13C CPMAS NMR Research Articles

Ionothermal synthesis and characterisation of Mn-, Co-, Fe- and Ni-containing aluminophosphates

Metalloaluminophosphates (MAPOs) containing different metal ions (Mn3+, Mn2+, Co2+, Fe2+ or Ni2+) were synthesised in ionic liquids to investigate the effect of changing ionic liquid structure, reaction time, the nature of metal ions, and the initial metal/Al as well as F/Al ratios. A combination of XRD, 13C CP MAS NMR, SEM images, Volhard titration, UV-Vis, thermogravimetric and nitrogen sorption measurements were performed to characterise the resulting MAPOs. The AFI framework of manganese-containing aluminophosphate (MnAPO) was prepared in an efficient way using MnF3 in 1-butyl-3-methylimidazolium bromide ([C4mim]Br) as both solvent and structure-directing agent (SDA). It was found that the resulting framework type can be altered by changing the ionic liquid's structure (cation, anion or alkyl chain) and this also influences the manganese content in the framework. Furthermore, tetramethylammonium fluoride ([Me4N]F) was employed as both mineraliser and co-SDA in the presences of [C4mim]Br for the formation of Mn-, Fe-, Co- and NiAPOs. The resulting framework type is dependent on the amounts of [Me4N]F and the nature of metal precursor, and as a result, the LTA, the SOD or a mixture of two framework types was obtained. The extent of substitution of metal atoms is directly dependent on the initial [Me4N]F/Al ratio, and metal cation (Fe2+ > Ni2+ > Co2+ > Mn2+) employed. The presented study leads to the first description for the ionothermal synthesis of MnAPO (CHA or LTA) and NiAPO (LTA), and offers efficient synthesis compared to previously reported ionothermal or hydrothermal methods.

Substrate dependence on the fixation of CO2 to cyclic carbonates over reusable porous hybrid solids

N,N,N-tributyl-N-propylammonium iodide-functionalized mesoporous silicas (SBA-15 and a silica gel) proved to be efficient, robust and reusable catalysts for the solvent-free synthesis of cyclic carbonates (CCs) from epoxides and CO2. The reusability of the catalysts was found to be dependent on the nature of the support and the substrate. In the presence of 1,2-epoxybutane (1,2-EB) as substrate, the SBA-15-based catalyst (PHS-1) exhibited a constant catalytic activity for five reaction cycles (yield > 96.0%) under mild conditions (1.0 MPa CO2, 100 °C and 4 h). Conversely, in the presence of styrene oxide, a gradual decrease in yield was observed. Based on textural properties and 13C CP-MAS NMR measurements, such decline was attributed to the adsorption of solid reaction product (styrene carbonate - SC) on the catalyst surface. Using a chromatographic silica gel as support and an improved catalyst recovery step gave rise to a highly efficient, robust and fully reusable catalyst (PHS-2) for the synthesis of CCs. Notably, PHS-2 led to a 33–50% decrease in reaction time, and maintained an excellent and steady catalytic activity over 5 cycles in the synthesis of SC (yield > 96% and selectivity > 97%). The amount of trapped solid SC product on PHS-2 surface was also significantly reduced.

Applications of Nanomaterials Based on Magnetite and Mesoporous Silica on the Selective Detection of Zinc Ion in Live Cell Imaging.

Functionalized magnetite nanoparticles (FMNPs) and functionalized mesoporous silica nanoparticles (FMSNs) were synthesized by the conjugation of magnetite and mesoporous silica with the small and fluorogenic benzothiazole ligand, that is, 2(2-hydroxyphenyl)benzothiazole (hpbtz). The synthesized fluorescent nanoparticles were characterized by FTIR, XRD, XRF, 13C CP MAS NMR, BET, and TEM. The photophysical behavior of FMNPs and FMSNs in ethanol was studied using fluorescence spectroscopy. The modification of magnetite and silica scaffolds with the highly fluorescent benzothiazole ligand enabled the nanoparticles to be used as selective and sensitive optical probes for zinc ion detection. Moreover, the presence of hpbtz in FMNPs and FMSNs induced efficient cell viability and zinc ion uptake, with desirable signaling in the normal human kidney epithelial (Hek293) cell line. The significant viability of FMNPs and FMSNs (80% and 92%, respectively) indicates a potential applicability of these nanoparticles as in vitro imaging agents. The calculated limit of detections (LODs) were found to be 2.53 × 10−6 and 2.55 × 10−6 M for Fe3O4-H@hpbtz and MSN-Et3N-IPTMS-hpbtz-f1, respectively. FMSNs showed more pronounced zinc signaling relative to FMNPs, as a result of the more efficient penetration into the cells.

