Preparation method of a metalized chiral COF and application thereof in electrochemical circular polarization detection

Abstract

The application discloses a preparation method of a metalized chiral COF and application of the metalized chiral COF in electrochemical circular polarization light detection, and the preparation method of the metalized chiral COF comprises the following steps: taking 1,3,5-triformylphloroglucinol, trimethylaniline, a chiral inducer and 2,2'-bipyridine-5,5'-diamine as raw materials, and synthesizing a chiral COF through a solvothermal reaction; then, a coordination reaction is carried out with a metal salt in an alcohol solvent to obtain a metalized chiral COF material; the metalized chiral COF material is used as a photoanode material, spin polarization induced by circular polarization light (CPL) is coupled with a spin-selective oxygen evolution reaction (OER), and a nonlinear characteristic of OER reaction kinetics is used to amplify a micro-spin signal; the material has excellent photoelectric current anisotropy factor (g Iph ) and stability, and solves the problem of low sensitivity of an existing solid-state CPL detector.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials and optoelectronic sensing technology, and relates to a method for preparing metallized chiral COF and its application in electrochemical circularly polarized light detection. Background Technology

[0002] Circularly polarized light (CPL) detection has significant applications in quantum computing, 3D displays, biosensing, and spin optoelectronics. Current CPL detectors are mostly based on traditional solid-state semiconductor materials or chiral organic molecules, and their working principle primarily relies on the differential absorption of left-handed and right-handed CPL (i.e., circular dichroism). However, this direct photo-to-electric conversion mode lacks a signal gain mechanism, leading to an anisotropy factor (g) in the generated photocurrent. Iph The value is usually low (generally less than 0.1), making it difficult to meet the requirements of high-sensitivity detection.

[0003] Covalent organic frameworks (COFs), a class of crystalline porous polymers formed by strong covalent bonds connecting lightweight elements (C, H, O, N, etc.), have become star materials in the field of optoelectronic materials due to their high specific surface area, regular pore structure, and atomic-level structural designability. Chiral COFs (CCOFs), in particular, can be endowed with strong chiral optical activity by introducing chiral building blocks or undergoing post-synthetic chiral modification, making them ideal candidate materials for constructing CPL detectors. However, current applications of CCOFs in CPL detection are mainly limited to solid-state photoconductive devices. These devices are limited by low exciton dissociation efficiency and short carrier transport distance, and cannot overcome the "intrinsic chiral absorption limitation," making it difficult to obtain highly sensitive detection signals.

[0004] To overcome the aforementioned limitations, amplifying the weak spin optical signal is crucial. Spin-dependent electrochemical reactions (such as the oxygen evolution reaction, OER) have been shown to possess unique spin amplification effects: due to the spin mismatch between the OER product (triplet oxygen) and the reactant, the reaction kinetics are highly sensitive to the spin polarization of the intermediate, theoretically serving as a highly efficient signal gain module. The abundant functional groups in COF materials provide an excellent platform for their metallization modification. Unfortunately, a material system that organically integrates "photogenerated spin polarization of chiral COFs" with "spin-selective OER catalysis at metal sites" is currently lacking. If heavy metal atoms can be introduced into the COF framework to enhance spin-orbit coupling (SOC), and its porous structure can be used to promote electrolyte transport, it is hoped that a novel electrochemical CPL detector integrating "spin generation-spin amplification-current readout" can be constructed. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention aims to provide a method for preparing a metallized chiral COF and its application in electrochemical circularly polarized light detection. The method for preparing the metallized chiral COF includes: synthesizing a chiral COF via a solvothermal reaction using 1,3,5-tricarboxymethylphloroglucinol, trimethylaniline, a chiral inducing agent, and 2,2'-bipyridine-5,5'-diamine as raw materials; subsequently, a coordination reaction with a metal salt in an alcohol solvent is carried out to obtain the metallized chiral COF material. This invention utilizes the prepared metallized chiral COF material as a photoanode material, coupling the spin polarization induced by circularly polarized light (CPL) with the spin-selective oxygen evolution reaction (OER), and amplifying the microscopic spin signal using the nonlinear characteristics of the OER reaction kinetics. This material exhibits excellent photocurrent anisotropy factor (g). Iph This improves stability and solves the problem of low sensitivity in existing solid-state CPL detectors.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing a metallized chiral COF, comprising the following steps in sequence: S1. Synthesis of chiral COF: 1,3,5-tricarboxymethyl phloroglucinol, trimethylaniline, and a chiral inducer were dissolved together in a mixture of 1,4-dioxane and mesitylene in a volume ratio of 1:1. The mixture was pre-stirred for 10-20 min. Then, 2,2'-bipyridine-5,5'-diamine and a 6.0 mol / L acetic acid solution were added to the mixture. The reaction was carried out under closed conditions as a solvothermal reaction. After the reaction was completed, the mixture was separated and washed, and then dried at 80-100 °C for 20-30 h to obtain chiral COF nanosheets. This invention employs a mixed solvent system of 1,4-dioxane and mesitylene, which provides a suitable solubility and polar environment, which is most conducive to the orderly assembly of the reactants and the formation of a highly crystalline COF framework. The concentration and amount of acetic acid solution used in this invention can effectively promote the Schiff base reaction while ensuring the reversibility of the reaction to repair defects and improve crystallinity. S2. Synthesis of metallized chiral COF: The chiral COF nanosheets obtained in step S1 were dispersed in an alcohol solvent, and then a metal salt was added to it. The reaction was carried out under an inert atmosphere and heated under reflux. After the reaction was completed, the reaction system was cooled to room temperature, the precipitate was collected by centrifugation, the precipitate was washed with methanol, and dried under vacuum at 60-80 °C for 24-48 h to obtain the metallized chiral COF material.

