Search Results (18)

The microenvironment of the porous channels in enzyme immobilization carriers critically determines the catalytic performance of immobilized enzymes. In this study, we systematically tuned the hydrophobicity/hydrophilicity of the channel microenvironment of hydrogen-bonded organic frameworks (HOFs) by introducing four different substituents (-CH₃, -Cl, -F, -NH₂) at the 2-position of the phenyl ring of the HOF-101 monomer. These HOF-101 derivatives, which are isostructural to the parent HOF-101, were used to immobilize phosphotriesterase (PTE). The enzyme loading efficiencies ranged from 64.7% to 70.7%, indicating that the substituents had little effect on PTE binding, which primarily relies on carboxyl-residue interactions. Kinetic studies revealed that the hydrophilic -NH₂-functionalized HOF-101 (PTE@HOF-101-NH₂) exhibited the highest catalytic efficiency (1.43 × 10⁸ M⁻¹ s⁻¹), 2.27 times that of free PTE, while the hydrophobic -CH₃ analogue showed reduced activity. Notably, PTE@HOF-101-F demonstrated superior acid resistance (70% relative activity at pH 2) and long-term thermal stability (70% activity retention after 6 h at 70 °C), outperforming other derivatives. In contrast, PTE@HOF-101-NH₂ showed the highest activity under mild conditions but suffered from framework dissolution under prolonged harsh treatments. This work demonstrates that fine-tuning the HOF channel microenvironment is an effective strategy to enhance enzyme activity and stability, providing a platform for designing advanced immobilized enzyme systems. Full article

The transition from passive containment to active, responsive management is defining the next generation of intelligent packaging. This evolution creates a critical demand for materials that can be precisely engineered to monitor, regulate, and protect. Hydrogen-bonded organic frameworks (HOFs) have emerged as a uniquely versatile platform in this regard, owing to their synthetically tunable porosity, inherent biocompatibility, and exceptional solution processability derived from reversible supramolecular assembly. This review moves beyond cataloging applications to dissect the fundamental mechanisms by which HOFs enable smart packaging functions, including the following: (i) selective gas capture and atmosphere tailoring via molecular recognition within designed pores; (ii) high-sensitivity optical and electrochemical sensing for real-time quality and safety signaling; and (iii) stimuli-responsive release of active agents (e.g., antimicrobials). We further explore the frontier of integrating HOFs as functional fillers or coatings within polymeric matrices, a key step toward practical devices. Despite challenges such as structural stability and maintaining permanent porosity due to relatively weak hydrogen bonds, this work aims to provide a design blueprint for advancing HOFs from laboratory curiosities to core components of sustainable, multifunctional packaging systems. Full article

Per- and polyfluoroalkyl substances (PFAS) represent a class of highly persistent environmental contaminants with exceptional chemical stability. Efficient removal of PFAS from water poses a significant challenge for the chemical industry and constitutes a critical requirement for sustainable environmental development. Membrane technology has demonstrated considerable potential in water treatment due to its low energy consumption and environmentally friendly characteristics. This review comprehensively summarizes recent advances in emerging metal–organic framework (MOF)-, covalent organic framework (COF)-, and hydrogen-bonded organic framework (HOF)-based membranes for highly efficient separation and catalytic degradation of PFAS. We provide a detailed analysis of design strategies for various organic framework membranes (OFMs) and their synergistic separation mechanisms, including size exclusion, electrostatic interactions, adsorption, as well as catalytic degradation based on advanced oxidation processes. Furthermore, we systematically evaluate the performance and applicability of these membranes in practical aquatic environments. Finally, this review outlines future directions toward developing integrated “separation-degradation” membrane processes for practical applications by discussing current challenges concerning material stability, manufacturing costs, and long-term operational efficiency. This review aims to provide theoretical guidance and technical insights for developing next-generation high-performance membranes for PFAS removal. Full article

