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J Am Chem Soc
J Am Chem Soc
ja
jacsat
Journal of the American Chemical Society
0002-7863
1520-5126
American Chemical Society

39225332
10.1021/jacs.4c05812
Article
Aggregation Induced Emission-Based Covalent Organic Frameworks for High-Performance Optical Wireless Communication
https://orcid.org/0000-0001-9908-4221
Jindal Swati †⊥
https://orcid.org/0000-0002-7838-5575
Wang Jian-Xin †⊥
https://orcid.org/0000-0002-8378-6429
Wang Yue ‡
Thomas Simil †
Mallick Arijit †
Bonneau Mickaele †
Bhatt Prashant M. †
https://orcid.org/0000-0001-6247-842X
Alkhazragi Omar ‡
Nadinov Issatay †
https://orcid.org/0000-0002-1480-6975
Ng Tien Khee ‡
https://orcid.org/0000-0003-1861-9226
Shekhah Osama †
https://orcid.org/0000-0001-5029-2142
Alshareef Husam N. §
Ooi Boon S. *‡
https://orcid.org/0000-0001-8500-1130
Mohammed Omar F. *†∥
https://orcid.org/0000-0003-1916-9837
Eddaoudi Mohamed *†
† Advanced Membranes and Porous Materials Center, Division of Physical Science and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
‡ Photonics Laboratory, Division of Computer, Electrical, and Mathematical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
§ Materials Science and Engineering, Physical Science and Engineering Division, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
∥ KAUST Catalysis Center, Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
* Email: boon.ooi@kaust.edu.sa.
* Email: omar.abdelsaboor@kaust.edu.sa.
* Email: mohamed.eddaoudi@kaust.edu.sa.
03 09 2024
18 09 2024
146 37 2553625543
28 04 2024
28 06 2024
26 06 2024
© 2024 The Authors. Published by American Chemical Society
2024
The Authors
https://creativecommons.org/licenses/by-nc-nd/4.0/ Permits non-commercial access and re-use, provided that author attribution and integrity are maintained; but does not permit creation of adaptations or other derivative works (https://creativecommons.org/licenses/by-nc-nd/4.0/).

Here, we report the first utilization of covalent organic frameworks (COFs) in optical wireless communication (OWC) applications. In the solid form, aggregation-induced emission (AIE) luminogen often shows promising emissive characteristics that augment radiative decays and improve fluorescence. We have synthesized an AIE-COF through the Knoevenagel condensation reaction by taking advantage of the ability to carefully design and alter the COF structure by integrating an AIE luminogen with linear building blocks. The synthesized AIE-COF exhibited a high solid-state photoluminescence quantum yield (∼39%) and a short photoluminescence lifetime (∼1 ns), crucial for achieving modulation bandwidth for high-speed OWC applications. For comparison, we constructed an aggregation-caused quenching based COF, showing a similar lifetime but almost insignificant quantum yield. The orthogonal frequency-division multiplexing modulation strategy employed by the AIE-COF demonstrates remarkable high-rate data transmission, with a wide −3 dB modulation bandwidth of nearly 200 MHz and achieving high net data rates of 825 Mb/s, outperforming traditional materials. These results open new avenues for the ability to design and finetune new COF materials for their utilization as color converters in developing cutting-edge OWC components, enabling faster and more efficient data transfer.

King Abdullah University of Science and Technology 10.13039/501100004052 NA document-id-old-9ja4c05812
document-id-new-14ja4c05812
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pmcIntroduction

Nowadays, optical wireless communication (OWC) technology is significantly advancing high-speed data transmission by harnessing the ultraviolet (UV)–visible–near-infrared light spectrum, facilitating faster and more secure data transfer compared to conventional radio frequency communication.1,2 OWC has the transformative potential to redefine our approach to Internet connectivity with its broad license-free bandwidth, diminished electromagnetic interference, and improved security. It can enable applications for both indoor and outdoor sectors such as light-fidelity, underwater, vehicle-to-vehicle, satellite communication, healthcare, defense, and aviation, etc.3−12 Traditional approaches to OWC have relied on inorganic materials, such as ceramics or perovskites, for color-converting phosphors to improve data transfer rates.13−22 However, these materials present challenges, including harsh synthesis conditions, high fabrication costs, and environmental concerns due to the use of heavy metals, limiting their commercial viability.14,18−22

In response to these limitations, hybrid organic/inorganic materials, particularly metal–organic frameworks (MOFs), have emerged as promising alternatives. MOFs are typically constructed from the combination of inorganic metal ions/clusters and organic multidentate ligands to form targeted structures.23,24 MOFs possess unique properties such as design flexibility, structural and functional tunability, and specific optical and photoluminescence (PL) characteristics and have been explored as excellent candidates as color converters for OWC applications.25−27 The systematic modulation of fluorescent organic linkers and metal clusters in MOFs has led to a tunable modulation bandwidth ranging from 62.1 to 150.0 MHz and a net data rate from ∼303 to ∼363 Mb/s.27 These promising results have paved the way for further exploration of fluorescent materials to construct high-performance, energy-efficient, and secure data communication systems.