[0007] As a limitation of the preparation method of the present invention, in step S1, the chiral inducer is (R)-1-phenylethylamine or (S)-1-phenylethylamine.

[0008] As another limitation of the preparation method of the present invention, in step S1, the molar ratio of 1,3,5-tricarboxymethyl phloroglucinol, trimethylaniline, chiral inducer and 2,2'-bipyridine-5,5'-diamine is 1:1:1:1.5; and the molar volume ratio of 2,2'-bipyridine-5,5'-diamine to acetic acid solution is 0.15:300 mmol / μL.

[0009] As a third limitation of the preparation method of the present invention, in step S1, the temperature of the solvothermal reaction is 110-130℃ and the time is 40-50 h. Under this temperature and time, the COF material has the best thermodynamic stability and can form a nanosheet structure with regular morphology and good dispersibility.

[0010] As a fourth limitation of the preparation method of the present invention, in step S2, the metal salt is cobalt chloride or cobalt acetate.

[0011] As a fifth limitation of the preparation method of the present invention, in step S2, the mass ratio of the chiral COF nanosheet to the metal salt is 26:(10-20). This mass ratio can ensure that the metal ions fully fill the coordination vacancies, achieve high loading of metallization, and thus enhance the spin-orbit coupling effect.

[0012] As a sixth limitation of the preparation method of the present invention, in step S2, the alcohol solvent is methanol or ethanol. Alcohols, as polar solvents, are conducive to the dissolution and diffusion of metal salts into the COF channels, and at the same time, they will not destroy the framework structure of COF at the reflux temperature.

[0013] As a seventh limitation of the preparation method of the present invention, in step S2, the temperature of the heating reflux reaction is 70-90℃ and the time is 10-14 h. This condition not only ensures the thermodynamic requirements of the coordination reaction, but also avoids the possibility of skeleton collapse or metal agglomeration that may be caused by prolonged high temperature.

[0014] This invention also provides an application of metallized chiral COF in a circularly polarized light detector. The metallized chiral COF material prepared by the above method is coated on the surface of a conductive substrate as a working electrode to construct an electrochemical CPL detection system. The system uses 1 M KOH solution as the electrolyte, Hg / HgO as the reference electrode, and a carbon rod as the counter electrode.

[0015] As a limitation of the application of the present invention, the circularly polarized light detector detects the difference in photocurrent response between left-handed and right-handed circularly polarized light through photoelectrochemical testing.

[0016] The above-described technical solution of this invention, as a whole, involves interconnected and mutually influential steps, which collectively determine the morphological characteristics and properties of the product. The reason why the metallized chiral COF material prepared by this invention can achieve photocurrent anisotropy factor (g) is...iph The significant improvement lies in the construction of a cascaded signal conversion mechanism of "spin generation-spin amplification-current readout," which breaks through the linear conversion limitation of traditional solid-state detectors that rely solely on intrinsic circular dichroism absorption. When circularly polarized light (CPL) irradiates a chiral COF framework, due to the optical transition selection rule, the absorption cross-section of the material for left-handed and right-handed circularly polarized light differs, generating excitons with a net spin polarization direction. In the chiral microenvironment constructed by the chiral inducing agent [(R)-1-phenylethylamine or (S)-1-phenylethylamine], these excitons dissociate into spin-polarized charge carriers, whose spin polarization direction (up or down) is directly related to the spin direction of the incident CPL. However, this intrinsic spin polarization signal is extremely weak. In traditional solid-state devices, charge carriers are only transported through external circuits to form photocurrent, and its asymmetry is directly limited by the circular dichroism (CD) absorption coefficient of the material, leading to g iph It is usually less than 0.1.

