Hydrogen-Bonded Organic Framework Microlasers with Conformation-Induced Color-Tunable Output

Monochromatic Responsive HOF Heterostructures via VIA-Group-Based Framework Hybridization for Fully-Covert Photonic Barcode

Luminescent responsive heterostructures with region-domained emission and integrated responsiveness exhibit great potential in information security, but always suffer from the direct exposure of fingerprint information at the initial state, making it easy to decode the hidden confidential information. Herein, the first monochromatic responsive hydrogen-bonded organic framework (HOF) heterostructures are reported based on VIA-group-based framework hybridization toward fully-covert photonic barcodes. Designed HOF blocks with different VIA-group elements are integrated via a configuration-assimilation-based assembly method to generate the intrinsic monochromatic HOF heterostructures. Differentiated electronegativity of VIA-group elements endows each HOF block with distinct bonding stability, which triggers different responsive actions to the same stimuli, finally forming the multicolor emission mode at a responsive state. These monochromatic responsive HOF heterostructures can effectively hide the intrinsic fingerprint information, which further demonstrates the fully-covert photonic coding capability as high-security anti-counterfeiting labels. These findings offer novel insight on the exploitation of smart-responsive hetero-HOF systems for advanced information encryption and anticounterfeiting applications.

Mechanochromic Organic Micro-Laser

This work presents the first demonstration of a mechanochromic organic micro-laser, which exhibits remarkable wide range pressure sensing characteristics. The gain material, pinacolato boronate ester functionalized anthanthrene (AnBPin), is designed by incorporating mechanofluorochromic (MFC) properties into organic laser dye. The AnBPin exhibits a reversible transition between green and orange fluorescence upon grinding annealing and recrystallization cycle, and its micro-crystal exhibits typical organic micro-laser behaviors. Applying localized mechanical pressure as low as 0.1 MPa inhibits micro-laser behavior at the given spot. In contrast, under 1 to 2 GPa hydrostatic pressure, the organic laser maintains narrow emission while showing a pressure-dependent shift in emission wavelength. By combining theory and experimentation, we attribute the unusual pressure-correlated emission spectroscopy to the unique interleaved locked crystal structure. Understanding the mechanochromic laser behavior in AnBPin micro-crystals under an unprecedented pressure range significantly expands the family of organic micro-lasers and provides a new route for wide-range photonic pressure detection.

Fluorescent Porous Materials Based on Aggregation-induced Emission for Biomedical Applications

Fluorescent porous materials based on aggregation-induced emission (AIE) are growing into a sparkling frontier in biomedical applications. Exploring those materials represents a win-win integration and has recently progressed at a rapid pace, mainly benefiting from intrinsic advantages including tunable pore size and structure, strong guest molecule encapsulation ability, superior biocompatibility, and photophysical outcomes. With the great significance and rapid progress in this area, this review provides an integrated picture on AIE luminogen-based porous materials. It encompasses inorganic, organic, and inorganic-organic porous materials, exploring fundamental concepts and the relationship between AIE performance and material design and highlighting significant breakthroughs and the latest trends in biomedical applications. In addition, some critical challenges and future perspectives in the development of AIE luminogen-based porous materials are also discussed.

Iron modified hydrogen-bonded organic framework as fluorescent sensor for ascorbic acid detection

Herein, iron modified hydrogen-bonded organic framework (Fe-HOF) was successfully prepared by introducing the yellow-green fluorescent ligand 2,5-dihydroxyterephthalic acid into HOF and then modifying Fe3+. A simple turn-on fluorescence strategy is proposed for the detection of ascorbic acid (AA) based on Fe-HOF. Fe3+ could effectively quench fluorescence emission of HOF. In the presence of AA, Fe3+ was reduced to Fe2+, which led to the fluorescence recovery of HOF, thus realizing the fluorescence quantitative detection of AA. These fluorescence responsive behaviors of Fe-HOF ensure fluorescence assay of AA within 0.5 - 8 μM, along with a limit of detection (LOD) of 0.14 μM. The sensing platform could realize the rapid detection of ascorbic acid in vitamin C pills, tablets and beverages in the detection of ascorbic acid with good recoveries.