Photocatalytic hydrogen evolution from formate and aldehyde over molecular iridium complexes stabilized by bipyridine-bridging organosilica nanotubes

An efficient heterogeneous photocatalytic system for high-purity hydrogen evolution from formate or aldehyde-water solution were developed using IrCp*Cl (Cp* = η5-pentamethylcyclopentadienyl) complex anchored onto the robust bipyridine-based organosilica nanotubes as a solid catalyst. This system can be conducted at the room temperature with a visible light (λ > 420 nm) illumination. The heterogeneous molecular photocatalyst displayed much improved catalytic activity and recyclability compared to the analogous homogeneous catalyst, benefiting from the isolated photoactive sites as well as the efficient transport of substrates and products in the nanotube channels. A detailed characterization for the solid catalyst after the reactions by UV/vis, XPS and 13C CP MAS NMR testified the molecular nature of the active species. This work provides an easy method to construct the heterogeneous molecular photocatalysts for the high-purity hydrogen generation under mild conditions.

Concepts and Misconceptions of Humic Substances as the Stable Part of Soil Organic Matter: A Review

In the last three decades, the concept of soil humic substances has been questioned in two main directions. Misinterpretations of CP MAS13C NMR spectroscopy led to the conclusion that soil organic matter is mainly aliphatic, questioning the theory of polymerization of humic substances from phenolic molecules. Conversely, some critics of humic substances assume that a great proportion of aromatic soil organic carbon originates from fire-affected carbon, often termed as black carbon (BC). However, the determination of BC in soil by two widely applied methods, the benzene polycarboxylic acid marker method and the UV method, is not reliable and seems to strongly overestimate the BC content of soils. The concept of humic substances continues to be relevant today. The polymerization of phenolic molecules that originate from the degradation of lignin or synthesis by microorganisms may lead to humic substances which can incorporate a variety of organic and inorganic molecules and elements. The incorporation, e.g., of triazines or surfactants into the humic matrix, leading to bound residues, illustrates that humic substances are important to explain central reactions in soil. Humic substances are also important to understand the availability of plant nutrients in soil, including P, Fe, and Cu, and they may have a direct effect on the growth of higher plants in soil. Therefore, there are good reasons to reformulate or to further develop the concepts and models of humic substances introduced and developed by M. Schnitzer, W. Flaig, W. Ziechmann, and F.J. Stevenson.

Polybenzimidazole-nanocomposite membranes: Enhanced proton conductivity with low content of amine-functionalized nanoparticles

In this work, a pyridine based polybenzimidazole (PPBI) is synthesized (I.V. 3.3 dL/g) from pyridine dicarboxylic acid and hydrochloride salt of diaminobenzidine. The polymer is characterized by FTIR and 13C CP-MAS NMR. The resultant PPBI possesses high storage modulus of >10 GPa, tensile modulus of ∼1 GPa and tensile strength of ∼150 MPa. Amine functionalized silica nanoparticles in different degrees of amine grafting (LAC-low amine content/HAC-high amine content) are successfully incorporated into PPBI to result nanocomposite membranes. Both the neat PPBI and nanocomposites exhibit significant affinity towards phosphoric acid as indicated by the high acid uptake in short time (5 h). Proton conductivity of nanocomposites is increased by the addition of LAC/HAC nanoparticles (>250 mS/cm at 140 °C). The HAC nanoparticle enriched nanocomposite (HAC 7) reveals self-assembly of amino-silica nanoparticles due to base-base repulsion (imidazole-amine). Hydrophobicity of nanocomposite membranes is increased with increase in LAC/HAC content which is attributed to the strengthening of hydrogen bonding between PPBI and nanoparticles.

Faster N Release, but Not C Loss, From Leaf Litter of Invasives Compared to Native Species in Mediterranean Ecosystems.