[0017] This invention injects the aforementioned spin-polarized charge carriers into the active sites of metallic cobalt (Co) anchored on the COF framework, driving the OER. The OER exhibits unique spin-dependent nonlinear kinetics: its final product is triplet O2, and its formation requires two electrons to have a spin-parallel state (↑↑). Therefore, the OER reaction pathway is highly sensitive to the electron spin state at the catalytic site, exhibiting a strong "spin filtering" effect. Cobalt (Co, Z=27), as a transition metal, has an atomic number much higher than the lighter elements constituting the COF framework. When Co... 2+ When coordinating with bipyridine (bpy) to form a Co-N coordination bond, the d orbitals of the metal center overlap with the electron clouds of the π-conjugated system of COF. This electronic structure coupling transmits the strong SOC effect introduced by the high-Z atoms to the entire photoelectric active region. The strong SOC breaks the spin-forbidden constraint between the singlet and triplet states. In the electrochemical OER process, the enhanced SOC stabilizes the specific spin configuration of the catalytic intermediate, suppresses spin decoherence caused by spin-lattice interactions, and ensures that the initial spin polarization information induced by CPL can be efficiently transmitted to the OER reaction pathway.

[0018] When LCP and RCP are irradiated, the spin-polarized carriers generated by the metallized chiral COF materials form a catalytic interface microenvironment with opposite net spin directions at the Co sites. Assuming LCP irradiation generates more "spin-up" carriers, the formation energy barrier of OER intermediates (such as *OOH, *O) on the Co active center will be significantly reduced due to spin-matching, resulting in an exponential increase in reaction kinetics and thus promoting the photocurrent of LCP. Conversely, the "spin-down" carriers generated by RCP irradiation mismatch with the spin state required for OER, leading to an increased reaction energy barrier and impeded kinetics, thus inhibiting the photocurrent of RCP and distinguishing between LCP and RCP. This spin-dependent difference in catalytic kinetics constitutes an internal gain module: a small difference in spin polarization is amplified into a significant difference in macroscopic photocurrent through the nonlinear response of OER kinetics. This mechanism enables g iph Reaching over 0.35, this is more than three times higher than that of solid-state devices, achieving highly efficient electrochemical amplification of microscopic spin signals.

[0019] The metallized chiral COF material prepared in this invention utilizes the heavy atom effect of the metal center to enhance spin-orbit coupling (SOC) and amplifies the asymmetry of photocurrent through spin-selective oxygen evolution reaction (OER). Figure 13 (As shown). The chiral COF framework is mainly composed of light elements (C, H, O, N, atomic number Z≤8) through covalent bonds. According to perturbation theory, the SOC strength is proportional to the fourth power of the nuclear charge (ζ∝Z). 4 Therefore, the intrinsic SOC constant of a pure organic framework is extremely weak (typically <1 meV). This weak SOC results in photogenerated excitons being in a weakly coupled state between singlet and triplet states. Spin-polarized carriers are prone to spin relaxation and spin flipping, causing the initial spin polarization induced by CPL to decay almost entirely before reaching the electrode, making it difficult to detect effectively. Cobalt (Co, Z=27), as a transition metal, has an atomic number much higher than the lighter elements constituting the COF framework. When Co... 2+ When coordinating with bipyridine (bpy) to form a Co-N coordination bond, the d orbitals of the metal center overlap with the electron clouds of the π-conjugated system of COF. This electronic structure coupling transmits the strong SOC effect introduced by the high-Z atom to the entire photoelectric active region. Locally at the Co site, due to the significant increase in the nuclear charge Z, the relativistic effect is enhanced, and the SOC term H in the Hamiltonian increases. SOCThe coupling constant ξ(r) of ξ(r)L·S (where L is the orbital angular momentum operator and S is the spin angular momentum operator) increases significantly. Strong SOC breaks the spin forbidden constraint between singlet and triplet states. In the electrochemical OER process, enhanced SOC stabilizes the specific spin configuration of the catalytic intermediate, suppresses spin decoherence caused by spin-lattice interactions, and ensures that the initial spin polarization information induced by CPL can be efficiently transferred to the OER reaction pathway.