Organic-based fluorescent materials exhibiting high photoluminescence quantum yield (PLQY) play a pivotal role as color converters in the context of OWC that can convert or mix their fluorescence with the excitation light source for visible light data transmission. Furthermore, organic fluorescent materials offer distinct advantages in this domain, such as bright emission, high fluorescence quantum yield, short excited state lifetime, high wavelength tunability, biocompatibility, ease of thin-film fabrication, and integration with smart lighting.28,29 However, organic fluorophores exhibiting π–π stacking interactions often experience fluorescence quenching in the concentrated state referring to aggregation-caused quenching (ACQ).30−32 In contrast, aggregation-induced emission (AIE) molecules exhibit promising emissive properties in the solid state due to the restriction of intramolecular rotation (RIR), leading to increased radiative decays and fluorescence enhancement.32,33 AIE-based fluorophores, due to high solid-state fluorescence quantum yield and short luminescent lifetimes, can be integrated into the light-emitting or detecting components of the OWC system to enhance the channel capacity or field of view, thus improving data transmission and reception.29 The unique optical properties of AIE systems hold the potential for achieving more reliable and advanced OWC systems. Recently, AIE systems have been explored for high-speed OWC, which has demonstrated a broad −3 dB modulation bandwidth of ∼110 MHz with a high net data rate of ∼600 Mb/s, which is comparatively very high compared to reported traditional ceramic, inorganic perovskites, organic materials, MOFs, etc.13−15,25−27,34−36 However, a lower conjugated degree of organic fluorophores led to the disintegration of compounds in the presence of light, which makes them susceptible to environmental conditions that hinder their capacity to provide high fluorescence quantum yield and compatibility with light communication systems.

In this context, covalent organic frameworks (COFs)—a subclass of porous materials—consist of solely organic building blocks connected through covalent bonds forming porous, crystalline, and extended conjugated structures.37,38 These versatile materials have applications in various fields, such as drug delivery, small molecule adsorption, energy storage, sensing, gas storage/separation, and catalysis.38−40 Nevertheless, no studies have yet reported the utilization of COFs in OWC technology. By the judicious selection of organic building blocks, the optical and PL properties of COFs can be modified for effective light absorption and emission.38 The tunable characteristics of COFs make them excellent candidates for designing color-converting layers in OWC devices.

This study leverages the unique properties of organic molecules exhibiting AIE phenomenon to construct a two-dimensional AIE-COF via Knoevenagel condensation reaction specifically designed for high-speed OWC applications. Through steady-state and time-resolved spectroscopy measurements and DFT calculations, we confirm the AIE mechanism and characterize the AIE-based COFs, highlighting their high solid-state PLQY and short lifetimes. These properties significantly contribute to their −3 dB modulation bandwidth and net data rate enhancement in OWC applications. The AIE-based COFs demonstrate a broad −3 dB modulation bandwidth approaching 200 MHz and achieve high net data rates of sub-1 Gb/s, surpassing conventional materials by a significant margin, showcasing the remarkable potential of AIE-based COFs in high-speed OWCs.

We investigated the incorporation of AIE-active compounds into AIE-COFs, demonstrating significant advancements in OWC technology. With these changes, our study bridges the gap between molecular and material levels, providing a roadmap for the high-performance, scalable, and effective development of OWC systems. This work widens the prospective uses of advanced luminescent materials as color converters for OWC by laying the foundation for future developments in the field.

Results and Discussion

To achieve a high fluorescent material with a high quantum yield, we have targeted four connecting AIE-based luminogen, i.e., 4′,4‴,4′′′′′,4′′′′′′′-(ethene-1,1,2,2-tetrayl)tetrakis(([1,1′-biphenyl]-4-carbaldehyde)) (ETBC).41 Furthermore, 2, 2′-(1,4-phenylene)diacetonitrile (PDAN) was chosen as a linear building block to form sp2 C=C bonds with ETBC monomer. Hence, in a 20 mL Pyrex tube, monomers ETBC and PDAN were subjected to a typical Knoevenagel condensation reaction in the presence of 1,4-dioxane (1.0 mL) as a solvent and sodium methoxide (NaOMe; 0.1 mL) as a catalyst at 120 °C for 72 h to form an extended conjugated AIE-COF structure (Figure 1). For comparison, we have synthesized an ACQ-COF using a planar four-connecting organic linker, i.e., 4,4′,4″,4‴-([9,9′-bicarbazole]-3,3′,6,6′-tetrayl)tetrabenzaldehyde (BCTB).42 To connect the latter into an extended COF structure, we chose p-phenylenediamine (PD) as a monomer, which was subjected to a condensation reaction in a 20 mL Pyrex tube in the presence of o-dichlorobenzene (1.0 mL), butanol (1.0 mL), and a catalytic amount of acetic acid (6 M AcOH; 0.05 mL) at 120 °C for 72 h, led to the formation of imine-linked ACQ-COF (Figure 1).42 The optical images of AIE- and ACQ-COF show the difference between the optical properties of both COFs (Figure 1).

Figure 1 Synthetic scheme of AIE-COF and ACQ-COF. The optical images of the COFs are shown in the insets of the corresponding chemical structure.

Powder X-ray diffraction (PXRD) measurements were conducted to assess the crystalline behavior of both COFs. AIE-COF displays 2θ peaks at 3.64°, corresponding to Bragg’s diffraction from the (110) plane, and a broad band at 19.1° represents diffraction from the (001) plane (Figure 2a). On the other hand, ACQ-COF exhibits intense 2θ peaks at 3.37°, along with moderately intense peaks at 6.72 and 10.04°, corresponding to (110), (210), and (310) Bragg’s planes, respectively (Figure 2a). Structural models of the AIE-COF and ACQ-COF framework were generated for both eclipsed (AA) and staggered (AB) conformations using Materials Studio software (Figures S1 and S2). The experimental PXRD pattern of AIE-COF matches reasonably well with the simulated eclipsed AA stacking models (Figure 2), confirming the formation of kgm lattice with primitive (P1) space group. The optimized unit cell parameters are found to be a = 55.7756 Å, b = 55.7617 Å, c = 3.9376 Å, α = 86.8627°, β = 84.3259°, γ = 120.0386° (Figures 2a and S1). Similarly the PXRD pattern of the ACQ-COF matches reasonably well with the eclipsed model, also exhibiting a primitive (P1) space group. The optimized cell parameters for the ACQ-COF are determined to be a = 26.2578 Å, b = 26.2578 Å, c = 3.6162 Å, α = 90.584°, β = 85.882°, γ = 93.342° corresponds to sql topology (Figures 2a and S2).