A Hydrogen-Bonded Organic Framework Based on Triphenylamine for Photocatalytic Silane Hydroxylation

Employing hydrogen-bonded organic frameworks (HOFs) as mild photocatalysts for organic conversions is still considerably challenging. In this work, we synthesized a hydrogen-bonded organic framework (HOF-16) and achieved the photocatalytic oxidation of silanes to generate silanols. Considering the constraints imposed by the framework structure, a significant improvement in the efficacy of singlet oxygen (1O2) generation is observed. HOF-16 exhibits remarkable photocatalytic performance when it comes to silane hydroxylation, displaying high efficiency, low catalyst loading, and good recyclability. This research highlights the immense potential of HOFs in the realm of organic photocatalysis.

Structural Design and Energy and Environmental Applications of Hydrogen-Bonded Organic Frameworks: A Systematic Review

Hydrogen-bonded organic frameworks (HOFs) are emerging porous materials that show high structural flexibility, mild synthetic conditions, good solution processability, easy healing and regeneration, and good recyclability. Although these properties give them many potential multifunctional applications, their frameworks are unstable due to the presence of only weak and reversible hydrogen bonds. In this work, the development history and synthesis methods of HOFs are reviewed, and categorize their structural design concepts and strategies to improve their stability. More importantly, due to the significant potential of the latest HOF-related research for addressing energy and environmental issues, this work discusses the latest advances in the methods of energy storage and conversion, energy substance generation and isolation, environmental detection and isolation, degradation and transformation, and biological applications. Furthermore, a discussion of the coupling orientation of HOF in the cross-cutting fields of energy and environment is presented for the first time. Finally, current challenges, opportunities, and strategies for the development of HOFs to advance their energy and environmental applications are discussed.

Charge-Assisted Ionic Hydrogen-Bonded Organic Frameworks: Designable and Stabilized Multifunctional Materials

Hydrogen-bonded organic frameworks (HOFs) are a class of crystalline framework materials assembled by hydrogen bonds. HOFs have the advantages of high crystallinity, mild reaction conditions, good solution processability, and reproducibility. Coupled with the reversibility and flexibility of hydrogen bonds, HOFs can be assembled into a wide diversity of crystalline structures. Since the bonding energy of hydrogen bonds is lower than that of ligand and covalent bonds, the framework of HOFs is prone to collapse after desolventisation and the stability is not high, which limits the development and application of HOFs. In recent years, numerous stable and functional HOFs have been developed by π-π stacking, highly interpenetrated networks, charge-assisted, ligand-bond-assisted, molecular weaving, and covalent cross-linking. Charge-assisted ionic HOFs introduce electrostatic attraction into HOFs to improve stability while enriching structural diversity and functionality. In this paper, we review the development, the principles of rational design and assembly of charge-assisted ionic HOFs, and introduces the different building block construction modes of charge-assisted ionic HOFs. Highlight the applications of charge-assisted ionic HOFs in gas adsorption and separation, proton conduction, biological applications, etc., and prospects for the diverse design of charge-assisted ionic HOFs structures and multifunctional applications.

Smart-Responsive HOF Heterostructures with Multiple Spatial-Resolved Emission Modes toward Photonic Security Platform

Luminescent hydrogen-bonded organic frameworks (HOFs) with the unique dynamics and versatile functional sites hold great potential application in information security, yet most of responsive HOFs focus on the single-component framework with restrained emission control, limiting further applications in advanced confidential information protection. Herein, the first smart-responsive HOF heterostructure with multiple spatial-resolved emission modes for covert photonic security platform is reported. The HOF heterostructures are prepared by integrating different HOFs into a single microwire based on a hydrogen-bond-assisted epitaxial growth method. The distinct responsive behaviors of HOFs permit the heterostructure to simultaneously display the thermochromism via the framework transformation and the acidichromism via the protonation effect, thus generating multiple emission modes. The dual stimuli-controlled spatial-resolved emission modes constitute the fingerprint of a heterostructure, and enable the establishment of the smart-responsive photonic barcode with multiple convert states, which further demonstrate the dynamic coding capability and enhanced security in anticounterfeiting label applications. These results offer a promising route to design function-oriented smart responsive HOF microdevices toward advanced anticounterfeiting applications.

