Publications by authors named "Yanhang Ma"

Photoinduced proton transfer is an essential photochemical process for designing photocatalysts, white light emitters, bioimaging, and fluorescence sensing materials. However, deliberate control of the excited/ground states and meticulous manipulation of the excited state intramolecular proton transfer (ESIPT) pathway constitute a significant challenge in liquids and dense solids. Here, we present the integration of a hydronaphthoquinone fluorophore into a crystalline, porous, phototautomeric dynamic 3D covalent organic framework (COF) to show guest-induced fluorescence turn-on, emission redshift enhancement, and shortened lifetimes for ratiometric fluorescence humidity sensing.

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Boron dipyrromethene (BODIPY)-based zirconium metal-organic frameworks (Zr-MOFs) possess strong light-harvesting capabilities and great potential for artificial photosynthesis without the use of sacrificial reagents. However, their direct preparation has not yet been achieved due to challenges in synthesizing suitable ligands. Herein, we reported the first successful direct synthesis of BODIPY-based Zr-MOFs, utilizing CO as a feedstock.

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Chiral inorganic nanomaterials have attracted broad interest due to their intriguing chirality-dependent performances. However, there is a lack of experimental studies and atomic-level evidence on their growth mechanism. Herein, high-crystalline chiral tellurium nanowires were synthesized in an alkali solution by using tellurium oxide as an inorganic source and hydrazine hydrate as a reductant.

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Article Synopsis
  • The study addresses the challenge of creating more processable metal-organic frameworks (MOFs), specifically a new Mg-based MOF called NKU-Mg-1.
  • The MOF allows for dynamic control of its size and aggregation state through a self-assembly process, which can be manipulated to achieve different nano-sized colloids.
  • It demonstrates significant potential in applications due to its ability to switch luminescent properties and its incorporation of chiral modules that enhance circularly polarized luminescence (CPL).
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The structural characterization of new materials often poses immense challenges, especially when obtaining single-crystal structures is difficult, which is a common difficulty with covalent organic frameworks (COFs). Despite this, understanding the atomic structure is crucial as it provides insights into the arrangement and connectivity of organic building blocks, offering the opportunity to establish the correlation of structure-function relationships and unravel material properties. In this study, we present an approach for determining the structures of COFs, an integration of electron crystallography and computational intelligence (COF+).

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Tuning the dimensions and molecular packing geometry of crystalline organic frameworks and polymers represents an important challenge for reticular chemistry. Here we show that for extended structures made of 1,3,6,8-tetrakis(4-aminophenyl)pyrene (PyTTA) linked with methoxy group functionalized terephthalaldehyde aldehydes, simple substituents on the aldehyde linker can have profound structure directing effects due to noncovalent interactions. Specifically, reacting 2,3-dimethoxyterephthalaldehyde with PyTTA gives a 2D covalent organic framework with unique AA-inclined-AA stacking and bilayer pyrene motifs, whereas reacting 2,5-dimethoxyterephthalaldehyde with PyTTA gives a 1D crystalline polymer with AB stacking and isolated pyrene motifs.

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Article Synopsis
  • The direct conversion of propylene to propylene oxide (PO) using molecular oxygen offers a highly efficient production method, known as aerobic epoxidation, but faces challenges in balancing conversion rates and PO selectivity.
  • Researchers have found that Ti-Beta zeolites with isolated titanium species can effectively catalyze this reaction, achieving a consistent propylene conversion of 25% along with a PO selectivity of up to 90%, comparable to industrial methods for ethylene.
  • The study highlights that specific titanium sites in the zeolite frameworks facilitate the reaction; these findings may lead to more sustainable practices in PO production within the chemical industry.
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Zeolites are typically synthesized in the presence of strong alkaline or fluoride species, which is not atom-economic for zeolite synthesis due to the high solubility of strong alkaline and fluoride species to silica. One of the solutions for this issue is to reduce solubility of silica in the zeolite synthesis, but it is challenging. Herein, we show that nucleation and growth of zeolites can occur under near neutral conditions, giving an atom-economical synthesis of zeolites with almost full silica utilization due to very low silica solubility.