Figure 2 (a) PXRD pattern of simulated structures with different eclipsed (AA) and staggered (AB) conformations and experimental structures of AIE-COF (orange) and ACQ-COF (blue). (b) FT-IR spectra of AIE-COF (orange), ETBC (dark blue), PDAN (green), ACQ-COF (blue), BCTB (violet), and PD (pink). (c) 13C solid-state CP-MAS NMR spectra of AIE-COF (orange) and ACQ-COF (blue).

The chemical composition of both the COFs was confirmed by Fourier transform infrared (FT-IR) spectroscopy. In the case of AIE-COF, the appearance of the C=C stretching band around 1480 cm–1 and the shift in the stretching frequency of the nitrile group (C≡N) from 2249 to 2213 cm–1 compared to monomer ETBC confirm the formation of COF (Figure 2b). Additionally, the stretching frequency corresponding to C–H and C=O in the –CHO functionalities in the ETBC monomer appearing at 2725 and 1692 cm–1, respectively, was found to have disappeared in the respective AIE-COF structure. Similarly, the characteristic frequency corresponding to the imine bond C=NH at 1603 cm–1 for the ACQ-COF confirms the formation of imine COF. Additionally, the solid-state 13C cross-polarization magic angle spinning (CP-MAS) NMR spectra of both AIE-COF and ACQ-COF featured broad signals around 127.5 and 126.3 ppm, respectively, corresponding to aromatic carbons of benzene rings (Figure 2c). Furthermore, the 13C signals corresponding to C≡N and C=N functionalities showed shoulder peaks at 117.3 and 154.9 ppm, respectively, unambiguously establishing the formation of both COFs (Figure 2c).

Scanning electron microscopy (SEM) was used to study the morphology of the materials. It revealed that the AIE-COF exhibited a tightly packed layered structure with layer slippage, while the ACQ-COF showed the formation of uniformly distributed loosened aggregates (Figure S3). Nitrogen sorption isotherms for both AIE- and ACQ-COF were measured at 77 K to determine the porosity of both structures. Brunauer–Emmett–Teller surface identification (BETSI) was determined from the nitrogen adsorption isotherm collected at 77 K by applying the BETSI algorithm.43 The BETSI for AIE-COF was estimated to be 106 m2/g (Figure S4). The pores size distributions (PSD) plot, computed using quenched solid density functional theory (QSDFT), revealed mesopores (4.8 nm) and micropores (1.3 nm) in reasonable agreement with the simulated eclipsed structure of AA stacking model for kg m topology (Figure S5). The pore volume was relatively low, indicating layer slippage, consistent with the SEM images (Figure S3). For the ACQ-COF, the BETSI was significantly higher at 1364 m2/g (Figure S6). Mesopores (2.2 nm) were observed in the PSD derived from the QSDFT, consistent with the underlying sql topology’s eclipsed (AA) stacking model in the simulated structure (Figure S7). The calculated pore volume at P/P0 = 0.99 was 0.72 cm3/g. Later, thermogravimetric analysis (TGA) under nitrogen atmosphere revealed the thermal stability of both COFs up to 400 °C (Figure S8).

The facile manipulation of the structural characteristics of COF materials provides a convenient means to exert precise control over their photophysical properties. This control is achieved by skillfully manipulating the luminescent attributes of organic ligands. Notably, the incorporation of the AIE group leads to a substantial increase in luminescence intensity, exceeding that achieved with the use of ACQ counterparts several dozen times. This enhancement in luminescence intensity holds significant implications for the data transmission rate of COF materials in OWC applications. Moreover, the inherent short PL lifetime (τ) of the corresponding organic ligands persists even after polymerization into COF materials. This enduring short PL lifetime proves advantageous for enhancing the −3 dB bandwidth of COF materials in OWC applications. The enhanced luminescence intensity and abbreviated PL lifetime contribute to considerable signal-to-noise ratio (SNR) and rapid modulation, ultimately improving the overall efficiency and performance of COF-based systems in OWC. Thus, the strategic incorporation of AIE groups and the persistence of short luminescence lifetimes in COF materials open promising avenues for advancing their capabilities in OWC applications.

To enable their practical usage, AIE- and ACQ-COFs were strategically incorporated into a poly(methyl methacrylate) (PMMA) polymer matrix.27 The thin film was prepared using the drop-casting method. The slow evaporation rate was employed to minimize film nonuniformity. The morphology of the thin film significantly affects the PL performance, as poor morphology can cause strong light scattering. Figures 3a and S9 illustrate the comparable excitation and emission spectra of both AIE- and ACQ-COFs. These spectra reveal a wide-ranging excitation band spanning from UV to the blue spectral region, accompanied by robust emission bands ranging from 400 to 700 nm and centered at 550 and 480 nm, respectively. Notably, the minimal overlap between their excitation and emission spectra is crucial, laying the foundation for high-performance OWC color-converting converters. We conducted time-correlated single-photon counting experiments to measure the PL lifetimes of both AIE- and ACQ-COFs under 405 nm excitation. The decay curves of each material were fitted using two exponential components (Figure 3b). The average PL lifetime (τavg) was estimated to be approximately 1 ns [τ1 = 0.63 ns (79.5%); τ2 = 2.37 ns (20.5%)] for the AIE-COF and 0.3 ns [τ1 = 0.28 ns (90.6%); τ2 = 1.54 ns (9.4%)] for the ACQ-COF. The slightly longer lifetime of the AIE-COF suggests a delayed recombination process. This unique characteristic is paramount for achieving a wide modulation bandwidth, a critical requirement for efficient OWC applications, as shown in the equation below.27

Figure 3 (a) Excitation and emission spectra, (b) corresponding PL lifetime, and (c) PLQY measurements of the AIE-COF (orange) and ACQ-COF (blue) doped in PMMA. Relative DFT energies calculated at the ωB97XD/6-31G(d, p) level for the torsion potentials related to the rotation of the adjacent units for (d) ACQ-COF and (e,f) AIE-COF. Dashed lines correspond to thermal energy at room temperature.

