Xinle Li

The mechanosynthesis of imine-linked covalent organic frameworks (COFs) has garnered significant attention. Nevertheless, existing reports predominantly rely on imine condensation and produce hexagonal frameworks. Here, we introduce the imine exchange reaction as a powerful synthetic toolkit for COF mechanochemistry, wherein four 2D imine-linked COFs featuring diverse topologies (kgm, sql, and hcb) were synthesized within an hour under ambient conditions. The resultant COFs exhibit high crystallinity and surface areas (860–1380 m²/g), far exceeding those (20–505 m²/g) made by direct condensation. Notably, an aggregation-induced emission (AIE)-based COF was obtained in just 30 min, whereas it remained inaccessible via mechanochemical direct condensation. Time-resolved ¹H NMR studies in a mechanochemical model reaction reveal much slower imine exchange kinetics than direct condensation, which facilitates effective error correction during COF growth and ultimately yields higher-quality frameworks. This work establishes a rapid, green, and generalizable route to high-quality imine-linked COFs superior to those produced by direct condensation.

This study demonstrates a mechanochemical amorphous-to-crystalline transformation strategy that enables the rapid, ambient synthesis of nine imine-linked COFs with diverse topologies ( hcb , sql , kgm , and dia ), functionalities, and dimensionalities.

This review highlights deep eutectic solvents as sustainable media for covalent organic framework (COF) synthesis, examining their roles, benefits, mechanisms, limitations, and potential for scalable COF fabrication.

We present the first ambient mechanosynthesis of 16 flexible covalent organic frameworks (COFs) within an hour. Notably, one representative COF exhibited a high iodine uptake capacity of ∼4.3 g g⁻¹ from aqueous solutions and 5.97 g g⁻¹ from vapor.

Doping gold nanoparticles within covalent organic frameworks (AuNPs@COFs) has garnered enormous momentum due to their unique properties and broad applications. Nevertheless, prevailing multi‐step synthesis is plagued with low time efficiency, eco‐unfriendliness, and tedious protocols. Herein, we introduce a rapid, sustainable, scalable, one‐step mechanochemical strategy for synthesizing up to four AuNPs‐doped COFs via steel ball milling within an hour under ambient conditions. This approach overcomes the synthetic barriers of conventional multi‐step solution‐based methods, such as extended reaction times (5 days), milligram scale, the use of toxic solvents, elevated temperatures, and reliance on external reducing agents. One exemplary AuNPs@COF (AuNPs@DMTP‐TPB) exhibits high crystallinity, porosity, small AuNP size, and uniform dispersion (5.4±0.6 nm), surpassing its counterpart synthesized via multi‐step solution‐based methods (6.4±1.1 nm). Notably, the gram‐scale synthesis of AuNPs@DMTP‐TPB can be successfully achieved. Control experiments suggest that the in situ formation of AuNPs is attributed to the galvanic reduction of gold precursor by stainless steel apparatus. As a proof‐of‐concept catalytic application, AuNPs@DMTP‐TPB demonstrates remarkable catalytic activity and recyclability for the aqueous reduction of 4‐nitrophenol under ambient conditions. This study provides an environmentally benign and fast pathway to synthesize AuNPs@COFs via mechanochemistry for the first time, opening tremendous possibilities for heterogeneous catalysis and beyond.

This study explores an investigation of the crystallographic, electronic, and magnetic properties of the europium-based bismuth selenide compound Eu₄Bi₆Se₁₃, with particular focus on its magnetic anisotropy. This compound adopts a monoclinic crystal structure classified under the P2₁/m space group (#11). It exhibits distinctive structural features, including substantial Eu-Se coordination numbers (6 and 8), Bi-Se ladders, and linear chains of Eu atoms that propagate along the b-axis. Electronic resistivity assessments indicate that Eu₄Bi₆Se₁₃ exhibits metallic behavior. As the magnetic field is oriented along the b-axis, magnetic characterization reveals uniaxial magnetic anisotropy, with metamagnetic transitions appearing at approximately 12 kOe and a lower field. In the field below 10 kOe, the spin-flop transition is observed with possible domain-induced hysteresis. This behavior supports the identification of metamagnetic features in field-dependent measurements attributable to the europium spins.