Luminescent Porous Organic Crystals for Adsorptive Separation of Toluene and Methylcyclohexane

A butterfly-shaped phenothiazine derivative, PTTCN, was synthesized to obtain pure organic porous crystals for the highly efficient absorptive separation of toluene (Tol) and methylcyclohexane (Mcy). Due to the presence of three polar cyano groups and nonplanar conformation, these molecules self-assembled into a hydrogen-bonded organic framework (X-HOF-5) with distinct cavities capable of accommodating Tol molecules through multiple hydrogen-bonding interactions. Upon solvent removal via heating, the activated X-HOF-5 retained its cavity structure albeit with altered stacking arrangements, accompanied by a remarkable fluorescent color change from cyan to green. X-HOF-5a can undergo a phase transformation into X-HOF-5 upon reabsorption of Tol, while exhibiting no accommodation of Mcy due to the weak intermolecular interaction between PTTCN and Mcy. This suggests that the activated HOF material prefers Tol over Mcy. Moreover, X-HOF-5a may selectively accommodate Tol in a Tol/Mcy equimolar mixture, and the purity of Tol can reach 97% after release from the framework. Additionally, it is noteworthy that the HOF material exhibits recyclability without any discernible loss in performance.

Flexible Luminescent Hydrogen-bonded Organic Framework for the Separation of Benzene and Cyclohexane

A nonplanar phenothiazine derivative with three cyano moieties (PTTCN) is designed and synthesized to achieve functional crystals for absorptive separation of benzene and cyclohexane. PTTCN can crystallize into two kinds of crystals with different fluorescence colors in different solvent systems. The molecules in two crystals are in different stereo isomeric forms of nitrogen, quasi axial (ax), and quasi equatorial (eq). The crystals with blue fluorescence in ax form may selectively adsorb benzene by a single-crystal-to-single-crystal (SCSC) transformation, but separated benzene from a benzene/cyclohexane equimolar mixture with a low purity of 79.6%. Interestingly, PTTCN molecules with eq form and benzene co-assembled to construct a hydrogen-bonded framework (X-HOF-4) with S-type solvent channels and yellow-green fluorescence, and can release benzene to form nonporous guest-free crystal under heating. Such nonporous crystals strongly favor aromatic benzene over cyclohexane and may selectively reabsorb benzene from benzene/cyclohexane equimolar mixture to recover original framework, and the purity of benzene can reach ≈96.5% after release from framework. Moreover, reversible transformation between the nonporous crystals and the guest-containing crystals allows the material to be reused.

A Multistimuli Responsive, Flexible Luminescent Framework and Its Applicability in Anticounterfeiting

A linear distyrylanthracene derivative (DDATAn) with two diaminotriazine (DAT) groups acting as the hydrogen bond (H-bond) units was designed and synthesized in order to construct flexible organic porous crystals. H-bonds between the DAT moieties helped the molecules to construct a double interpenetrated two-dimensional layer, and the stacking between layers provided a H-bonded organic framework (X-HOF-3) with one-dimensional solvent channels. When X-HOF-3 was placed in contact with methanol, the fluorescent colors of the HOF exhibited an apparent bathochromic shift. More interestingly, the methanol-activated HOF was able to rapidly adsorb water from the air, which was accompanied by a change in fluorescent color from yellow to red. Under heating, water was released from the HOF and the fluorescent color returned to yellow. Water molecules in the pores were also able to be released after an applied mechanical force disrupted the ordered structure of the HOF. Based on these stimuli-responsive properties, these HOFs can be used as advanced functional materials in anticounterfeiting applications.