Additionally, the AIE-COF exhibits an additional advantage due to the AIE properties of its ligands. The PLQY of the AIE-COF (∼39%) is several times higher than that of the ACQ counterpart (∼1%), making it an exceptionally promising candidate for high-performance OWC color conversion (Figure 3c). Moreover, the AIE monomer is already integrated into the COF structure, resulting in its aggregation. Consequently, the high concentration of COF particles in the neat film further quenches the PLQY, leading to a lower PLQY of 7% in the neat film and 4% in chloroform solution.

The exceptionally lower fluorescence quantum yield for ACQ-COF is attributed to the introduction of flexible single bonds around imine-linkage, which increases the planarity of structure, promoting π–π stacking of the layers, increasing the nonradiative decay channels and subsequently quenching the fluorescence of material in the solid state.44 Furthermore, the calculated radiative rates for AIE-COF and ACQ-COF are 3.9 × 108 and 2.9 × 107 s–1, respectively, while their nonradiative rates are 6.1 × 108 and 2.8 × 109 s–1, respectively. This demonstrates that the radiative rate of AIE-COF is significantly higher than that of ACQ-COF, and its nonradiative rate is considerably lower. These findings further highlight the superior PLQY and OWC performance of AIE-COF in comparison to ACQ-COF.

In the case of AIE-COF, the introduction of 1,4-dicyanostyrylbenzene functionality inside the backbone of the COF led to the formation of sp2 C=C bonds, providing more structural rigidity and extended conjugation.45 This moiety acts as an AIE fluorophore; therefore, in solid-state upon aggregation, it will lead to the locking of conformation due to the RIR phenomenon, which restrains all the nonradiative pathways competing with the radiative channels, leading to the fluorescence enhancement of COF. More importantly, significantly enhancing the PLQY of the AIE-COF would greatly boost the data transmission rate in OWC applications.

To validate this assertion, DFT calculations were performed to calculate torsion potentials associated with the rotation of the phenyl group in both ACQ and AIE units of their corresponding monomer and dimers (see Figures S10 and S11). These calculations were conducted at 5° intervals, and the geometries were extracted from periodic DFT calculations (Figure S11). The extracted fragments correspond to the localized regions of the wave function of the valence and conduction band (Figure S10). In the case of the ACQ dimer unit, the torsion potential exhibits increased sharpness around the equilibrium dihedral angle compared to the ACQ monomer (Figure 3d). Meanwhile, the AIE dimer unit exhibits an even sharper torsion potential than the ACQ dimer, leading to the RIR. This restriction diminishes nonradiative pathways, enhancing the PLQY of AIE-COF compared to ACQ-COF (see Figure 3e,f).

To assess the applicability of AIE-based COFs in OWC scenarios, we conducted small-signal frequency response evaluations on both AIE- and ACQ-COFs using the experimental setup depicted in Figure 4a. In the setup, the samples were positioned within an integrating sphere and excited by a 375 nm laser diode. The fluorescence emitted from the samples was then collected and converted into an electric signal by an avalanche photodetector (APD). A vector network analyzer was employed to generate a modulation signal for the laser and process the output signal from APD to calculate the response at each frequency. By subjecting the samples to sinusoidal alternating current signals across a frequency range of 300 kHz to 1 GHz, −3 dB modulation bandwidths of 183.0 MHz for AIE-COF and 258.5 MHz for ACQ-COF were obtained (Figure 4b), which exhibited inverse proportion to their PL lifetime.14 The figure shows that the response of AIE-COF is significantly higher and smoother than that of ACQ-COF. In contrast, the response of ACQ-COF is almost at the noise level due to the low PLQY, making it unusable for high-speed communication. Remarkably, the broad modulation bandwidths exhibited by these COF materials far surpassed those of many commercially available ceramic, perovskite, and organic materials.13−15,25−27,34−36,46 This underscores their immense potential for application in high-speed OWCs. Moreover, these COFs presented distinct advantages over ceramic and perovskite counterparts, including lower economic and synthesis costs, heightened stability and flexibility, and straightforward scalability. These attributes collectively position AIE-based COFs as highly promising candidates for advancing high-speed OWC technology, offering superior performance, economic viability, and practical feasibility.

Figure 4 Optical modulation measurements based on DCO-OFDM (a) experimental small-signal frequency response measurement setup. (b) Frequency response of AIE- and ACQ-COFs. The electrical noise from APD (cutoff ∼ 400 MHz) is highlighted in gray. (c) −3 dB bandwidth and net data rate obtained with AIE- and ACQ-COFs. (d) DCO-OFDM implementation for AIE-COF: (from top to bottom) power loading factor, spectral efficiency, SNR, and BER of each subcarrier.