[0020] The enhanced SOC not only improves the generation efficiency and lifetime of spin-polarized carriers, but more importantly, it transforms the Co active center into a spin-active catalytic site. In the rate-determining step of the OER, the Co center, through the strong SOC effect of its d orbitals, preferentially captures carriers matching its own spin state, forming a spin-polarized reaction intermediate. This spin-selective charge injection, synergistically with the nonlinear amplification effect of the subsequent OER kinetics, constitutes the physicochemical basis for the high-sensitivity CPL detection of this invention.

[0021] The above technical solution has the following advantages or beneficial effects: 1. This invention utilizes a solvothermal method to induce the synthesis of highly crystalline chiral COF nanosheets with abundant bipyridine sites using chiral amines; through a post-modification strategy, transition metal ions (Co) are precisely anchored onto the COF framework under reflux conditions in an alcohol solvent to obtain metallized chiral COF materials; 2. This invention is the first to apply cobalt-metallized chiral covalent organic frameworks as photoelectrode materials to electrochemical circularly polarized light detection. Unlike traditional solid-state CPL detectors (which mainly rely on weak photoconductive effects), this invention utilizes cobalt-metallized chiral covalent organic frameworks to construct a detection mechanism of "chiral light absorption - spin polarization generation - electrochemical spin amplification", providing a new technical path to solve the problem of weak photoresponse signals of chiral organic materials. 3. This invention utilizes anchored metal sites as spin-selective OER catalytic centers, leveraging the nonlinear kinetics of the OER reaction to amplify weak microscopic spin polarization signals into significant macroscopic photocurrent signals. Compared to solid-state devices made of similar materials, the cobalt-metallized chiral covalent organic framework electrochemical detector fabricated in this invention achieves a photocurrent anisotropy factor (g) Iph The significant improvement in performance has broken through the performance bottleneck of traditional solid-state devices; 4. The metallized chiral COF material prepared by this invention has excellent chemical stability and structural designability. The high specific surface area and regular pore structure of the COF material are conducive to electrolyte transport and exposure of active sites, while the robust covalent backbone ensures its stability in long-term electrochemical cycling tests. It solves the problem of easy deactivation of traditional chiral organic small molecules in electrochemical environment and has good prospects for device application.

[0022] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0023] Figure 1 This is a diagram of an electrochemical CPL detector device in an application example of the present invention; Figure 2 This is a device diagram of the solid-state devices in Comparative Examples 3 and 4 of the present invention; Figure 3 The following are powder X-ray diffraction (PXRD) patterns of the COF materials prepared in Examples 1-2 and Comparative Example 1 of this invention. Figure 4 XPS high-resolution spectrum of the N 1s orbital of the metallized chiral COF material (Co-R-CCOF) prepared in Example 1 of this invention; Figure 5 The N2 adsorption-desorption isotherm and pore size distribution (BET) diagram of the metallized chiral COF material (Co-R-CCOF) prepared in Example 1 of this invention are shown. Figure 6 An atomic force microscope (AFM) image of the metallized chiral COF material (Co-R-CCOF) prepared in Example 1 of this invention; Figure 7 In an application example of this invention, the photocurrent response diagram and photocurrent anisotropy factor (g) of the electrochemical CPL detector assembled based on Example 1 (Co-R-CCOF) under LCP and RCP irradiation are shown. Iph Calculation results graph; Figure 8 In an application example of this invention, the photocurrent response diagram and photocurrent anisotropy factor (g) of the electrochemical CPL detector assembled based on Example 2 (Co-S-CCOF) under LCP and RCP irradiation are shown. Iph Calculation results graph; Figure 9 The photocurrent response diagram of the electrochemical CPL detector prepared based on Comparative Example 1 (Co-rac-COF) in Comparative Example 2 of this invention is shown. Figure 10 This is the photocurrent response diagram of the solid-state CPL detector device prepared based on Example 1 (Co-R-CCOF) in Comparative Example 3 of the present invention; Figure 11 This is the photocurrent response diagram of the solid-state CPL detector device prepared based on Example 2 (Co-S-CCOF) in Comparative Example 4 of the present invention; Figure 12 The application examples of this invention (electrochemical detector) and comparative examples 3-4 (solid-state devices) demonstrate the difference in photocurrent anisotropy factor (g).Iph Numerical comparison chart; Figure 13 This is a schematic diagram of the spin-amplified electrochemical CPL detector of the present invention. Detailed Implementation

[0024] The following embodiments are merely some, not all, of the embodiments of the present invention. Therefore, the detailed descriptions of the embodiments provided below are not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0025] In this invention, unless otherwise specified, all equipment and raw materials are commercially available or commonly used in the industry. The CAS number for 1,3,5-tricarboxymethyl phloroglucinol (Tp) is 34374-88-4, and the CAS number for 2,2'-bipyridine-5,5'-diamine (Bpy) is 52382-48-6. Unless otherwise specified, the methods in the following examples are conventional methods in the art.