Hybrid Hydrogen-Bonded Organic Frameworks: Structures and Functional Applications

As a new class of porous crystalline materials, hydrogen-bonded organic frameworks (HOFs) assembled from building blocks by hydrogen bonds have gained increasing attention. HOFs benefit from advantages including mild synthesis, easy purification, and good recyclability. However, some HOFs transform into unstable frameworks after desolvation, which hinders their further applications. Nowadays, the main challenges of developing HOFs lie in stability improvement, porosity establishment, and functionalization. Recently, more and more stable and permanently porous HOFs have been reported. Of all these design strategies, stronger charge-assisted hydrogen bonds and coordination bonds have been proven to be effective for developing stable, porous, and functional solids called hybrid HOFs, including ionic and metallized HOFs. This Review discusses the rational design synthesis principles of hybrid HOFs and their cutting-edge applications in selective inclusion, proton conduction, gas separation, catalysis and so forth.

Polarity-Evolution Control and Luminescence Regulation in Multiple-Site Hydrogen-Bonded Organic Frameworks

Hydrogen-bonded organic frameworks (HOFs) have shown great potential in separation, sensing and host-guest chemistry, however, the pre-design of HOFs remains challenging due to the uncertainty of solvents' participation in framework formation. Herein, the polarity-evolution-controlled framework/luminescence regulation is demonstrated based on multiple-site hydrogen-bonded organic frameworks. Several distinct HOFs were prepared by changing bonding modes of building units via the evolution of electrostatic forces induced by various solvent polarities. High-polar solvents with strong electrostatic attraction to surrounding units showed the tendency to form cage structures, while low-polar solvents with weak electrostatic attraction only occupy hydrogen-bond sites, conducive to the channel formation. Furthermore, the conformation of optical building unit can be adjusted by affecting the solvent polarity, generating different luminescence outputs. These results pave the way for the rational design of ideal HOFs with on-demand framework regulation and luminescence properties.

Non-covalent interactions (NCIs) in π-conjugated functional materials: advances and perspectives

The design and development of functional materials with real-life applications are highly demanding. Understanding and controlling inter- and intra-molecular interactions provide opportunities to design new materials. A judicious manipulation of the molecular structure significantly alters such interactions and can boost selected properties and functions of the material. There is burgeoning evidence of the beneficial effects of non-covalent interactions (NCIs), showing that manipulating NCIs may generate functional materials with a wide variety of physical properties leading to applications in catalysis, drug delivery, crystal engineering, etc. This prompted us to review the implications of NCIs on the molecular packing, optical properties, and applications of functional π-conjugated materials. To this end, this tutorial review will cover different types of interactions (electrostatic, π-interactions, metallophilic, etc.) and their impact on π-conjugated materials. Attempts have also been made to delineate the effects of weak interactions on opto-electronic (O-E) applications.

Multifunctional Porous Hydrogen-Bonded Organic Frameworks: Current Status and Future Perspectives

Hydrogen-bonded organic frameworks (HOFs), self-assembled from organic or metalated organic building blocks (also termed as tectons) by hydrogen bonding, π-π stacking, and other intermolecular interactions, have become an emerging class of multifunctional porous materials. So far, a library of HOFs with high porosity has been synthesized based on versatile tectons and supramolecular synthons. Benefiting from the flexibility and reversibility of H-bonds, HOFs feature high structural flexibility, mild synthetic reaction, excellent solution processability, facile healing, easy regeneration, and good recyclability. However, the flexible and reversible nature of H-bonds makes most HOFs suffer from poor structural designability and low framework stability. In this Outlook, we first describe the development and structural features of HOFs and summarize the design principles of HOFs and strategies to enhance their stability. Second, we highlight the state-of-the-art development of HOFs for diverse applications, including gas storage and separation, heterogeneous catalysis, biological applications, sensing, proton conduction, and other applications. Finally, current challenges and future perspectives are discussed.