To further demonstrate the efficacy of these COFs as color-converters in OWC links, we conducted direct current (DC)-biased optical orthogonal frequency-division multiplexing (DCO-OFDM) modulation. As depicted in Figure 4b–d, the AIE-based COF exhibited a remarkable SNR exceeding 20 dB, attributed to its high PLQY. However, the ACQ-COF, characterized by an ultraweak luminescence intensity, recorded almost no discernible signal, although it exhibits a wider bandwidth (Figure 4b). Following signal processing, adaptive power and bit loading were efficiently allocated based on the channel capacity of the AIE-based COF estimated by sending a 4-quadrature amplitude modulation (QAM) test signal, which achieved a high gross data rate of 986 Mb/s. After removing training symbols and 7% overhead for forward error correction, a net data rates rate of 825 Mb/s with corresponding bit error ratios (BER) of 3.7 × 10–3 was achieved.27 It is observed that subcarriers with lower indexes tend to have higher BER due to higher QAM orders and lower power loading in this region. This issue can be improved, and data rates can be increased through further optimizations of power and bit loading schemes. The constellation diagrams are shown in the inset of Figure 4d for various QAM orders in the transmitted signal. These diagrams depict the combination of constellations for all subcarriers of the same QAM order. We also investigated the transmission rate without the AIE-COF color converter by directly shining the laser on the APD. A net data rate of 1.23 Gb/s was obtained, slightly higher than with the color converter. Although the laser can be modulated at higher frequencies, the Si-based APD has higher responsivity in green than in UV, and adding the color converter could also improve the versatility and field of view of the communication system. The successful modulation and transmission of data at high rates, along with the superior SNR, further highlight the potential of AIE-based COFs as fast-acting color converters in OWC applications, promising advancements in high-speed optical communication. Combined with their cost-effective manufacturing, nontoxicity, high stability, and flexibility, the proposed material is well-suited for organic-based flexible optoelectronic devices.11 It also opens new possibilities for applications such as wireless human–machine interactions,12 self-powered sensing,47 and high-resolution X-ray imaging.48

Conclusions

In conclusion, a successful implementation of AIE-based COF materials, achieved through meticulous fine-structure modifications, has significantly advanced high-speed OWC technology. More specifically, incorporating AIE-based functional groups into the COF structure allowed precise adjustments of the PL lifetimes and PLQYs, thereby profoundly impacting the modulation bandwidths and net data rates in OWC applications. Notably, the AIE-based COF material demonstrated substantial achievements, boasting broad modulation bandwidths of ∼200 MHz and high net data rates of 825 Mb/s. These values surpass the capabilities of most conventional color-converting phosphors, underscoring the tremendous potential of AIE-based COFs in propelling high-speed OWCs to new heights. These novel findings not only enhance our understanding of COF materials but also provide versatile components for designing and fabricating innovative OWC color-converting phosphors.

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/jacs.4c05812.Figures S1–S11 represent simulated structures, SEM images, sorption isotherms, TGA graphs, excitation and emission spectra, monomer and dimer models of COFs, additional experimental details for the synthesis of COFs, materials, and methods, including DFT calculation detail (PDF)

Supplementary Material

ja4c05812_si_001.pdf

Author Contributions

⊥ S.J. and J.-X.W. contributed equally to this paper.

The authors declare no competing financial interest.

Acknowledgments

This work was supported by the King Abdullah University of Science and Technology (KAUST).
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References