The development of stable and sensitive fluorescent sensors for metal ion detection remains a challenge in materials chemistry. Although hydrogen-bonded organic frameworks (HOFs) have shown great potential in luminescent applications, their practical use is often limited by structural instability. In this work, we present a novel charge-assisted HOF, termed FDU-HOF-21 ([H(NH₂Bpy)]₂(TPE)), constructed from a tetraphenylethylene (TPE)-based carboxylic acid ligand (H₄TCPE) and 2,2′-bipyridine-5,5′-diamine (NH₂Bpy). Single-crystal X-ray diffraction (SCXRD) reveals a stable three-dimensional framework stabilized by an extensive hydrogen-bonding network and reinforced by charge-assisted hydrogen bonds (CAHBs), and it exhibits exceptional stability across various solvents and pH conditions. Moreover, FDU-HOF-21 serves as a highly sensitive and selective fluorescent turn-on sensor for Al³⁺ ions, with a lowest limit of detection (LOD) of 1.7 × 10⁻⁶ M. Characterization and time-dependent density functional theory (TDDFT) calculations reveal that the fluorescence enhancement originates from the suppression of non-radiative decay likely due to the reduction in intermolecular charge transfer (Inter-CT) during the emission process, coupled with the restricted intramolecular rotation upon Al³⁺ chelation. Full article

The photo-Fenton process is an advanced oxidation method widely employed in environmental remediation. Herein, we developed a novel metal–organic framework@hydrogen-bonded organic framework (MOF/HOF) composite with excellent photo-Fenton-like activity for the efficient degradation of organic dye methylene blue (MB). Cu-based MOF (CuBTC) was firstly prepared via the solvothermal method, then melamine (MA) and trimesic acid (TMA)-based HOF (MA-TMA) was grown in situ on CuBTC with hydrogen bonding interactions to produce the MOF/HOF composite CuBTC-MA. The CuBTC-MA composite could catalyze H₂O₂ to produce active substances for efficient MB degradation. The degradation rate constant of the CuBTC-MA composite was 4.4 times and 16.7 times higher than that of CuBTC and MA-TMA. The remarkably enhanced performance was attributed to the synergistic effect between the efficient separation of electron–holes supported by the type-II heterojunction structure of the CuBTC-MA composite and the Cu(I)/Cu(II) inter-conversion. The CuBTC-MA composite demonstrated exceptional repeatability and maintained a stable performance across a broad pH range. This study provided a novel paradigm for engineering heterogeneous MOF/HOF heterostructures, demonstrating significant potential in advancing photo-Fenton-like catalytic systems for the efficient environmental remediation of organic pollutants through synergistic charge separation and radical generation mechanisms. Full article

Lanthanide hydrogen-bonded organic frameworks (Ln-HOFs) integrating luminescent and proton-conductive properties hold significant promise for multifunctional sensing and energy applications, yet their development remains challenging due to the difficulty of balancing structural stability and functional diversity. In this context, this study successfully synthesized a novel neodymium(III)-based hydrogen-bonded framework material, formulated as {Nd(H₂O)₃(4-CPCA)[H(4-CPCA)]∙H₂O}ₙ (SNUT-15), via hydrothermal assembly using 1-(4-carboxyphenyl)-4-oxo-1,4-dihydropyridazine-3-carboxylic acid (H₂(4-CPCA)) as the ligand. Single-crystal X-ray diffraction analysis revealed a rare two-dimensional hydrogen-bonded bilayer structure stabilized by π-π stacking interactions and intermolecular hydrogen bonds. Hirshfeld surface analysis further corroborated the structural characteristics of this material. Moreover, leveraging the superior luminescent properties of lanthanide elements, this crystalline material exhibits dual functionality: selective fluorescence quenching toward Fe³⁺, La³⁺, and Mn²⁺ (with detection limits of 1.74 × 10⁻⁴, 1.88 × 10⁻⁴, and 3.57 × 10⁻⁴ mol·L⁻¹, respectively), as well as excellent proton conductivity reaching 7.92 × 10⁻³ S cm⁻¹ under conditions of 98% relative humidity and 353 K (80 °C). As a multifunctional neodymium(III)-based HOF material, SNUT-15 demonstrates its potential for applications in environmental monitoring and solid-state electrolytes, providing valuable insights into the rational design of lanthanide-containing frameworks. Full article