[0026] Example 1 This embodiment prepares a metallized chiral COF, and the preparation process and steps are as follows: S1. Synthesis of chiral COF: 0.1 mmol of 1,3,5-tricarboxymethyl phloroglucinol, 0.1 mmol of trimethylaniline, and 0.1 mmol of (R)-1-phenylethylamine were dissolved in 3 mL of a mixture of 1,4-dioxane and mesitylene at a volume ratio of 1:1. The mixture was pre-stirred for 15 min. Then, 0.15 mmol of 2,2'-bipyridine-5,5'-diamine and 300 μL of 6.0 mol / L acetic acid solution were added to the mixture. The mixture was transferred to a pressure-resistant tube, degassed three times by liquid nitrogen, sealed, and placed in an oven at 120 °C for 48 h. After the reaction, the reaction system was cooled to room temperature, and the precipitate was collected by centrifugation. The precipitate was washed with tetrahydrofuran and acetone, and then vacuum dried at 80 °C for 30 h to obtain chiral COF nanosheets (R-CCOF). S2. Synthesis of metallized chiral COF: 26 mg of R-CCOF powder obtained in step S1 was dispersed in 40 mL of anhydrous methanol. After ultrasonic dispersion, 16 mg of anhydrous cobalt chloride (CoCl2) was added. Under nitrogen protection, the reaction system was heated to 80 °C and stirred under reflux for 12 h. After the reaction was completed, the reaction system was cooled to room temperature, and the precipitate was collected by centrifugation. The precipitate was repeatedly washed with methanol to remove uncoordinated cobalt salts, and then vacuum dried at 60 °C for 24 h under vacuum to obtain the metallized chiral COF material (Co-R-CCOF).

[0027] Example 2 This embodiment prepares a metallized chiral COF, and the preparation process and steps are as follows: S1. Synthesis of chiral COF: 0.1 mmol of 1,3,5-tricarboxymethyl phloroglucinol, 0.1 mmol of trimethylaniline, and 0.1 mmol of (S)-1-phenylethylamine were dissolved in 3 mL of a mixture of 1,4-dioxane and mesitylene at a volume ratio of 1:1. The mixture was pre-stirred for 10 min. Then, 0.15 mmol of 2,2'-bipyridine-5,5'-diamine and 300 μL of 6.0 mol / L acetic acid solution were added to the mixture. The mixture was transferred to a pressure-resistant tube, degassed three times by liquid nitrogen, sealed, and placed in an oven at 110 °C for 50 h. After the reaction, the reaction system was cooled to room temperature, and the precipitate was collected by centrifugation. The precipitate was washed with tetrahydrofuran and acetone, and then dried under vacuum at 90 °C for 25 h to obtain chiral COF nanosheets (S-CCOF). S2. Synthesis of metallized chiral COF: 26 mg of S-CCOF powder obtained in step S1 was dispersed in 40 mL of anhydrous methanol. After ultrasonic dispersion, 10 mg of anhydrous cobalt chloride (CoCl2) was added. Under nitrogen protection, the reaction system was heated to 70 °C and stirred under reflux for 14 h. After the reaction was completed, the reaction system was cooled to room temperature, and the precipitate was collected by centrifugation. The precipitate was repeatedly washed with methanol to remove uncoordinated cobalt salts and then vacuum dried at 70 °C for 48 h under vacuum to obtain the metallized chiral COF material (Co-S-CCOF).