Matheus L. E. M. ; Vieira A. B. ; Vieira L. F. M. ; Vieira M. A. M. ; Gnawali O. Visible Light Communication: Concepts, Applications and Challenges. IEEE Commun. Surv. Tutorials 2019, 21 , 3204–3237. 10.1109/COMST.2019.2913348.
Bao X. ; Yu G. ; Dai J. ; Zhu X. Li-Fi: Light fidelity-a survey. Wireless Networks 2015, 21 , 1879–1889. 10.1007/s11276-015-0889-0.
Chow C.-W. ; Yeh C.-H. ; Liu Y. Optical Wireless Communications (OWC) - Technologies and Applications. Opto-Electronics and Communications Conference (OECC), 2020; pp 1–3.
Borah D. K. ; Boucouvalas A. C. ; Davis C. C. ; Hranilovic S. ; Yiannopoulos K. A Review of Communication-Oriented Optical Wireless Systems. J. Wireless Commun. Networking 2012, 2012 , 91 10.1186/1687-1499-2012-91.
Tugcu E. ; Yazgan A. ; Albayrak C. ; Turk K. Red-Shift Effect in Multi-Color LEDs based Visible Light Communication. Opt. Commun. 2020, 463 , 125451 10.1016/j.optcom.2020.125451.
Li T. ; An C. ; Tian Z. ; Campbell A. T. ; Zhou X. Human Sensing Using Visible Light Communication. Proceedings of the 21st Annual International Conference on Mobile Computing and Networking, 2015; pp 331–344.
Haas H. Li-Fi is A Paradigm-Shifting 5G Technology. Rev. Phys. 2018, 3 , 26–31. 10.1016/j.revip.2017.10.001.
Zheng F. ; Chen Z. ; Li J. ; Wu R. ; Zhang B. ; Nie G. ; Xie Z. ; Zhang H. A Highly Sensitive CRISPR-Empowered Surface Plasmon Resonance Sensor for Diagnosis of Inherited Diseases with Femtomolar-Level Real-Time Quantification. Adv. Sci. 2022, 9 , 2105231 10.1002/advs.202105231.
Chen Z. ; Li J. ; Li T. ; Fan T. ; Meng C. ; Li C. ; Kang J. ; Chai L. ; Hao Y. ; Tang Y. ; Al-Hartomy O. A. ; Wageh S. ; Al-Sehemi A. G. ; Luo Z. ; Yu J. ; Shao Y. ; Li D. ; Feng S. ; Liu W. J. ; He Y. ; Ma X. ; Xie Z. ; Zhang H. A CRISPR/Cas12a-Empowered Surface Plasmon Resonance Platform for Rapid and Specific Diagnosis of the Omicron Variant of SARS-CoV-2. Natl. Sci. Rev. 2022, 9 , 8 10.1093/nsr/nwac104.
Xue T. ; Liang W. ; Li Y. ; Sun Y. ; Xiang Y. ; Zhang Y. ; Dai Z. ; Duo Y. ; Wu L. ; Qi K. ; Shivananju B. N. ; Zhang L. ; Cui X. ; Zhang H. ; Bao Q. Ultrasensitive Detection of miRNA with an Antimonene-based Surface Plasmon Resonance Sensor. Nat. Commun. 2019, 10 , 28 10.1038/s41467-018-07947-8.30604756
Guo K. ; Tang Z. ; Chou X. ; Pan S. ; Wan C. ; Xue T. ; Ding L. ; Wang X. ; Huang J. ; Zhang F. ; Weie B. Printable Organic Light-Emitting Diodes for Next-Generation Visible Light Communications: A Review. Adv. Photonics Nexus 2023, 2 , 044001 10.1117/1.apn.2.4.044001.
Pandey P. ; Thapa K. ; Ojha G. P. ; Seo M.-K. ; Shin K. H. ; Kim S.-W. ; Sohn J. I. Metal-Organic Frameworks-based Triboelectric Nanogenerator Powered Visible Light Communication System for Wireless Human-Machine Interactions. Chem. Eng. J. 2023, 452 , 139209 10.1016/j.cej.2022.139209.
Mei S. ; Liu X. ; Zhang W. ; Liu R. ; Zheng L. ; Guo R. ; Tian P. High-Bandwidth White-Light System Combining a Micro-LED with Perovskite Quantum Dots for Visible Light Communication. ACS Appl. Mater. Interfaces 2018, 10 , 5641–5648. 10.1021/acsami.7b17810.29345894
Kang C. H. ; Wang Y. ; Alkhazragi O. ; Lu H. ; Ng T. K. ; Ooi B. S. Down-Converting Luminescent Optoelectronics and Their Applications. APL Photonics 2023, 8 , 020903 10.1063/5.0127552.
Kang C. H. ; Dursun I. ; Liu G. ; Sinatra L. ; Sun X. ; Kong M. ; Pan J. ; Maity P. ; Ooi E.-N. ; Ng T. K. ; Mohammed O. F. ; Bakr O. M. ; Ooi B. S. High-Speed Colour-Converting Photodetector with All-Inorganic CsPbBr3 Perovskite Nanocrystals for Ultraviolet Light Communication. Light: Sci. Appl. 2019, 8 , 94 10.1038/s41377-019-0204-4.31645937
Martínez J. ; Osorio-Roman I. ; Gualdrón-Reyes A. F. Progress of Organic/Inorganic Luminescent Materials for Optical Wireless Communication Systems. Photonics 2023, 10 , 659 10.3390/photonics10060659.
Minotto A. ; Haigh P. A. ; Łukasiewicz Ł. G. ; Lunedei E. ; Gryko D. T. ; Darwazeh I. ; Cacialli F. Visible Light Communication with Efficient Far-Red/Near-Infrared Polymer Light-Emitting Diodes. Light: Sci. Appl. 2020, 9 , 70 10.1038/s41377-020-0314-z.32351694
Wang Z. ; Wei Z. ; Cai Y. ; Wang L. ; Li M. ; Liu P. ; Xie R. ; Wang L. ; Wei G. ; Fu H. Y. Encapsulation-Enabled Perovskite-PMMA Films Combining a Micro-LED for High-Speed White-Light Communication. ACS Appl. Mater. Interfaces 2021, 13 , 54143–54151. 10.1021/acsami.1c15873.34747607
Zhu S. ; Shan X. ; Lin R. ; Qiu P. ; Wang Z. ; Lu X. ; Yan L. ; Cui X. ; Zhang G. ; Tian P. Characteristics of GaN-on-Si GreenMicro-LED for Wide Color Gamut Display and High-Speed Visible Light Communication. ACS Photonics 2023, 10 , 92–100. 10.1021/acsphotonics.2c01028.