Plant invasions can have relevant impacts on biogeochemical cycles, whose extent, in Mediterranean ecosystems, have not yet been systematically assessed comparing litter carbon (C) and nitrogen (N) dynamics between invasive plants and native communities. We carried out a 1-year litterbag experiment in 4 different plant communities (grassland, sand dune, riparian and mixed forests) on 8 invasives and 24 autochthonous plant species, used as control. Plant litter was characterized for mass loss, N release, proximate lignin and litter chemistry by 13C CPMAS NMR. Native and invasive species showed significant differences in litter chemical traits, with invaders generally showing higher N concentration and lower lignin/N ratio. Mass loss data revealed no consistent differences between native and invasive species, although some woody and vine invaders showed exceptionally high decomposition rate. In contrast, N release rate from litter was faster for invasive plants compared to native species. N concentration, lignin content and relative abundance of methoxyl and N-alkyl C region from 13C CPMAS NMR spectra were the parameters that better explained mass loss and N mineralization rates. Our findings demonstrate that during litter decomposition invasive species litter has no different decomposition rates but greater N release rate compared to natives. Accordingly, invasives are expected to affect N cycle in Mediterranean plant communities, possibly promoting a shift of plant assemblages.

Cationic Pyridylamido Adsorbate on Brønsted Acidic Sulfated Zirconia: A Molecular Supported Organohafnium Catalyst for Olefin Homo- and Co-Polymerization

Here we report the combined application of high-resolution solid-state 13C–CPMAS-NMR and FT-IR spectroscopy, elemental analysis, kinetic poisoning/active site counting, variable dielectric constant medium, and DFT computation to characterize the surface chemistry of a pyridylamido hafnium complex (Cat1, L1-HfMe2, L1 = 2,6-diisopropyl-N-{(2-isopropylphenyl)[6-(naphthalen-1-yl)pyridin-2-yl]methyl}aniline) adsorbed on Bronsted acidic sulfated zirconia (ZrS). The spectroscopic and DFT results indicate protonolytic formation of organohafnium cations having a largely electrostatic pyridylamido-Hf-CH3+···ZrS– interaction with elongated Hf···OZrS distances of ∼2.14 A. High-molecular-weight polyethylenes and ethylene/1-octene copolymers are obtained with this supported catalyst without an activator/cocatalyst. The DFT calculations reveal that the first ethylene insertion into the Hf-methyl bond has a lower barrier than the corresponding insertion into the Hf-aryl bond of this single-site heterogeneous catalyst.

Highly Ion-Conducting, Reversibly Stretchable, and Ultra-Durable Double-Networked Ionogels for Flexible Supercapacitor

Flexible energy storage devices perform well under normal condition and their performance merits are well understood. However, energy storage under extreme conditions is still a big challenge because of electrolyte degradation and separator instability for the application such as an electrical vehicle, oil, solar energy storage, aerospace and military. Wet gels such as hydro- and organogels are mechanically strong yet brittle. Among functional gels, gel electrolytes are considered to resolve critical challenges of liquid and solid electrolytes, but they also have the property trade-offs between ion transporting and mechanical properties, as well as between strength and toughness. The performance degradation and safety issue of electrolytes prohibit flexible energy storage from operating under mechanically, thermally and electrochemically extreme conditions. Here, we report a new class of solid electrolyte, “Double Crosslinked Ionogel” based on double network concept. The tailor made ionogel electrolyte/separator structure was prepared by synthesizing double network gel from complimentary polymers and by combining it with room temperature ionic liquid. The unique structure of double crosslinked ionogel electrolyte was characterized by solid-state 13C CP-MAS NMR and FT-IR spectroscopies. Dual crosslinked polymer structure provide greater stretchability (strain ~250%) and high mechanical strength (3 MPa) to the electrolyte. At the same time presence of high amount of ionic liquid results (~60 wt%) in enhanced electrochemical performance i.e. Potential window (~2V), Maximum energy density (~40 Wh kg-1) and Ionic conductivity (~1.8 mS cm-1 at Room temp). With rGO electrodes and prepared ionogel electrolyte/separator, the supercapacitor device shows stable performance up to 180°C with good cyclic stability. High temperature promotes faster ion transport and hence results in enhanced performance in terms of rate capability (≈40%) and maximum device capacitance (≈ 32 F g-1). There was very little performance attenuation observed even under extreme mechanical and thermal stress. The device retains around ~90 % of its initial capacitance even after 100000 of cycles at 150 °C and capable of delivering required energy and power at high temperature.