Exploring Multifunctional Hydrogen-Bonded Organic Framework Materials

Hydrogen-bonded organic framework (HOF) materials have provided a new dimension and bright promise as a new platform for developing multifunctional materials. They can be readily self-assembled from their corresponding organic molecules with diverse functional sites such as carboxylic acid and amine groups for their hydrogen bonding and aromatic ones for their weak π···π interactions to stabilize the frameworks. Compared with those established porous materials such as zeolites, metal-organic frameworks (MOFs), and covalent-organic frameworks (COFs), it is much more difficult to stabilize HOFs and thus establish their permanent porosities given the fact that hydrogen bonds are typically weaker than ionic, coordination, and covalent bonds. But it provides the uniqueness of HOF materials in which they can be easily recovered and regenerated through simple recrystallization. HOF materials can also be easily and straightforwardly processed and very compatible with the biomolecules, making them potentially very useful materials for industrial and biomedical applications. The reversible and weak bonding nature of the hydrogen bonds can be readily utilized to construct flexible porous HOF materials in which we can tune the temperature and pressure to control their porosities and, thus, their diverse applications, for example, on gas separations, gas storage, drug delivery, and sensing. Some specific organic functional groups are quite directional for the hydrogen bond formations; for example, carboxylic acid prefers to form a directional dimer, which has enabled us to readily construct reticular porous HOF materials whose pores can be systematically tuned. In this Account, we outline our journey of exploring this new type of porous material by establishing one of the first porous HOFs in 2011 and thus developing its diverse applications. We have been able to use organic molecules with different functional sites, including 2,4-diaminotriazine (DAT), carboxylic acid (COOH), aldehyde (CHO), and cyano (CN), to construct porous HOFs. Through tuning the pore sizes, introducing specific binding sites, and making use of the framework flexibility, we have realized a series of HOF materials for the gas separations of C₂H₂/C₂H₄, C₂H₄/C₂H₆, C₃H₆/C₃H₈, C₂H₂/CO₂, CO₂/N₂, and Xe/Kr and enantioselective separation of alcohols. To make use of optically active organic molecules, we have developed HOF materials for their luminescent sensing and optical lasing. Our research endeavors on multifunctional HOF materials have initiated extensive research in this emerging research topic among chemistry and materials sciences communities. We foresee that not only many more HOF materials will be developed but novel functions will be fulfilled beyond our imaginations soon.

A Flexible Hydrogen-Bonded Organic Framework Constructed from a Tetrabenzaldehyde with a Carbazole N-H Binding Site for the Highly Selective Recognition and Separation of Acetone

Rational design of hydrogen-bonded organic frameworks (HOFs) with multiple functionalities is highly sought after but challenging. Herein, we report a multifunctional HOF (HOF-FJU-2) built from 4,4',4'',4'''-(9H-carbazole-1,3,6,8-tetrayl)tetrabenzaldehyde molecule with tetrabenzaldeyde for their H bonding interactions and carbazole N-H site for its specific recognition of small molecules. The Lewis acid N-H sites allow HOF-FJU-2 facilely separate acetone from its mixture with another solvent like methanol with smaller pK_a value. The donor (D)-π-acceptor (A) aromatic nature of the organic building molecule endows this HOF with solvent dependent luminescent/chromic properties, so the column acetone/methanol separation on HOF-FJU-2 can be readily visualized.

Tetrazolyl Porphyrin-Based Hydrogen-Bonded Organic Frameworks: Active Sites-Mediated Host-Guest Synergy for Advanced Antimicrobial Applications

Hydrogen-bonded organic frameworks (HOFs) with multiple functions and permanent pores have received widespread attention due to their potential applications in gas adsorption/separation, drug delivery, photocatalysis, proton conduction, and other fields. Herein, we constructed a three-dimensional (3D) HOF with 1D square channels by utilizing a dual-functional tetrazolyl porphyrin ligand bearing an active center of the porphyrin core and open sites of nitrogen atoms through π-π stacking and hydrogen-bonding interaction self-assembly. The structure exhibits both solvent resistance and thermal stability, and especially, maintains these after being transformed into nanoparticles. Meanwhile, the active sites exposed on the inner wall of the pores can interact well with the photoactive cationic dye molecules to form an effective host-guest (H-G) system, which can realize boosted photosensitized singlet oxygen (1O2) production under red light irradiation and synergistic sterilization toward Staphylococcus aureus (S. aureus) with an inhibition ratio as high as 99.9%. This work provides a valuable design concept for HOF-related systems in pursuit of promoted photoactivity.

