Methanol-to-olefins (MTO) is a prevalent industrial process for producing light olefins from the non-petroleum route. Molecular sieves are core catalysts for MTO owing to their unique pore structure and tunable acidity. Solid-state nuclear magnetic resonance (NMR) is a powerful tool to elucidate the structure and interpret the catalytic reaction mechanism of the molecular sieves. In this review, we summarize the major progresses in understanding the MTO reaction mechanism with in-situ solid-state NMR, multi-dimensional and -nuclear NMR, ¹²⁹Xe NMR, and pulsed field gradient NMR (PFG NMR). In-situ solid-state NMR can monitor the dynamic changes of the reactants, intermediates and products under real reaction conditions. Multi-dimensional and multi-nuclear NMR offers rich structural information of the reaction intermediate without having to destroy the catalyst structure. Especially, ¹²⁹Xe NMR is applied to sensitively probe the pore structure of fresh and deactivated catalysts. PFG NMR could determine the diffusion coefficients of molecules in pores, and elucidate the diffusion mechanism of the molecular sieve.

Two-dimensional J-resolved (2D J_RES) nuclear magnetic resonance (NMR) experiments provide a simple and user-friendly spectral representation, in which J couplings and chemical shifts are separated into two orthogonal frequency dimensions. The 2D J_RES experiments have attracted wide attention in fundamental pulse sequence developments and practical applications, since they were first proposed 40 years ago. In this paper, we review the recent advances in the development of novel 2D J_RES pulse sequences and 2D J-edited methods for accurate measurements of J coupling, mainly focusing on pure shift based 2D orthogonal-pattern and phase-sensitive 2D J_RES spectroscopy and their applications in overcoming strong coupling effects and field inhomogeneities.

Solid acid is one of the most widely applied heterogeneous catalysts for industrial hydrocarbon conversion and biomass refining. It is crucial to understand the nature of solid acid such as its local structure and acidic properties. Such knowledge renders effective design of solid acid with better activity and stability for the desired reaction. Recently, solid-state nuclear magnetic resonance (SSNMR) spectroscopy has been applied as a powerful standard method for characterizing the local structure and acidic nature of solid acid in both qualitative and quantitative manners. Additionally, the applications of advanced two-dimensional SSNMR methodologies further reveal the symmetry of surface sites, spatial relationship of different sites, and thereby unmasking the structure-activity relationship. In this review, we summarize the general methods and SSNMR techniques for the routine characterization, focusing on the progresses in the understanding of local structure and acidic properties of solid acids via the application of SSNMR with or without probe molecules.

Molecular imaging plays an increasingly important role in the early diagnosis and detection of tumors. As a significant branch of molecular imaging, magnetic resonance imaging (MRI) shows incomparable advantages and broad development prospects than other imaging technologies. It requires no radioactive tracer, no ionizing radiation, but presents high spatial and temporal resolution and tissue contrast. In recent years, a series of progress has been made in the research and development of new magnetic resonance molecular probes and imaging sequences, including responsive molecular probes, ¹⁹F MRI, hyperpolarized ¹²⁹Xe MRI, and chemical exchange saturation transfer (CEST) imaging, which have expanded the application range of MRI. One crucial research in MRI development is to further improve sensitivity. Therefore, the research of new multimodal MRI contrast agents with good targeting capacity, high relaxation efficiency and high safety is an important topic in the current biomedical engineering field. For example, the sensitivity of MRI molecular probes could be improved by combining the characteristics of micelles with some new magnetic resonance methods. Some deficiencies of MRI could be overcome by introducing multimodal molecular probes. This article reviews the research progress and application analysis of the core technology of micellar MRI molecular probes, and elucidates the importance of molecular imaging technology in biomedical engineering research and clinical diagnosis.

Solid-state nuclear magnetic resonance (NMR) is an important technique to study the acidity and basicity of solid catalysts. Here we review some research works carried out in our laboratory, including studies on the acidity of metal oxides under different water contents, the acidity and basicity characterization of metal oxides by using acidic and basic probe molecules simultaneously. The investigations extend solid-state NMR technique in qualitative and quantitative studies on the acidity and basicity of solid catalysts.

MYC is a highly expressed oncogene in about 70% of human cancer cells and inhibition of its transcription serves as an effective tumor treatment. The P1 proximal nuclease hypersensitive element (NHE) Ⅲ₁ of c-MYC promoter region controls nearly 90% transcriptional activation of MYC gene. This region enriched with base G forms G-quadruplex (G4) structure, which regulates c-MYC gene transcription and is a target of anti-tumor drugs. However, the three-dimensional structures of G4-DNA and G4-RNA are highly similar. Non-specific interactions between small molecules and other G4s, such as telomere G4, mRNA G4, c-Kit G4, etc., yield "off-target" effects. Meanwhile, small molecules can induce the formation of other G4s, thus interfering with the function of normal cells. All of these hinder the design of anti-cancer drugs targeting c-MYC G4. In this paper, we summarize the recent research progress of small molecules targeting tumor factor c-MYC G4-DNA, and the role of nuclear magnetic resonance (NMR) in determining G4-DNA and G4-RNA structure. This review provides a reference for designing drugs targeting c-MYC G4-DNA and other related research works.