Thermal, Spectroscopic, and Crystallographic Analysis of Mannose-Derived Linear Polyols

The major diastereomer formed in the Barbier-type metal-mediated allylation of d-mannose has previously been shown to adopt a perfectly linear conformation, both in solid state and in solution, resulting in the formation of hydrogen-bonded networks and subsequent aggregation from aqueous solution upon stirring. Here, a comprehensive study of the solid state structure of both the allylated d-mannose and its racemic form has been conducted. The binary melting point diagram of the system was determined by differential scanning calorimetry analysis, and the obtained results, along with structure determination by single crystal X-ray diffraction, confirmed that allylated mannose forms a true racemate. Further examination by powder X-ray diffraction and CP MAS 13C NMR spectroscopy revealed polymorphism both in the pure enantiomer and in the racemate. In addition, the propargylated and hydrogenated analogues of allylated d-mannose were prepared and subjected to thermal and spectroscopic analyses. The crystal structure of the propargylated compound was successfully determined, showing a linear molecular conformation similar to that found for allylated d-mannose. Both new compounds likewise display aggregation behavior in water, further verifying that the low-energy linear conformation plays a significant role in this unusual behavior of these rodlike mannose derivatives.

Isocyanate-Free Polyurethane Coatings and Adhesives from Mono- and Di-Saccharides.

Mostly biosourced non-isocyanate polyurethanes (NIPU) were prepared from mono- and disaccharides, namely glucose and sucrose, reacted with dimethyl carbonate and hexamethylene diamine. The main aim of this research was to show that NIPU can be prepared from mono- and disaccharides, this just being an initial exploratory work and its sole main aim. The oligomers obtained were detected by MALDI-ToF, CP-MAS 13C NMR, and FTIR spectrometries. The glucose-derived NIPU were shown to harden at a markedly lower temperature than the sucrose-derived ones and to be easier to handle and spread. The NIPU obtained were applied as wood and steel surface coatings and tested by the sessile drop test (on wood) and cross-cut test (on steel) with encouraging results. The glucose NIPU gave good surface coating results already at 103 °C, while the sucrose NIPU yielded good results only at a markedly higher temperature of hardening. The NIPU saccharide resins were also tested as thermosetting wood joint adhesives with the glucose NIPU yielding very encouraging results.

Nucleating and Plasticization Effects in Drawn Poly(Lactic Acid) Fiber during Accelerated Weathering Degradation.

Changes in the polymer properties of poly(lactic acid) (PLA) fibers during drawing and degradation processes were analyzed using solid-state NMR, with the goal of elucidating morphological changes that influence fiber tensile properties. Combination of X-ray diffraction (XRD) and differential scanning calorimeter (DSC) indicated that the drawn PLA fibers consisted of different proportions of α crystalline and amorphous forms. 13C CP-MAS NMR spectra showed amorphous-like broad singlet signals, of which the full width at half maximum (FWHM) decreased with increasing crystallinity and crystal orientation. The T1H value decreased by interaction with additives and increased with increasing crystal orientation. The interaction with additives also reduced T1C values, which increased with increasing crystallinity. Use of organic clay enhanced the crystallization of high draw-ratio PLA fibers due to nucleation, which increased tensile strength; this effect gradually decreased with time during accelerated weathering. In contrast, the plasticization due to the addition of flexible polymers increased fiber elongation, which rapidly dropped during the degradation. Changes of FWHM, T1H, and T1C values indicated that the degradation occurred at sites within the amorphous portions of the PLA fibers containing organic clay, while the flexible polymers were preferentially degraded if they were present in the PLA fibers.

Cross‐Linked Polyamine from Imidazolium‐Based Materials: A Simple Route to Useful Catalytic Materials

Cross‐linked polyamine‐based materials were easily prepared by reduction of the corresponding cross‐linked imidazolium‐based materials with sodium borohydride in hot ethanol. Overall, the synthetic procedure is based on the polymerization of a suitable bis‐vinylimidazolium salt with or without a suitable support, such as silica or silica‐coated magnetic nanoparticles (γ‐Fe2O3@SiO2), followed by reduction. This simple approach allows the synthesis of materials based on a network of secondary and tertiary amines. Materials were characterized by 13C cross‐polarization magic angle spinning NMR (13C CPMAS NMR), proton spin‐lattice relaxation times in the rotating frame (T1ρH) and thermogravimetric analysis (TGA). Cross‐linked polyamine‐based materials were used as recoverable catalyst for Knoevenagel reaction. High yields of the condensation products were obtained and up to 11 cycles were carried out.