[0028] Example 3 This embodiment prepares a metallized chiral COF, and the preparation process and steps are as follows: S1. Synthesis of chiral COF: 0.1 mmol of 1,3,5-tricarboxymethyl phloroglucinol, 0.1 mmol of trimethylaniline, and 0.1 mmol of (R)-1-phenylethylamine were dissolved in 3 mL of a mixture of 1,4-dioxane and mesitylene at a volume ratio of 1:1. The mixture was pre-stirred for 20 min. Then, 0.15 mmol of 2,2'-bipyridine-5,5'-diamine and 300 μL of 6.0 mol / L acetic acid solution were added to the mixture. The mixture was transferred to a pressure-resistant tube, degassed three times by liquid nitrogen, sealed, and placed in an oven at 130 °C for 40 h. After the reaction, the reaction system was cooled to room temperature, and the precipitate was collected by centrifugation. The precipitate was washed with tetrahydrofuran and acetone, and then dried under vacuum at 100 °C for 20 h to obtain chiral COF nanosheets (R-CCOF). S2. Synthesis of metallized chiral COF: 26 mg of R-CCOF powder obtained in step S1 was dispersed in 40 mL of anhydrous methanol. After ultrasonic dispersion, 20 mg of anhydrous cobalt chloride (CoCl2) was added. Under nitrogen protection, the reaction system was heated to 90 °C and stirred under reflux for 10 h. After the reaction was completed, the reaction system was cooled to room temperature, and the precipitate was collected by centrifugation. The precipitate was repeatedly washed with methanol to remove uncoordinated cobalt salts, and then vacuum dried at 80 °C for 36 h under vacuum to obtain the metallized chiral COF material (Co-R-CCOF).

[0029] Application examples 1. Electrode preparation: Co-R-CCOF prepared in Example 1 and Co-S-CCOF prepared in Example 2 were dispersed in a mixture of ethanol and Nafion to form a slurry, which was then drop-coated onto the surface of carbon paper (loading amount approximately 1 mg / cm). 2 ) is used as the working electrode.

[0030] 2. Test Method: The photoelectrochemical CPL detection performance was evaluated using a 300 W xenon lamp as the light source. To generate circularly polarized light, unpolarized light from the light source passed sequentially through a mirror, a condenser lens, and an integrated polarization module consisting of a linear polarizer and a quarter-wave plate (QWP). By manually switching between two pre-calibrated integrated polarization modules, left-handed (LCP, σ) light was obtained. + ) and right-handed (RCP, σ - Circularly polarized light. On a CHI 760E electrochemical workstation, with Hg / HgO as the reference electrode and a carbon rod as the counter electrode, the transient photocurrent response under CPL irradiation at a bias voltage of 0.8 V was recorded in 1 M KOH electrolyte.

[0031] Comparative Example To investigate the influence of different raw materials on the performance of the product during the preparation process of this invention, the following comparative experiments were conducted. Different COF materials were prepared and applied to circularly polarized light detectors, as detailed below: Comparative Example 1 In this comparative example, a COF material was prepared. The preparation process was similar to that in Example 1, except that in step S1, racemic 1-phenylethylamine (rac-1-phenylethylamine) was used instead of (R)-1-phenylethylamine to prepare racemic COF nanosheets (rac-COF). Step S2 was the same as in Example 1 to obtain racemic cobalt metallized COF material (Co-rac-COF).

[0032] Comparative Example 2 This comparative example uses the Co-rac-COF prepared in Comparative Example 1 as the working electrode material, which is applied in a circularly polarized light detector. The electrode preparation method and test conditions are exactly the same as those in the application example.

[0033] Comparative Example 3 This comparative example uses the Co-R-CCOF powder prepared in Example 1 to prepare a solid-state photodetector and applies it to a circularly polarized photodetector.

[0034] 1. Solid-state photodetector: 5 mg Co-R-CCOF (10 wt.%), 10 mg conductive carbon black (20 wt.%), and 35 mg polyvinylidene fluoride (PVDF) (70 wt.%) were mixed and ground uniformly in a mortar. The mixture was then transferred to a molding die (13 mm inner diameter) and a photoactive layer was prepared under 20 MPa high pressure. The resulting active layer was dried under vacuum at 80 °C for 12 h. The prepared active layer was then attached to a silicon wafer covered with 300 nm SiO2, and a Cu mask (200 μm × 40 μm) was attached to the active layer for electrode array deposition. Subsequently, an electrode array (Ti / Au: 6 nm / 70 nm) with dimensions of 200 μm × 40 μm was deposited by vacuum evaporation. After removing the mask, the photodetector at both ends in the horizontal direction was obtained. 2. Test Method: The same light source and circular polarizer were used as in the electrochemical detector test. The optical power density of the CPL was measured using a densitometer, and LCP and RCP were obtained by switching between two calibrated integrated polarization modules. The photocurrent was monitored using a Keithley 2636b semiconductor analyzer. The electrical bias was maintained at 1 V throughout all measurements.