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The formation of multicarbon products from CO electroreduction is challenging on materials other than Cu-based catalysts. Ag has been known to be a typical metal catalyst, producing CO in CO electroreduction. The formation of C products by Ag has never been reported because the carbon-carbon (C-C) coupling is an unfavorable process due to the high reaction barrier energy of *OCCO.

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Article Synopsis
  • The purification of cyclohexane is crucial for producing various materials but is difficult due to its similarities with benzene.
  • This research showcases a specific zeolite (SSZ-74) that achieves high productivity in separating cyclohexane from benzene, producing ultrapure cyclohexane with very low benzene content.
  • The study combines various advanced techniques, such as DFT calculations and FTIR spectroscopy, to explain how the unique structure of the zeolite enhances its separation capabilities.
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While the majority of knots are made from the metal-template approach, the use of entangled, constrained knotted loops to modulate the coordination of the metal ions remains inadequately elucidated. Here, we report on the coordination chemistry of a 140-atom-long cinquefoil knotted strand comprising five tridentate and five bidentate chelating vacancies. The knotted loop is prepared through the self-assembly of asymmetric "3 + 2" dentate ligands with copper(II) ions that favor five-coordination geometry.

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Chirality is a common phenomenon in nature and plays an important role in the properties of matter. The rational synthesis of chiral compounds and exploration of their applications in various fields require an unambiguous determination of their handedness. However, in many cases, determinations of the chiral crystal structure and chiral morphology have been a challenging task due to the lack of proper characterization methods, especially for nanosized crystals.

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Unraveling the mechanism of chirality transfer across length scales is crucial to the rational development of functional materials with hierarchical chirality. The key obstacle is the lack of structural information, especially at the mesoscopic level. We report herein the structural identification of helical covalent organic frameworks (COFs) with hierarchical chirality, which integrate molecular chirality, channel chirality, and morphology chirality into one crystalline entity.

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Propane dehydrogenation (PDH) reaction has emerged as one of the most promising propylene production routes due to its high selectivity for propylene and good economic benefits. However, the commercial PDH processes usually rely on expensive platinum-based and poisonous chromium oxide based catalysts. The exploration of cost-effective and ecofriendly PDH catalysts with excellent catalytic activity, propylene selectivity, and stability is of great significance yet remains challenging.

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Article Synopsis
  • Two-dimensional conductive metal-organic frameworks (2D-MOFs) show potential for electronics due to their high electrical conductivity but face synthesis challenges due to poor solubility of traditional planar ligands.* -
  • The study introduces a "rotor-stator" molecular design strategy to create 2D-MOFs using a specially designed nonplanar biscarbazole ligand, resulting in high-quality crystals with well-defined structures.* -
  • This new approach was successfully applied to create multiple 2D-MOFs, demonstrating the versatility and effectiveness of the nonplanar ligand design for the construction of crystalline materials.*
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As an important characterization method, pair distribution function (PDF) has been extensively used in structural analysis of nanomaterials, providing key insights into the degree of crystallinity, atomic structure, local disorder etc. The collection of scattering signals with good statistics is necessary for a reliable structural analysis. However, current conventional electron diffraction experiments using PDF (ePDF) are limited in their ability to acquire continuous diffraction rings for large nanoparticles.

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Dynamic 3D covalent organic frameworks (COFs) have shown concerted structural transformation and adaptive gas adsorption due to the conformational diversity of organic linkers. However, the isolation and observation of COF rotamers constitute undergoing challenges due to their comparable free energy and subtle rotational energy barrier. Here, we report the atomic-level observation and structural evolution of COF rotamers by cryo-3D electron diffraction and synchrotron powder X-ray diffraction.