Linking plant phytochemistry to soil processes and functions: the usefulness of 13C NMR spectroscopy

The organic matter cycle is one of the most fundamental processes in ecosystems affecting the soil and controlling its functions. The soil complex microbiome is made up of thousands of bacterial and hundreds of fungal strains that coexist on the many different available organic carbon sources. In natural plant communities, freshly fallen leaf-litter and dead roots are subject to decomposition by a complex food-web composed of both microbial saprotrophs and invertebrate detritivores. The litter chemical composition varies dramatically among species in relation to plant life forms (conifer, broadleaf, nitrogen-fixing, graminoid) and, within species, with plant organs (leaf, root, woody tissues). This paper reviews the usefulness of advanced chemical technologies to study the composition of both plant litter and organic amendments, supporting the description of their mechanism of action and attention to their potential applications. First, a critical review is presented on the limitations of C/N and lignin/N ratios, still widely used as basic indicators of litter chemistry. Second, the potential of the solid state 13C-CPMAS NMR is reported as a powerful tool to assess the chemical composition of both litter and organic amendments. Finally, six different study cases are reported to provide evidence of the usefulness of such metabolomic approach for the description of organic matter chemistry aimed to an effective prediction of its impact on soil ecosystem functions.

Highly efficient and selective production of acrylic acid from 3-hydroxypropionic acid over acidic heterogeneous catalysts

The process for dehydration of 3-hydroxypropionic acid to produce acrylic acid was investigated over solid acid catalysts containing HY, ZSM-5, Beta, MCM-41 and silica gel. These catalysts were comprehensively characterized by techniques including XRD, nitrogen adsorption–desorption, NH3-TPD, Pyridine-IR, TGA and 13C CP MAS-NMR. Silica gel was found to show the highest acrylic acid selectivity of >99.0% at a complete 3-hydroxypropionic acid conversion. Results from NH3-TPD and Pyridine-IR analyses reveal that the acidity has a significant effect on catalytic performance. The selective conversion of 3-hydroxypropionic acid to acrylic acid over silica gel can be ascribed to the weak and small amount of Lewis acid sites as well as the absence of Brønsted acid sites. Increasing Brønsted acid sites for HY, ZSM-5, Beta and MCM-41 resulted in low acrylic acid selectivities due to increasing of acetic acid formation. TG and 13C CP MAS-NMR results further indicate that the presence of Brønsted acid sites favors the formation of coke. And the coke deposited on these catalysts has a primarily aromatic nature. Stability test indicates the silica gel catalyst exhibits an excellent stability for 200 h.

Effects of organic wastes on structural characterizations of humic acid in semiarid soil under plastic mulched drip irrigation

The objective of this work was to evaluate the variation in the amount and structure of humic acid (HA) after the application of organic wastes (OWs) in semiarid soil under plastic mulched drip irrigation, measured by elemental composition, excitation-emission matrix (EEM) fluorescence, and carbon 13 nuclear magnetic resonance (13C CPMAS NMR). The experiment involved chemical fertilizer combined with chicken manure (CM), sheep manure (SM), maize straw (MS), fodder grass (FG), and tree leaves (TL), while chemical fertilizer only was used as control (CK). The highest cation exchange capacity (CEC), soil organic carbon (SOC), and HA contents (P < 0.05) were achieved for TL compared to other OWs. The E4/E6 ratio, ΔlogK value, and the aliphatic C/aromatic C ratio of HA were the lowest for TL treatment than for other OW treatments, whereas the highest C/H ratio was obtained. The specific fluorescence intensities (SFI) of peak A (330–370/460-490 nm), peak B (450–465/515-525 nm), and peak C (255–270/465-490 nm) mainly referred to humic acid component from EEM fluorescence spectrum of HA were lower for TL compared to other OWs. In conclusion, the application of TL was the most effective for improving the accumulation of SOC and HA, and making the structure of HA complex and stability. Thus, TL is the recommended OW for use in semiarid soil under plastic mulched drip irrigation conditions.

Synthesis of ferrocenylazobenzene-functionalized MCM-41 via direct co-condensation method