Hydrogen-bonded organic framework (HOF) materials are typically formed by the self-assembly of small organic units (synthons) with specific functional groups through hydrogen bonding or other interactions. HOF is commonly used as an electrolyte for batteries. Well-designed HOF materials can enhance the proton exchange rate, thereby boosting battery performance. This paper reviews recent advancements in the continuous synthesis of HOF synthons, in the continuous synthesis of HOF’s unit small molecules enabling the multi-step, rapid, and in situ synthesis of synthons, such as carboxylic acid, diaminotriazine (DAT), urea, guanidine, imidazole, pyrazole, pyridine, thiazole, triazole, and tetrazole, with online monitoring. Continuous flow reactors facilitate fast chemical reactions and precise microfluidic control, offering superior reaction speed, product yield, and selectivity compared to batch processes. Integrating the continuous synthesis of synthons with the construction of HOF materials on a single platform is essential for achieving low-cost, safe, and efficient processing, especially for reactions involving toxic, flammable, or explosive substances. Full article

Small bifunctional molecules are attractive for use as models in different areas of knowledge. How can their functional groups interact in solids? This is important to know for the prediction of the physical and chemical properties of the materials based on them. In this study, two new hydrogen-bonded organic frameworks (HOFs) based on sterically demanding molecular compounds, bis(1-hydroxy-2-methylpropane-2-aminium) sulfate (1) and 2-methyl-4-oxopentan-2-aminium hydrogen ethanedioate hydrate (2), were synthesized and fully characterized by means of FTIR and NMR spectroscopies, as well as by X-ray powder diffraction and thermogravimetric analyses. Their molecular and crystal structures were established through single-crystal X-ray diffraction analysis. It was shown that both compounds have a layered structure due to the formation of a 2D hydrogen-bonding network, the layers being linked by systematically arranged Van der Waals contacts between the methyl groups of organic cations. To unveil some dependencies between the chemical nature of bifunctional molecules and their solid structure, Hirschfeld surface (HS) analysis was carried out for HOFs 1, 2, and their known congeners 1-hydroxy-2-methylpropan-2-aminium hemicarbonate (3) and 1-hydroxy-2-methylpropan-2-aminium (1-hydroxy-2-methylpropan-2-yl) carbamate (4). HS was performed to quantify and visualize the close intermolecular atomic contacts in the crystal structures. It is clearly seen that H–H contacts make the highest contributions to the amino alcohol based compounds 1, 3 and 4, with a maximal value of 65.2% for compound 3 having CO₃²⁻ as a counterion. A slightly lower contribution of H–H contacts (64.4%) was found for compound 4, in which the anionic part is represented by 1-hydroxy-2-methylpropan-2-yl carbamate. The significant contribution of the H–H contacts in the bifunctional moieties is due to the presence of a quaternary carbon atom with a short three-carbon chain. Full article

Hydrogen-bonded organic frameworks (HOFs) are a kind of crystalline porous material that have shown great potential for photocatalysis on account of their mild synthesis conditions and high crystallinity. Perylene-based photocatalysts have great potential for photocatalytic H₂O₂ production due to their excellent photochemical stability and broad spectral absorption. In this work, we designed and synthesized a high crystalline perylene-based HOF (PTBA) and an amorphous analog sample PTPA for photocatalytic H₂O₂ evolution. Under visible light irradiation, PTBA shows a higher photocatalytic H₂O₂ production rate of 2699 μmol g⁻¹ h⁻¹ than PTPA (2176 μmol g⁻¹ h⁻¹) and an apparent quantum yield (AQY) of 2.96% at 500 nm. The enhanced photocatalytic performance of PTBA is attributed to the promotion of the separation and transfer of photocarriers due to its high crystallinity. This work provides a precedent for the application of HOFs in the field of photocatalytic H₂O₂ generation. Full article