Kong D. ; Zhou Y. ; Chai J. ; Chen S. ; Chen L. ; Li L. ; Lin T. ; Wang W. ; Li G. Recent Progress in InGaN-based Photodetectors for Visible Light Communication. J. Mater. Chem. C 2022, 10 , 14080–14090. 10.1039/D2TC02122F.
Zhang Y. ; Shen W. ; Wu S. ; Tang W. ; Shu Y. ; Ma K. ; Zhang B. ; Zhou P. ; Wang S. High-Speed Transition-Metal Dichalcogenides Based Schottky Photodiodes for Visible and Infrared Light Communication. ACS Nano 2022, 16 , 19187–19198. 10.1021/acsnano.2c08394.36305492
Chen S.-W. H. ; Huang Y.-M. ; Chang Y.-H. ; Lin Y. ; Liou F.-J. ; Hsu Y.-C. ; Song J. ; Choi J. ; Chow C.-W. ; Lin C.-C. ; Horng R.-H. ; Chen Z. ; Han J. ; Wu T. ; Kuo H.-C. High-Bandwidth Green Semipolar (20–21) InGaN/GaN Micro Light-Emitting Diodes for Visible Light Communication. ACS Photonics 2020, 7 , 2228–2235. 10.1021/acsphotonics.0c00764.
Furukawa H. ; Cordova K. E. ; O’Keeffe M. ; Yaghi O. M. The Chemistry and Applications of Metal-Organic Frameworks. Science 2013, 341 , 1230444 10.1126/science.1230444.23990564
Allendorf M. D. ; Bauer C. A. ; Bhakta R. K. ; Houk R. J. T. Luminescent Metal-Organic Frameworks. Chem. Soc. Rev. 2009, 38 , 1330–1352. 10.1039/b802352m.19384441
Wang Z. ; Wang Z. ; Lin B. ; Hu X. F. ; Wei Y. F. ; Zhang C. ; An B. ; Wang C. ; Lin W. Warm-White-Light-Emitting Diode Based on a Dye-Loaded Metal–Organic Framework for Fast White-Light Communication. ACS Appl. Mater. Interfaces 2017, 9 , 35253–35259. 10.1021/acsami.7b11277.28920667
Wang J.-X. ; Wang Y. ; Nadinov I. ; Yin J. ; Gutiérrez-Arzaluz L. ; Healing G. ; Alkhazragi O. ; Cheng Y. ; Jia J. ; Alsadun N. ; Kale V. S. ; Kang C. H. ; Ng T. K. ; Shekhah O. ; Alshareef H. N. ; Bakr O. M. ; Eddaoudi M. ; Ooi B. S. ; Mohammed O. F. Metal-Organic Frameworks in Mixed-Matrix Membranes for High-Speed Visible-Light Communication. J. Am. Chem. Soc. 2022, 144 , 6813–6820. 10.1021/jacs.2c00483.35412323
Wang J.-X. ; Wang Y. ; Almalki M. ; Yin J. ; Shekhah O. ; Jia J. ; Gutiérrez-Arzaluz L. ; Cheng Y. ; Alkhazragi O. ; Maka V. K. ; Ng T. K. ; Bakr O. M. ; Ooi B. S. ; Eddaoudi M. ; Mohammed O. F. Engineering Metal–Organic Frameworks with Tunable Colors for High-Performance Wireless Communication. J. Am. Chem. Soc. 2023, 145 , 15435–15442. 10.1021/jacs.3c03672.37421307
Khan L. U. Visible Light Communication: Applications, Architecture, Standardization and Research Challenges. Digital Commun. Networks 2017, 3 , 78–88. 10.1016/j.dcan.2016.07.004.
Zhang Y. ; Jiang M. ; Han T. ; Xiao X. ; Chen W. ; Wang L. ; Wong K. S. ; Wang R. ; Wang K. ; Tang B. Z. ; Wu K. Aggregation-Induced Emission Luminogens as Color Converters for Visible-Light Communication. ACS Appl. Mater. Interfaces 2018, 10 , 34418–34426. 10.1021/acsami.8b05950.30205004
Mei J. ; Hong Y. ; Lam J. W. Y. ; Qin A. ; Tang Y. ; Tang B. Z. Aggregation-Induced Emission: The Whole Is More Brilliant than the Parts. Adv. Mater. 2014, 26 , 5429–5479. 10.1002/adma.201401356.24975272
Mei J. ; Leung N. L. C. ; Kwok R. T. K. ; Lam J. W. Y. ; Tang B. Z. Aggregation-Induced Emission: Together We Shine, United We Soar. Chem. Rev. 2015, 115 , 11718–11940. 10.1021/acs.chemrev.5b00263.26492387
Hong Y. ; Lam J. W. Y. ; Tang B. Z. Aggregation-Induced Emission. Chem. Soc. Rev. 2011, 40 , 5361–5388. 10.1039/c1cs15113d.21799992
Wang H. ; Zhao E. ; Lam J. W. Y. ; Tang B. Z. AIE Luminogens: Emission Brightened by Aggregation. Mater. Today 2015, 18 , 365–377. 10.1016/j.mattod.2015.03.004.
Wang J.-X. ; Wang Y. ; Nadinov I. ; Yin J. ; Gutiérrez-Arzaluz L. ; Alkhazragi O. ; He T. ; Ng T. K. ; Eddaoudi M. ; Alshareef H. N. ; Bakr O. M. ; Ooi B. S. ; Mohammed O. F. Aggregation-Induced Fluorescence Enhancement for Efficient X-ray Imaging Scintillators and High-Speed Optical Wireless Communication. ACS Mater. Lett. 2022, 4 , 1668–1675. 10.1021/acsmaterialslett.2c00498.
Vithanage D. A. ; Manousiadis P. P. ; Sajjad M. T. ; Rajbhandari S. ; Chun H. ; Orofino C. ; Cortizo-Lacalle D. ; Kanibolotsky A. L. ; Faulkner G. ; Findlay N. J. ; O’Brien D. C. ; Skabara P. J. ; Samuel I. D. W. ; Turnbull G. A. BODIPY star-shaped molecules as solid state colour converters for visible light communications. Appl. Phys. Lett. 2016, 109 , 013302 10.1063/1.4953789.
Sajjad M. T. ; Manousiadis P. P. ; Orofino C. ; Kanibolotsky A. L. ; Findlay N. J. ; Rajbhandari S. ; Vithanage D. A. ; Chun H. ; Faulkner G. E. ; O’Brien D. C. ; Skabara P. J. ; Turnbull G. A. ; Samuel I. D. W. A Saturated Red Color Converter for Visible Light Communication using a Blend of Star-Shaped Organic Semiconductors. Appl. Phys. Lett. 2017, 110 , 013302 10.1063/1.4971823.