Article Andrew Lamkins ^1,2, Charles J. Ward ^1,2, Jeffrey T. Miller ³, Ziad Alsudairy ⁴, Xinle Li ⁴, Joseph Thuma ^1,2, Ruoyu Cui ^1,2, Xun Wu ^1,2, Levi M. Stanley ¹ and Wenyu Huang ^1,2,* ¹ Department of Chemistry, Iowa State University, Ames, IA 50010, USA ² Ames Laboratory, U.S. Department of Energy, Ames, IA 50010, USA ³ Davidson School of Chemical Engineering, Purdue University, West Lafayette, IN 47907, USA ⁴ Department of Chemistry, Clark Atlanta University, Atlanta, GA 30314, USA * Correspondence: whuang@iastate.edu Received: 3 December 2024; Revised: 30 December 2024; Accepted: 3 January 2025; Published: 10 January 2025 Abstract: Controlling the size and distribution of metal nanoparticles is one of the simplest methods of tuning the catalytic properties of a material. For a nanocrystal particle, the ratio of edge-to-terrace sites can be critical in determining its catalytic activity and selectivity to desired products. To study these effects, we have developed a simple impregnation method of controlling the dispersion of rhodium atoms at the same metal loading in the range of nanoparticles less than 10 nm. Rh precursor salts are loaded onto inert SBA-15, and increasing the ratio of chloride to acetylacetonate salts improves the dispersion of rhodium atoms to form small Rh nanoparticles. Extensive characterization of the size-controlled catalysts, including XAS and in-situ CO-DRIFTS studies, has been performed to characterize the structure of Rh nanoparticles. Applying these catalysts to the hydroformylation of styrene, we observed that turnover frequency increases with decreasing particle size from 6.4 to 1.6 nm. When applied to hydroformylation reactions, we achieved a high branched product selectivity and successfully demonstrated a route to synthesizing the pain relief drug ibuprofen. This simple method can also synthesize Pt and Pd nanoparticles between 2–10 nm.

The rapid and environmentally benign synthesis of metal‐immobilized covalent organic frameworks (metal/COFs) for heterogeneous catalysis is a pervasive challenge, as the mainstream synthesis is exceedingly time‐consuming (up to four days) and demands the use of hazardous solvents. Herein, we describe a sustainable and efficient one‐step sonochemical strategy for constructing diverse palladium (II)‐immobilized COFs (Pd(II)/COFs). By merging the sonochemistry‐assisted COF synthesis and in situ Pd (II) immobilization into a single step, this strategy enables the rapid formation of Pd(II)/COF hybrids within an hour under ambient conditions using water as the solvent. Notably, gram‐scale synthesis of Pd(II)/COFs is achievable. The resulting Pd(II)/COFs exhibit superb crystallinity and high surface area, leading to remarkable activity, excellent functionality tolerance, and high recyclability for the Suzuki–Miyaura cross‐coupling reaction of aryl bromides and arylboronic acids at room temperature. This one‐step sonochemical strategy effectively addresses the long‐lasting limitations of traditional multistep synthesis, paving a fast and sustainable avenue to diversified metal/COF hybrids for heterogeneous catalysis and potentially other applications.

Metal‐encapsulated covalent organic frameworks (metal/COFs) represent an emerging paradigm in heterogeneous catalysis. However, the time‐intensive (usually 4 or more days) and tedious multi‐step synthesis of metal/COFs remains a significant stumbling block for their broad application. To address this challenge, we introduce a facile microwave‐assisted in situ metal encapsulation strategy to cooperatively combine COF formation and in situ palladium(II) encapsulation in one step. With this unprecedented approach, we synthesize a diverse range of palladium(II)‐encapsulated COFs (termed Mw‐Pd/COF) in the air within just an hour. Notably, this strategy is scalable for large‐scale production (~0.5 g). Leveraging the high crystallinity, porosity, and structural stability, one representative Mw‐Pd/COF exhibits remarkable activity, functional group tolerance, and recyclability for the Suzuki‐Miyaura coupling reaction at room temperature, surpassing most previously reported Pd(II)/COF catalysts with respect to catalytic performance, preparation time, and synthetic ease. This microwave‐assisted in situ metal encapsulation strategy opens a facile and rapid avenue to construct metal/COF hybrids, which hold enormous potential in a multitude of applications including heterogeneous catalysis, sensing, and energy storage.