The hydrogen-bonded organic frameworks (HOFs) are a class of porous materials with crystalline frame structures, which are self-assembled from organic structures by hydrogen bonding in non-covalent bonds π-π packing and van der Waals force interaction. HOFs are widely used in environmental remediation due to their high specific surface area, ordered pore structure, pore modifiability, and post-synthesis adjustability of various physical and chemical forms. This work summarizes some rules for constructing stable HOFs and the synthesis of HOF-based materials (synthesis of HOFs, metallized HOFs, and HOF-derived materials). In addition, the applications of HOF-based materials in the field of environmental remediation are introduced, including adsorption and separation (NH₃, CO₂/CH₄ and CO₂/N₂, C₂H₂/C₂H_e and C_eH₆, C₂H₂/CO₂, Xe/Kr, etc.), heavy metal and radioactive metal adsorption, organic dye and pesticide adsorption, energy conversion (producing H₂ and CO₂ reduced to CO), organic dye degradation and pollutant sensing (metal ion, aniline, antibiotic, explosive steam, etc.). Finally, the current challenges and further studies of HOFs (such as functional modification, molecular simulation, application extension as remediation of contaminated soil, and cost assessment) are discussed. It is hoped that this work will help develop widespread applications for HOFs in removing a variety of pollutants from the environment. Full article

The weak bonding energy and flexibility of hydrogen bonds can hinder the long-term use of hydrogen-bonded organic framework (HOF) materials under harsh conditions. Here we invented a thermal-crosslinking method to form polymer materials based on a diamino triazine (DAT) HOF (FDU-HOF-1), containing high-density hydrogen bonding of N-H⋯N. With the increase of temperature to 648 K, the formation of –NH– bonds between neighboring HOF tectons by releasing NH₃ was observed based on the disappearance of the characteristic peaks of amino groups on FDU-HOF-1 in the Fourier transform infrared (FTIR) and solid-state nuclear magnetic resonance (ss-NMR). The variable temperature PXRD indicated the formation of a new peak at 13.2° in addition to the preservation of the original diffraction peaks of FDU-HOF-1. The water adsorption, acid-base stability (12 M HCl to 20 M NaOH) and solubility experiments concluded that the thermally crosslinked HOFs (TC-HOFs) are highly stable. The membranes fabricated by TC-HOF demonstrate the permeation rate of K⁺ ions as high as 270 mmol m⁻² h⁻¹ as well as high selectivity of K⁺/Mg²⁺ (50) and Na⁺/Mg²⁺ (40), which was comparable to Nafion membranes. This study provides guidance for the future design of highly stable crystalline polymer materials based on HOFs. Full article

Hydrogen-bonded organic frameworks (HOFs), as an emerging porous material, have attracted increasing research interest in fluorescence sensing due to their inherent fluorescence emission units with unique physicochemical properties. Herein, based on the organic building block 3,3′,5,5′-tetrakis-(4-carboxyphenyl)-1,1′-biphenyl (H₄TCBP), the porous material HOF-TCBP was successfully synthesized using hydrogen bond self-assembly in a DMF solution. The fluorescence properties of the HOF-TCBP solution showed that when the concentration was high, excimers were easily formed, the PL emission was red-shifted, and the fluorescence intensity became weaker. HOF-TCBP showed good sensitivity and selectivity to metal ions Fe³⁺, Cr³⁺, and anion Cr₂O₇²⁻. In addition, HOF-TCBP can serve as a label-free fluorescent sensor material for the sensitive and selective detection of dopamine (DA). HOF-based DA sensing is actually easy, low-cost, simple to operate, and highly selective for many potential interfering substances, and it has been successfully applied to the detection of DA in biological samples with satisfactory recoveries (101.1–104.9%). To our knowledge, this is the first report of HOF materials for efficient detection of the neurotransmitter dopamine in biological fluids. In short, this work widely broadens the application of HOF materials as fluorescent sensors for the sensing of ions and biological disease markers. Full article