In this study, solid-state nuclear magnetic resonance (NMR) spectroscopy was used to probe the changes of acidity of H-ZSM-5 zeolite caused by ammonium hexafluorosilicate (AHFS) washing-related changes of aluminium species. It was observed that the four-coordinate framework aluminum species with Brønsted acidity were partially reduced, while the tri-coordinated framework aluminum with Lewis acidity was slightly decreased after the AHFS treatment. However, AHFS washing was also found to induce mild dealumination and a significant reduction of aluminum species with Lewis acidity containing Al-OH group on zeolites, thus resulting in a remarkable change in the overall acidity of the zeolites.

Nuclear magnetic resonance (NMR) is a major method used to study protein structure at atomic resolution. Besides presenting the high-resolution structure, NMR facilitates studies on protein dynamics near physiological conditions that are intimately related to the biological mechanism of the proteins. Unnatural amino acids (UAA) labeling could significantly reduce the complexity of protein NMR spectra. In this review, we briefly summarize the widely used UAA labeling strategies for proteins, including chemical peptide synthesis, residue-specific peptide modification, ¹⁹F labeled aromatic amino acids incorporation and genetic code expansion based UAA incorporation. The recent applicants of UAA in characterizing protein structure and dynamics, the limitations and prospects of UAA are also highlighted.

Many applications of oxide nanomaterials depend on their surface structure and properties. Solid-state nuclear magnetic resonance (NMR) spectroscopy has been used to obtain such key information in related studies. This paper summarizes two recently developed approaches based on solid-state NMR spectroscopy for determining the surface structure and properties of oxide nanomaterials, including surface-selective isotopic labeling ¹⁷O NMR and dynamic nuclear polarization surface enhanced NMR spectroscopy. The development trend for investigating oxide nanomaterials with solid-state NMR spectroscopy is also introduced.

The catalytic performance of zeolite SSZ-39 with AEI structure is significantly affected by the locations of its extra-framework cation and aluminum distributions. The AEI cage contains three crystallographically inequivalent T sites that tend to be substituted by aluminum. In this work, the Na⁺ locations and Al distributions in Na-SSZ-39 with different Si/Al ratios were studied by ²⁷Al/²³Na MQ MAS NMR spectroscopy together with density functional theory (DFT) calculations. For isolated Al substitution, the T3 site was found to be preferentially occupied by Al, and Na⁺ was mainly located in the 6-MR (SIIa0) or 8-MR (SIII'a0) sites of the AEI cage, although the priority of SIII'a0 site was slightly higher, and minor Na⁺ was located inside the hexagonal prism (SIa0). For paired Al substitution, stable AlSiSiAl structure was found to be located in 6-MR, and the corresponding Na⁺ cations were located at SIIa1 and SIII'a1 sites, respectively. In post-modified zeolites with partial destruction of the framework structure, some free Na⁺ cations were found to form distinct SIII'b sites. This study deepened the understanding on the structure-reactivity correlation of SSZ-39 zeolite and provided insights into how to fine-tune its catalytic performance.

Brønsted acid sites (BASs) on amorphous silica-aluminas (ASAs) are key active sites that can be generated based on tetra-coordinated aluminum (Al^IV) species, albeit much weaker than that of zeolites. Penta-coordinated aluminum (Al^V) species are recently reported to enhance the acidity of ASAs, and to overcome the limitations of Al^IV species. This review introduces novel strategies to control the synthesis of Al^V-enriched ASAs using flame spray pyrolysis (FSP) techniques. The acidic properties and local structure of Al^V-enriched ASAs were characterized by various advanced 2D solid-state nuclear magnetic resonance (SSNMR) techniques and in situ ¹H MAS NMR experiments, showing two new types of BASs from moderate to zeolitic acid strength based on Al^V species. ²⁷Al and ¹H MAS NMR studies uncovered the role of Al^V species in tailoring single-atom catalysts on ASAs.

Due to their excellent catalytic performances in the conversion of biomass molecules such as glucose and lactic acid, the Sn-containing zeolite catalysts have received wide attention. Understanding detailed structures and acidity properties of the active sites and the corresponding catalytic reaction mechanisms is a critical step in developing fundamental insights into the catalytic function and exploiting more highly active zeolite catalysts. Solid-state nuclear magnetic resonance (NMR) spectroscopy provides useful information on the local structures and acidity properties of active centers, as well as the catalytic reaction mechanisms in zeolites. This review briefly introduces the application of solid-state NMR technique in the studies on Sn-containing zeolites. Further challenges and perspectives are also discussed.