Coordination-Guided Conformational Locking of 1D Metal-Organic Frameworks for a Tunable Stimuli-Responsive Luminescence Region

One-dimensional (1D) metal-organic frameworks (MOFs) have shown great potential for designing more sensitive and smart stimuli-responsive photoluminescence metal-organic frameworks (PL-MOFs). Herein, we propose a strategy for constructing the 1D MOFs with tunable stimuli-responsive luminescence regions based on coordination-guided conformational locking. Two flexible 1D MOF microcrystals with trans- and cis-coordination modes, respectively, were synthesized by controlling the spatial constraint of solvents. The two 1D frameworks possess different conformation lockings of gain ligands, which have a great influence on the rotating restrictions and corresponding excited-state behaviors, generating the remarkably distinct color-tunable ranges (cyan-blue to green and cyan-blue to yellow, respectively). On this basis, the two 1D MOF materials, benefiting from the varied stimuli-responsive ranges, have displayed great potential in fulfilling the anticounterfeiting and information encryption applications. These results provide valuable guidance for the development of smart MOF-based stimuli-responsive materials in information identification and data encryption.

Solvent-Triggered Fast and Visible Switching between Cage- and Channel-Type Hydrogen-Bonded Organic Frameworks

The inherent weak bonding nature of hydrogen-bonded organic frameworks (HOFs) performs like a double-edged sword in that it endows HOFs with superiority in processability and dynamicity but deactivates its on-demand controllability in the crystalline phase. Herein, based on the synergy of dynamic H-bonding interactions and the tailored low solubility in common organic solvents, reversible and fast topological transitions between cage- and channel-type HOFs were achieved upon immersing in the solution state. The aggregation-induced-emission character of the tecton facilitates the visualization of the elusive initial transition process with high sensitivity. In addition, the visible transition from cage- and channel-type HOFs to thermally stable crystalline phases is also achieved under thermal induction.

Design Rules of Hydrogen-Bonded Organic Frameworks with High Chemical and Thermal Stabilities

Hydrogen-bonded organic frameworks (HOFs), self-assembled from strategically pre-designed molecular tectons with complementary hydrogen-bonding patterns, are rapidly evolving into a novel and important class of porous materials. In addition to their common features shared with other functionalized porous materials constructed from modular building blocks, the intrinsically flexible and reversible H-bonding connections endow HOFs with straightforward purification procedures, high crystallinity, solution processability, and recyclability. These unique advantages of HOFs have attracted considerable attention across a broad range of fields, including gas adsorption and separation, catalysis, chemical sensing, and electrical and optical materials. However, the relatively weak H-bonding interactions within HOFs can potentially limit their stability and potential use in further applications. To that end, this Perspective highlights recent advances in the development of chemically and thermally robust HOF materials and systematically discusses relevant design rules and synthesis strategies to access highly stable HOFs.

Tunable Fluorescence in Two-Component Hydrogen-Bonded Organic Frameworks Based on Energy Transfer

A dumbbell-shaped compound (TPAD) with four 2,4-diaminotriazine moieties as H-bond units and a benzene ring as a bridge group was found to form hydrogen-bonded organic frameworks (HOFs) with strong cyan fluorescence. An energy acceptor, 6,6',6″,6‴-(((benzo[c][1,2,5]thiadiazole-4,7-diylbis-(4,1-phenylene))bis(azanetriyl))tetrakis(benzene-4,1-diyl))tetrakis(1,3,5-triazine-2,4-diamine) (BTAD), with the same molecular skeleton as TPAD and a longer emission wavelength could homogeneously distribute within the framework of TPAD through occupying the locations of TPAD. As a result, two-component HOFs (TC-HOFs) were formed. The nonradiative energy transfer from TPAD as the donor to BTAD as the acceptor happens within frameworks owing to the efficient spectral overlap between the emission of TPAD and the absorption of BTAD. Moreover, the emission wavelengths and colors of TC-HOFs could be easily and continuously modulated by the content of the acceptor. The fluorescence color changed from cyan to orange when the content of BTAD gradually increased. This finding affirms that TC-HOFs with continuously adjustable composition can be constructed from two molecules with the same molecular skeleton, and highly efficient nonradiative energy transfer may happen in porous TC-HOFs. To the best of our knowledge, these TC-HOFs are the first example of TC-HOFs involved in energy transfer.