[0035] Comparative Example 4 In this comparative example, the Co-S-CCOF powder prepared in Example 2 was used to prepare a solid-state photodetector and applied to a circularly polarized photodetector. The device preparation process and testing conditions were exactly the same as those in Comparative Example 3.

[0036] <Structural Characterization and Performance Testing> The COF materials prepared in Examples 1-3 and Comparative Example 1 of this invention were subjected to a series of structural characterizations, and a series of performance tests were conducted corresponding to the use cases and Comparative Examples 2-4, as detailed below: Figure 1 and Figure 2 This is a schematic diagram of the electrochemical CPL detector and solid-state device in this invention. From... Figure 1 It can be seen that the electrochemical CPL detector designed in this invention constructs an interface between the photoanode and the electrolyte, which can initiate the oxygen evolution reaction (OER) under illumination, unlike... Figure 2 Traditional solid-state photoconductive devices.

[0037] The metallized chiral COF material (Co-R-CCOF) prepared in Example 1 was characterized for its material structure, and the results are as follows: Figures 3 to 6 As shown.

[0038] from Figure 3 The PXRD pattern shows that Co-R-CCOF is at 3.5... ° The COF framework exhibits sharp and strong diffraction peaks, indicating that after the introduction of metal ions for post-modification coordination, the COF framework still maintains a good long-range ordered structure and high crystallinity, and no framework collapse has occurred.

[0039] from Figure 4 The XPS N 1s high-resolution energy spectrum shows that, compared with the unmetallized precursor, the binding energy of pyridine nitrogen has shifted significantly, and a characteristic peak belonging to the Co-N bond appears at a higher binding energy. This strongly proves that the cobalt ion has been successfully coordinated to the bipyridine site of the COF framework, providing a catalytic active center.

[0040] from Figure 5 The N2 adsorption-desorption isotherms show that the material exhibits type IV isotherm characteristics and has a rich mesoporous structure. This porosity is beneficial for electrolyte wetting and ion transport.

[0041] from Figure 6 As can be seen from the AFM diagram, the exfoliated Co-R-CCOF exhibits a flat surface and uniform thickness of nanosheet morphology, with a thickness of approximately 9-12 nm. This ultrathin two-dimensional structure is conducive to the rapid migration of photogenerated carriers to the surface to participate in the reaction.

[0042] The photocurrent response of the electrochemical CPL detector (based on Co-R-CCOF and Co-S-CCOF) assembled in the application examples of this invention was tested, and the results are as follows: Figure 7 and Figure 8 As shown.

[0043] from Figure 7 It can be seen that the photocurrent of the Co-R-CCOF-based detector under left-handed circularly polarized light (LCP) illumination is significantly higher than that under right-handed circularly polarized light (RCP). The calculated photocurrent anisotropy factor (g) Iph (Up to 0.35).

[0044] from Figure 8 It can be seen that the detector based on Co-S-CCOF exhibits a perfect mirror-symmetric response, that is, the RCP photocurrent is significantly higher than that of LCP (g Iph =0.38). This indicates that the material prepared in this invention has excellent circularly polarized light recognition capability, and the macroscopic chiral direction of the material directly determines the selective direction of CPL detection.

[0045] The photocurrent response of the electrochemical CPL detector based on Co-rac-COF (racemic) prepared in Comparative Example 2 of this invention was tested, and the results are as follows: Figure 9 As shown.

[0046] from Figure 9 It can be seen that the photocurrent response curves of the racemic material under LCP and RCP irradiation almost completely overlap, and its g Iph The value is close to 0 (only 0.018). This further confirms that the chiral structure of the material is a prerequisite for generating spin-polarized charge carriers and thus realizing CPL detection. Without a chiral structure, it is impossible to distinguish circularly polarized light with different spin directions.

[0047] The solid-state CPL detectors fabricated based on Co-R-CCOF and Co-S-CCOF in Comparative Examples 3 and 4 of this invention were observed, and the results are as follows: Figure 10 and Figure 11 As shown.

[0048] from Figure 10 and Figure 11 It can be seen that, in solid-state device structures without an electrolyte system, although Co-R-CCOF and Co-S-CCOF still exhibit certain chiral photocurrent responses (LCP>RCP for Co-R-CCOF, RCP>LCP for Co-S-CCOF), their photocurrent anisotropy factors (g) are significantly different. IphThe values ​​are relatively low, only around 0.11 and 0.13 respectively. This indicates that in the traditional solid-state photoconductive mode, the detection sensitivity of the device is mainly limited by the intrinsic circular polarization light absorption difference of the material, lacking an effective signal gain mechanism, making it difficult to achieve high-sensitivity detection.