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A multidimensional extra-large pore zeolite with highly hydrothermal stability, denoted as -IRT-HS, has been developed successfully, starting from Ge-rich germanosilicate precursor hydrothermally directed by a small and commercially available piperidinium-type organic structure-directing agent (OSDA). -IRT-HS, with the supermicropores, is structurally analogues to 28-membered ring -IRT topology as confirmed by various spectroscopic techniques. And it is the high-silica (Si/Ge=58) zeolite with the largest pore size as well.

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Selective conversion of syngas to value-added olefins has attracted considerable research interest. Regulating product distribution remains challenging, such as achieving higher olefin selectivity, propylene/ethylene (P/E) and olefin/paraffin (O/P) ratios. A new pentasil zeolite Al-IDM-1 with recently approved -ION structure, composed of 17-membered-ring (MR) extra-large lobed pores and intersected 10-MR medium pores, shows a C selectivity up to 85 % and a high O/P value of 14 in the conversion of syngas when being combined with Zn Al O oxide.

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We report the colloidal synthesis of Bi-doped CsAgNaInCl double perovskite nanoplatelets (NPLs) exhibiting a near-unity photoluminescence quantum yield (PLQY), a record emission efficiency for nanoscale lead-free metal halides. A combination of optical spectroscopies revealed that nonradiative decay processes in the NPL were suppressed, indicating a well-passivated surface. By comparison, nanocubes with the same composition and surface ligands as the NPLs had a PLQY of only 40%.

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Non-oxidative dehydrogenation of propane is a highly efficient approach for industrial preparation of propene that is commonly catalyzed by noble Pt or toxic Cr catalysts and suffers from coking. In this work, ferric catalyst confined in a zeolite framework was synthesized by a hydrothermal procedure. The isolated Fe in the framework formed distorted tetrahedra, which were beneficial for the selective dehydrogenation of propane and reached over 95 % propene selectivity and over 99 % total olefins selectivity.

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Germanosilicate zeolites with various structures have been extensively synthesized, but the syntheses of corresponding zeolite structures in the absence of germanium species remain a challenge. One such example is an ITR zeolite structure, which is a twin of the ITH zeolite structure. Through the modification of a classic organic template for synthesizing ITH zeolites and thus designing a new organic template with high compatibility to ITR zeolite assisted by theoretical simulation, we, for the first time, show the Ge-free synthesis of an ITR structure including pure silica, aluminosilicate, and borosilicate ITR zeolites.

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Elemental phosphorus exhibits fascinating structural varieties and versatile properties. The unique nature of phosphorus bonds can lead to the formation of extremely complex structures, and detailed structural information on some phosphorus polymorphs is yet to be investigated. In this study, we investigated an unidentified crystalline phase of phosphorus, type-II red phosphorus (RP), by combining state-of-the-art structural characterization techniques.

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Article Synopsis
  • The study explores enolimine-ketoenamine tautomerism to create 2D covalent organic frameworks (COFs) with enhanced chemical durability and photoelectronic performance.
  • It faces challenges in controlling tautomeric states and understanding how these structures affect photoelectronic properties due to the dynamic nature of proton transfer.
  • The researchers developed a 3D dynamic COF (dynaCOF-301) that stabilizes and switches its tautomeric forms via structural transformations and interactions with guest molecules, enabling effective chemosensing.
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Three-dimensional covalent organic frameworks (3D COFs) have been of great interest due to their inherent numerous open sites and pore confinement effect. However, it has remained challenging to build 3D frameworks via interdigitation (also known as inclined interpenetration) by generating an entangled network formed by multiple 2D layers inclined with respect to each other. Herein, we report the first case of constructing a 3D COF, termed COF-904, through interdigitating 2D hcb nets, which was formed via [3+2] imine condensation reactions by the use of 1,3,5-triformylbenzene and 2,3,5,6-tetramethyl-1,4-phenylenediamine.

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