotropy (CSA) are highly sensitive probes of the local chemical environment and electronic structure. However, the broadening of 195Pt solid-state NMR spectra by CSA often results in low NMR sensitivity. Furthermore, characterization of Pt sites on surfaces is complicated by the typical low Pt loadings that are between 0.2 to 5 wt.%. Here, we introduce a set of solid-state NMR methods that exploit fast MAS and indirect detection of a sensitive spy nucleus (1H or 31P) to enable rapid acquisition of 195Pt MAS NMR spectra. We demonstrate that high-resolution wideline 195Pt MAS NMR spectra can be in minutes to a few hours for a series of molecular and single-site Pt species grafted on silica with Pt loading of only 3-5 wt.%. Low-power, long-duration, sideband-selective excitation and saturation pulses are incorporated into t1-noise eliminated (TONE) dipolar heteronuclear multiple quantum coherence (D-HMQC), perfect echo resonance echo saturation pulse double resonance (PE RESPDOR) or J-resolved pulse sequences. The complete 195Pt MAS NMR spectrum is then reconstructed by recording a series of 1D NMR spectra where the offset of the 195Pt pulses is varied. Analysis of the 195Pt MAS NMR spectra yields the 195Pt chemical shift tensor parameters. Analysis of the NMR signatures based on relativistic zeroth order approximation (ZORA) DFT calculations enables the rationalization of changes in the observed 195Pt CSA across the series of Pt compounds. Simple and predictive orbital models relate the measured spectral signatures to specific electronic environments and allows the identification of coordination environment by inspection of the CSA (isotropic chemical shift and measured spans). The methodology developed here paves the way for the detailed structural and electronic analysis of dilute platinum sites in single-atom and single-site heterogeneous catalysts.This is a pre-print of the article Venkatesh, Amrit, Domenico Gioffrè, Benjamin Atterberry, Lukas Rochlitz, Scott Carnahan, Zhuoran Wang, Georges Menzildjian, Anne Lesage, Christophe Coperét, and Aaron Rossini. "The Molecular and Electronic Structure of Isolated Platinum Sites Enabled by Expedient Measurement of 195Pt Chemical Shift Anisotropy." (2022). DOI: 10.26434/chemrxiv-2022-j2f5h. Copyright 2022 The Authors. Attribution-NonCommercial 4.0 International (CC BY-NC 4.0). Posted with permission

Molecular and Electronic Structure of Isolated Platinum Sites Enabled by the Expedient Measurement of 195Pt Chemical Shift Anisotropy

Techniques that can characterize the molecular structures of dilute surface species are required to facilitate the rational synthesis and improvement of Pt-based heterogeneous catalysts. 195Pt solid-state NMR spectroscopy could be an ideal tool for this task because 195Pt isotropic chemical shifts and chemical shift anisotropy (CSA) are highly sensitive probes of the local chemical environment and electronic structure. However, the characterization of Pt surface-sites is complicated by the typical low Pt loadings that are between 0.2 and 5 wt% and broadening of 195Pt solid-state NMR spectra by CSA. Here, we introduce a set of solid-state NMR methods that exploit fast MAS and indirect detection using a sensitive spy nucleus (1H or 31P) to enable the rapid acquisition of 195Pt MAS NMR spectra. We demonstrate that high-resolution wideline 195Pt MAS NMR spectra can be acquired in minutes to a few hours for a series of molecular and single-site Pt species grafted on silica with Pt loading of only 3-5 wt%. Low-power, long-duration, sideband-selective excitation, and saturation pulses are incorporated into t1-noise eliminated dipolar heteronuclear multiple quantum coherence, perfect echo resonance echo saturation pulse double resonance, or J-resolved pulse sequences. The complete 195Pt MAS NMR spectrum is then reconstructed by recording a series of 1D NMR spectra where the offset of the 195Pt pulses is varied in increments of the MAS frequency. Analysis of the 195Pt MAS NMR spectra yields the 195Pt chemical shift tensor parameters. Zeroth order approximation density functional theory calculations accurately predict 195Pt CS tensor parameters. Simple and predictive orbital models relate the CS tensor parameters to the Pt electronic structure and coordination environment. The methodology developed here paves the way for the detailed structural and electronic analysis of dilute platinum surface-sites.ISSN:0002-7863ISSN:1520-512

Hybrid organic-inorganic two-dimensional metal carbide MXenes with amido- and imido-terminated surfaces

Two-dimensional (2D) transition-metal carbides and nitrides (MXenes) show impressive performance in applications, such as supercapacitors, batteries, electromagnetic interference shielding, or electrocatalysis. These materials combine the electronic and mechanical properties of 2D inorganic crystals with chemically modifiable surfaces, and surface-engineered MXenes represent an ideal platform for fundamental and applied studies of interfaces in 2D functional materials. A natural step in structural engineering of MXene compounds is the development and understanding of MXenes with various organic functional groups covalently bound to inorganic 2D sheets. Such hybrid structures have the potential to unite the tailorability of organic molecules with the unique electronic properties of inorganic 2D solids. Here, we introduce a new family of hybrid MXenes (h-MXenes) with amido- and imido-bonding between organic and inorganic parts. The description of h-MXene structure requires an intricate mix of concepts from the fields of coordination chemistry, self-assembled monolayers (SAMs) and surface science. The optical properties of h-MXenes reveal coherent coupling between the organic and inorganic components. h-MXenes also show superior stability against hydrolysis in aqueous solutions.This is a pre-print of the article Zhou, Chenkun, Di Wang, Francisco Lagunas, Benjamin Atterberry, Ming Lei, Huicheng Hu, Zirui Zhou et al. "Hybrid organic-inorganic two-dimensional metal carbide MXenes with amido-and imido-terminated surfaces." arXiv preprint arXiv:2305.17566 (2023). DOI: 10.48550/arXiv.2305.17566, Attribution 4.0 International (CC BY 4.0). Copyright 2023 The Authors. Posted with permission