[0049] The photocurrent anisotropy factor of the application example (electrochemical detector) was compared with that of Comparative Example 3 (solid-state device), and the results are as follows: Figure 12 As shown.

[0050] from Figure 12 It can be seen that g obtained using the electrochemical detection method of this invention Iph =0.35 is the g of the same material in solid-state devices. Iph =More than 3 times that of 0.11. This significant performance improvement is attributed to the unique "electrochemical spin amplification" mechanism of this invention: in the electrochemical system, photo-excited spin-polarized charge carriers are injected into Co sites to participate in OER. Since the formation of triplet oxygen in the OER product has a high spin selectivity, small differences in spin polarization lead to huge differences in the OER reaction kinetic rate, thereby amplifying the microscopic spin signal into a macroscopic current signal. Figure 12 This study visually demonstrates the crucial role of the electrochemical environment combined with spin-active sites in improving CPL detection performance, proving the significant advantages of this strategy in overcoming the sensitivity bottleneck of traditional solid-state devices.

[0051] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a metallized chiral COF, characterized in that, Follow these steps in sequence: S1. Synthesis of chiral COF: 1,3,5-tricarboxymethyl phloroglucinol, trimethylaniline, and a chiral inducer were dissolved together in a mixture of 1,4-dioxane and mesitylene in a volume ratio of 1:

1. The mixture was pre-stirred for 10-20 min. Then, 2,2'-bipyridine-5,5'-diamine and a 6.0 mol / L acetic acid solution were added to the mixture. The reaction was carried out under closed conditions as a solvothermal reaction. After the reaction was completed, the reaction system was cooled to room temperature, and the precipitate was collected by centrifugation. The precipitate was washed with tetrahydrofuran and acetone and dried under vacuum at 80-100 °C for 20-30 h to obtain chiral COF nanosheets. S2. Synthesis of metallized chiral COF: The chiral COF nanosheets obtained in step S1 were dispersed in an alcohol solvent, and then a metal salt was added to it. The reaction was carried out under an inert atmosphere and heated under reflux. After the reaction was completed, the reaction system was cooled to room temperature, the precipitate was collected by centrifugation, the precipitate was washed with methanol, and dried under vacuum at 60-80 °C for 24-48 h to obtain the metallized chiral COF material.

2. The method for preparing a metallized chiral COF according to claim 1, characterized in that, In step S1, the chiral inducer is (R)-1-phenylethylamine or (S)-1-phenylethylamine.

3. The method for preparing a metallized chiral COF according to claim 1, characterized in that, In step S1, the molar ratio of 1,3,5-tricarboxymethyl phloroglucinol, trimethylaniline, chiral inducer and 2,2'-bipyridine-5,5'-diamine is 1:1:1:1.5; the molar volume ratio of 2,2'-bipyridine-5,5'-diamine to acetic acid solution is 0.15:300 mmol / μL.

4. The method for preparing a metallized chiral COF according to claim 1, characterized in that, In step S1, the temperature of the solvothermal reaction is 110-130 °C and the time is 40-50 h.

5. The method for preparing a metallized chiral COF according to claim 1, characterized in that, In step S2, the metal salt is cobalt chloride or cobalt acetate.

6. The method for preparing a metallized chiral COF according to claim 1, characterized in that, In step S2, the mass ratio of the chiral COF nanosheets to the metal salt is 26:(10-20).

7. The method for preparing a metallized chiral COF according to claim 1, characterized in that, In step S2, the alcohol solvent is methanol or ethanol.

8. The method for preparing a metallized chiral COF according to claim 1, characterized in that, In step S2, the temperature of the heating reflux reaction is 70-90 °C, and the time is 10-14 h.

9. The application of a metallized chiral COF according to any one of claims 1-8 in a circularly polarized optical detector, characterized in that, The metallized chiral COF material prepared by the above method is coated on the surface of a conductive substrate as a working electrode to construct an electrochemical CPL detection system; the system uses 1 M KOH solution as electrolyte, Hg / HgO as reference electrode, and carbon rod as counter electrode.

10. The application of a metallized chiral COF in a circularly polarized optical detector according to claim 9, characterized in that, The circularly polarized light detector detects the difference in photocurrent response between left-handed and right-handed circularly polarized light through photoelectrochemical testing.

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