Ferrocenylazobenzene-functionalized mesoporous MCM-41 material (Fc-Az-M14), was synthesized directly through co-condensation of 4-triethoxysilyl-3′-ferrocenylazobenzene (TEFA) and tetraethyl orthosilicate (TEOS), under basic conditions, using cetyltrimethylammmonium bromide (CTAB) as structure-directing agent. The template was removed through solvent extraction, to yield the ferrocenylazobenzene-containing ordered mesoporous organosilicas Fc-Az-M41. The prepared material was characterized by nitrogen adsorption, X-ray diffraction (XRD), solid state 29Si MAS NMR and 13C CP-MAS NMR, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Thermogravimetric analysis (TGA) and diffuse reflectance UV-Vis spectroscopy (DR UV). The results showed that Fc-Az-M41 had an ordered two-dimensional hexagonal mesostructure, high BET surface area and pore volume. The pore diameter, BET surface area, and pore volume of the extracted material were 3.8 nm, 1070 m2/g and 0.80 cm3/g, respectively. The mean pore diameters of MCM-41 clearly decreased by ca. 0.65 nm upon incorporation of Fc-Az groups. UV-Vis spectrum of Fc-Az-M41 was determined by a diffuse reflectance method after UV irradiation. The presence of the azobenzene chromophores in this material can be clearly observed in the DR UV-Vis spectra of surfactant-free Fc-Az-M41. This spectra shows that the framework of this material is formed predominantly by trans isomer, and the π-π* and the n-π* absorption bands were affected by metal-to-ligand charge transfer (MLCT).

A novel hybrid of β-cyclodextrin grafted onto activated carbon for rapid adsorption of naphthalene from aqueous solution

A novel hybrid material was prepared by grafting β-cyclodextrin (β-CD) onto the surface of oxidized AC for the rapid adsorption of naphthalene. AC and CDACs were characterized using the N2 adsorption–desorption method, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and solid state CP MAS 13C NMR. All the results demonstrate that β-CD grafted successfully onto AC. Batch experimental adsorption datas had a higher correlation to Freundlich isotherm model and the pseudo-second-order model. The adsorption equilibrium capacity of 178.73mg·g−1 was reached in just 10s at an AC/β-CD grafting ratio value of 1:1. It had a faster adsorption rate than many reported adsorbents. Additionally, the positive free energy change (∆G°), and the positive enthalpy change (∆H°) suggest that it is a viable, spontaneous and endothermic process, which will provided a new path to a highly-efficient and fast-adsorption-rate adsorbent for naphthalene or its analogues discharged into the environment.

Short-term interaction between organic matter from biofuel defatted seed cakes and soil microbiota in two intensive horticulture systems

In the last decades, use of biodiesel, produced by oil seeds, has widely increased. Defatted seed cakes are the most important byproducts of biodiesel production chain and their agricultural valorization is becoming a global challenge. The aim of this study was to characterize carbon molecular composition of several seed cakes (Brassica carinata A. Braun, Brassica napus L. and several components of Helianthus annuus L. seed wastes) by means of 13C CPMAS-NMR spectroscopy and evaluate their short-term effects on soil microbial activities, in two intensive horticulture systems. Defatted seed cakes used in this study have relevant differences in chemical composition and significant conditioning effects on soil microbiota. Seed cakes from sunflower were characterized by a higher content of celluloses, as carbohydrates composition, while Brassicaceae seed cakes were rich in more biochemical stable compounds and secondary metabolites, such as glucosinolates precursors of anti-microbial molecules. These latter ones, along with the larger amount of carbon molecules with an highest biochemical stability, negatively affected microbial growth resulting, generally, in lower soil activities. In conclusion, this study unraveled, for the first time, the molecular carbon composition of several biofuel byproducts and showed how the seed cakes can be evaluate for soil amendments, thus permitting to convert byproducts from biofuel chain to co-products useful in agriculture.

Multi-analysis of chemical transformations of lignin macromolecules from waterlogged archaeological wood

A large number of archaeological wooden building poles have been excavated from the Hai Menkou site (Yunnan province, China). Lignin can be transformed and altered accompanied with significant loss of carbohydrates during this process. Elucidation of chemical and structural transformations of lignin is of primary importance for understanding both the nature of degradation processes and the structure of waterlogged archaeological wood, and crucial for developing proper consolidation technology and restoring artifacts of historical and cultural value. In this study, state-of-the-art analytical techniques, including SEM, FT-IR, XRD, CP-MAS 13C NMR, 2D-HSQC NMR, 31P-NMR, CRM, GPC and TG analysis, were all employed to elucidate the structural characteristics of lignin in waterlogged and reference Pinus wood. The results interpreted by NMR analysis demonstrated the depolymerization of lignin via cleavage of β-O-4, β-5, −OCH3 and some LCC linkages, leading to a higher amount of free phenol OH groups in the lignin from the ancient waterlogged wood as compared to that of the reference wood. Microscopically, it was found that extensive degradation of carbohydrates in cell walls was mainly occurred in secondary cell walls, while the lignin concentrations were relatively increased in CCML and S regions in the plant cell wall of the ancient wood.