Lohse M. S. ; Bein T. Covalent Organic Frameworks: Structures, Synthesis, and Applications. Adv. Funct. Mater. 2018, 28 , 1705553 10.1002/adfm.201705553.
Haug W. K. ; Moscarello E. M. ; Wolfson E. R. ; McGrier P. L. The Luminescent and Photophysical Properties of Covalent Organic Frameworks. Chem. Soc. Rev. 2020, 49 , 839–864. 10.1039/C9CS00807A.31957763
Parvatkar P. T. ; Kandambeth S. ; Shaikh A. C. ; Nadinov I. ; Yin J. ; Kale V. S. ; Healing G. ; Emwas A.-H. ; Shekhah O. ; Alshareef H. N. ; Mohammed O. F. ; Eddaoudi M. A Tailored COF for Visible-Light Photosynthesis of 2,3-Dihydrobenzofurans. J. Am. Chem. Soc. 2023, 145 , 5074–5082. 10.1021/jacs.2c10471.36827417
Zou G. ; Tian Z. ; Kale V. S. ; Wang W. ; Kandembeth S. ; Cao Z. ; Guo J. ; Czaban-Jóźwiak J. ; Cavallo L. ; Shekhah O. ; Eddaoudi M. ; Alshareef H. N. A Symmetric Aqueous Magnesium Ion Supercapattery Based on Covalent Organic Frameworks. Adv. Energy Mater. 2023, 13 , 2203193 10.1002/aenm.202203193.
Zhao Z. ; Lamb J. W. Y. ; Tang Z. Tetraphenylethene: A Versatile AIE Building Block for the Construction of Efficient Luminescent Materials for Organic Light-Emitting Diodes. J. Mater. Chem. 2012, 22 , 23726 10.1039/c2jm31949g.
EL-Mahdy A. F. M. ; Laia M.-Y. ; Kuo S.-W. A Highly Fluorescent Covalent Organic Framework as a Hydrogen Chloride Sensor: Roles of Schiff Base Bonding and π-Stacking. J. Mater. Chem. C 2020, 8 , 9520–9528. 10.1039/d0tc01872d.
Osterrieth J. W. M. ; Rampersad J. ; Madden D. ; Rampal N. ; Skoric L. ; Connolly B. ; Allendorf M. D. ; Stavila V. ; Snider J. L. ; Ameloot R. ; Marreiros J. ; Ania C. ; Azevedo D. ; Vilarrasa-Garcia E. ; Santos B. F. ; Bu X. H. ; Chang Z. ; Bunzen H. ; Champness N. R. ; Griffin S. L. ; Chen B. L. ; Lin R. B. ; Coasne B. ; Cohen S. ; Moreton J. C. ; Colon Y. J. ; Chen L. J. ; Clowes R. ; Coudert F. X. ; Cui Y. ; Hou B. ; D’Alessandro D. M. ; Doheny P. W. ; Dinca M. ; Sun C. Y. ; Doonan C. ; Huxley M. T. ; Evans J. D. ; Falcaro P. ; Ricco R. ; Farha O. ; Idrees K. B. ; Islamoglu T. ; Feng P. Y. ; Yang H. J. ; Forgan R. S. ; Bara D. ; Furukawa S. ; Sanchez E. ; Gascon J. ; Telalovic S. ; Ghosh S. K. ; Mukherjee S. ; Hill M. R. ; Sadiq M. M. ; Horcajada P. ; Salcedo-Abraira P. ; Kaneko K. ; Kukobat R. ; Kenvin J. ; Keskin S. ; Kitagawa S. ; Otake K. I. ; Lively R. P. ; DeWitt S. J. A. ; Llewellyn P. ; Lotsch B. V. ; Emmerling S. T. ; Putz A. M. ; Marti-Gastaldo C. ; Padial N. M. ; Garcia-Martinez J. ; Linares N. ; Maspoch D. ; del Pino J. A. S. ; Moghadam P. ; Oktavian R. ; Morris R. E. ; Wheatley P. S. ; Navarro J. ; Petit C. ; Danaci D. ; Rosseinsky M. J. ; Katsoulidis A. P. ; Schroder M. ; Han X. ; Yang S. H. ; Serre C. ; Mouchaham G. ; Sholl D. S. ; Thyagarajan R. ; Siderius D. ; Snurr R. Q. ; Goncalves R. B. ; Telfer S. ; Lee S. J. ; Ting V. P. ; Rowlandson J. L. ; Uemura T. ; Liyuka T. ; van derVeen M. A. ; Rega D. ; Van Speybroeck V. ; Rogge S. M. J. ; Lamaire A. ; Walton K. S. ; Bingel L. W. ; Wuttke S. ; Andreo J. ; Yaghi O. ; Zhang B. ; Yavuz C. T. ; Nguyen T. S. ; Zamora F. ; Montoro C. ; Zhou H. C. ; Kirchon A. ; Fairen-Jimenez D. How Reproducible are Surface Areas Calculated from the BET Equation?. Adv. Mater. 2022, 34 , 2201502 10.1002/adma.202201502.
Qian Y. ; Li J. ; Ji M. ; Li J. ; Ma D. ; Liu A. ; Zhao Y. ; Yang C. Fluorescent Covalent Organic Frameworks: A Promising Material Platform for Explosive Sensing. Front. Chem. 2022, 10 , 943813 10.3389/fchem.2022.943813.35910724
Chang C.-W. ; Bhongale C. J. ; Lee C.-S. ; Huang W.-K. ; Hsu C.-S. ; Diau E. W.-G. Relaxation Dynamics and Structural Characterization of Organic Nanobelts with Aggregation-Induced Emission. J. Phys. Chem. C 2012, 116 , 15146–15154. 10.1021/jp304117n.
Zhao J. ; Cheng Y. ; Cheng Z. Design of a Photo-Excited Switchable Broadband Reflective Linear Polarization Conversion Metasurface for Terahertz Waves. IEEE Photonics J. 2018, 10 , 1–10. 10.1109/JPHOT.2018.2792444.
Rana S. M. S. ; Faruk O. ; Islam M. R. ; Yasmin T. ; Zaman K. ; Wang Z. L. Recent Advances in Metal-Organic Framework-Based Self-Powered Sensors: A Promising Energy Harvesting Technology. Coord. Chem. Rev. 2024, 507 , 215741 10.1016/j.ccr.2024.215741.
Wang J.-X. ; Gutiérrez-Arzaluz L. ; Wang X. ; Almalki M. ; Yin J. ; Czaban-Jozwiak J. ; Shekhah O. ; Zhang Y. ; Bakr O. M. ; Eddaoudi M. ; Mohammed O. F. Nearly 100% Energy Transfer at the Interface of Metal-Organic Frameworks for X-ray Imaging Scintillators. Matter 2022, 5 , 253–265. 10.1016/j.matt.2021.11.012.