Robust Mesoporous Functional Hydrogen-Bonded Organic Framework for Hypochlorite Detection

Although tremendous progress has been achieved in the field of hydrogen-bonded organic frameworks (HOFs), the low stability, small/none pores, and difficult functionality severely obstruct their development. Herein, a novel robust mesoporous HOF (HOF-FAFU-1) decorated with a high density of free hydroxy moieties has been designed and readily synthesized in the de novo synthesis. In HOF-FAFU-1, the planar building blocks are connected to each other by typical intermolecular carboxylate dimers to form two-dimensional (2D) layers with sql topology, which are further connected to their adjacent layers by face-to-face π-π interactions to obtain a three-dimensional (3D) open mesoporous framework. Owing to the high density of intermolecular hydrogen bonding and strong π-π interactions, HOF-FAFU-1 is very stable, allowing it to retain its structure in aqueous solutions with a pH range of 1-9. Benefiting from the decorated hydroxy moieties, HOF-FAFU-1 was exploited as a fluorescent sensor for hypochlorite detection in water media by a turn-off mode, which cannot be realized by its nonhydroxy groups anchoring counterpart (HOF-TCBP). The proposed sensing system is highly efficient, validated by a very broad linear range (0-0.45 mM), fast response (15 s), and small limit of detection (LOD) (1.32 μM). The fluorescent quenching of HOF-FAFU-1 toward hypochlorite was also investigated, mainly being ascribed to the transformation of building blocks from the fluorescent reduced state to the nonfluorescent oxidative state. This work not only demonstrates that HOFs integrated with high stability and large pores as well as high density of functional groups can be simultaneously realized by judicious design of building blocks but also conceptually elucidates that such HOFs can effectively extend the application fields of HOFs.

Framework-Shrinkage-Induced Wavelength-Switchable Lasing from a Single Hydrogen-Bonded Organic Framework Microcrystal

Porous organic materials (POMs) have shown great potential for fabricating tunable miniaturized lasers. However, most pure-POM micro/nanolasers are achieved via coordination interactions, during which strong charge exchanges inevitably destroy the intrinsic gain property and even lead to optical quenching, hindering their practical applications. Herein, we reported on an approach to realize hydrogen-bonded organic framework (HOF)-based in situ wavelength-switchable lasing based on the framework-shrinkage effect. A flexible HOF with reversible framework shrinkage was constructed from gain blocks with multiple rotors. The framework shrinkage of the HOF induced the in situ regulation on the conformation and conjugation degree of gain blocks, leading to distinct energy-level structures with blue/green-color gain emissions. Inspired by this, the in situ wavelength-switchable lasing from HOF microcrystals was achieved through reversibly controlling the framework shrinkage via the absorption/desorption of guests. The results offer useful insight into the use of flexible HOFs for exploiting miniaturized lasers with on-demand nanophotonics performance.

Functionalization of a stable AIE-based hydrogen-bonded organic framework for white light-emitting diodes

Hydrogen-bonded organic frameworks (HOFs) have received tremendous attention in recent years due to the good designability. However, the pure organic nature of HOFs sometimes limits the application development and performance improvement. Functionalizing is an effective strategy to control and modulate material properties, which can achieve properties that cannot be achieved by a pristine material. Herein, a series of HOF-76⊃DSMI were synthesized through functionalizing the stable AIE-based HOF-76 by incorporating a red dye which complements the deficiency of the red component of HOF-76. Then, a single matrix white light-emitting diode (WLED) was fabricated by coating the HOF-76⊃DSMI material on a 460 nm blue LED with CIE chromaticity coordinates of (0.333, 0.329), a correlated colour temperature (CCT) of 5490 K and a colour rendering index (CRI) of 80.

We successfully fabricated a white light-emitting diode by coating functionalized AIE-based HOF-76 material on a 460 nm blue LED chip.

Luminescent organic porous crystals from non-cyclic molecules and their applications

Organic porous crystals from small and non-cyclic organic molecules can be constructed by various intermolecular weak interactions. Owing to their precise stacking types, intermolecular interaction and pore microstructure, the relationship...