Lanthanide hydrogen-bonded organic frameworks (LnHOFs) are recently emerging as a novel versatile class of multicomponent luminescent materials with promising potential applications in optics and photonics. Trivalent europium (Eu³⁺) incorporated polymeric hydrogen-bonded triazine frameworks (PHTF:Eu) have been successfully obtained via a facile and low-cost thermal pyrolysis route. The PHTF:Eu material shows a porous frame structure principally composed of isocyanuric acid and ammelide as a minor constituent. Intense red luminescence with high colour-purity from Eu³⁺ is obtained by exciting over a broad absorption band peaked at 300 nm either at room or low temperature. The triazine-based host works as excellent optical antenna towards Eu³⁺, yielding ~42% sensitization efficiency (η_sens) and an intrinsic quantum yield of Eu³⁺ emission (Φ_Eu) as high as ~46%. Temperature-dependent emission studies show that PHTF:Eu displays relatively high optical stability at elevated temperatures in comparison to traditional inorganic phosphors. The retrieved activation energy of 89 meV indicates that thermal quenching mechanisms are attributed to the intrinsic energy level structure of the metal-triazine assembly, possibly via a thermally activated back transfer to ligand triplet or CT states. Finally, by using an innovative approach based on excitation spectra, we demonstrate that PHTF:Eu can work as a universal primary self-referencing thermometer based on a single-emitting center with excellent relative sensitivity in the cryogenic temperature range. Full article

Hydrogen-bonded organic frameworks (HOFs), as a newly developed porous material, have been widely used in various fields. To date, several organic building units (OBUs) with tri-, tetra-, and hexa-carboxylic acid synthons have been applied to synthesize HOFs. To our knowledge, di-carboxylic acids have rarely been reported for the construction of HOFs, in particular, di-carboxylic acid-based HOFs with fluorescence sensing properties have not been reported. In this study, a rare example of a di-carboxylic acid-based, luminescent three-dimensional hydrogen-bonded organic framework has been successfully constructed and structurally characterized; it has a strong electron-rich property originated from its organic linker 9-phenylcarbazole-3,6-dicarboxylic acid. It represents the first example of HOF-based sensors for the highly selective and sensitive detection of PA (Picric acid) with reusability; the LOD is less than 60 nM. This work thus provides a new avenue for the fabrication of fluorescent HOFs sensing towards explosives. Full article

Hydrogen-bonded organic frameworks (HOFs) have attracted renewed attention as another type of promising candidates for functional porous materials. In most cases of HOF preparation, the applied molecular design principle is based on molecules with rigid π-conjugated skeleton together with more than three H-bonding groups to achieve 2D- or 3D-networked structures. However, the design principle does not always work, but results in formation of unexpected structures, where subtle structural factors of which we are not aware dictate the entire structure of HOFs. In this contribution, we assess recent advances in HOFs, focusing on those composed of hexatopic building block molecules, which can provide robust frameworks with a wide range of topologies and properties. The HOFs described in this work are classified into three types, depending on their H-bonded structural motifs. Here in, we focus on: (1) the chemical aspects that govern their unique fundamental chemistry and structures; and (2) their photophysics at the ensemble and single-crystal levels. The work addresses and discusses how these aspects affect and orient their photonic applicability. We trust that this contribution will provide a deep awareness and will help scientists to build up a systematic series of porous materials with the aim to control both their structural and photodynamical assets. Full article