阅读说明：本技术 一种零价银掺杂的银基配位聚合物及其制备方法和应用 (Zero-valent silver-doped silver-based coordination polymer and preparation method and application thereof ) 是由 周实 姜维 刘博� 周天瑜 车广波 于 2021-07-20 设计创作，主要内容包括：一种银基配位聚合物和一种零价银掺杂的银基配位聚合物光催化降解甲基橙及其制备方法与应用,属于配位聚合物技术领域,针对光催化降解甲基橙催化剂活性低、光生载流子易于复合等缺陷,本发明提供了一种银基配位聚合物,其分子式为[Ag-(3)(psa)(4,4’-bpy)-(6)]-(n)·nOH·2nCH-(3)OH·2nH-(2)O,式中psa代表苯基丁二酸盐,4,4’-bpy代表4,4’-联吡啶；该化合物属于三斜晶系中的P1空间群,且结构中存在着独立的一维链与二维层。经汞灯预照射不同时间,因为配位聚合物中部分一价银可以还原为零价银,获得零价银掺杂的银基配位聚合物。上述催化剂在可见光下可以催化降解甲基橙,尤其是汞灯预照射1小时的零价银掺杂的银基配位聚合物具有最佳催化活性。(A silver-based coordination polymer, a zero-valent silver-doped silver-based coordination polymer photocatalytic degradation methyl orange, a preparation method and application thereof, belongs to the technical field of coordination polymers, and aims at low activity of a photocatalytic degradation methyl orange catalyst,The invention provides a silver-based coordination polymer with a molecular formula of [ Ag [ ] 3 (psa)(4,4’‑bpy) 6 ] n ·nOH·2nCH 3 OH·2nH 2 O, wherein psa represents phenyl succinate and 4,4 '-bpy represents 4, 4' -bipyridine; the compound belongs to a P1 space group in a triclinic system, and independent one-dimensional chains and two-dimensional layers exist in the structure. Pre-irradiating by mercury lamp for different time, because part of univalent silver in the coordination polymer can be reduced to zero-valent silver, and obtaining the zero-valent silver-doped silver-based coordination polymer. The catalyst can catalyze and degrade methyl orange under visible light, and particularly, the zero-valent silver-doped silver-based coordination polymer with the mercury lamp pre-irradiation for 1 hour has the optimal catalytic activity.)

1. The zero-valent silver-doped silver-based coordination polymer is characterized in that the molecular formula of a coordination polymer precursor is [ Ag ]₃(psa)(4,4’-bpy)₆]_n·nOH·2nCH₃OH·2nH₂O, part of Ag in part of Ag precursor⁺In-situ photo-reduction to Ag by mercury lamp illumination⁰Formation of zero-valent silver-doped silver-based coordination polymerizationAn agent;

in the molecular formula, psa represents phenyl succinate, 4,4 '-bpy represents 4, 4' -bipyridine; the coordination polymer belongs to a P1 space group in a triclinic system, and an independent one-dimensional chain and a two-dimensional layer exist in the structure; the asymmetric unit of coordination polymer precursor is formed by that there are 3 central Ag⁺3 4, 4' -bpy and 1 spa, 2 methanol molecules and 2 water molecules and 1 hydroxyl ion; wherein Ag1 and Ag2 ions are in four coordination and are simultaneously coordinated with two oxygen atoms from spa and two nitrogen atoms from 4, 4' -bpy; the Ag3 ion is bidentate and coordinates with two nitrogen atoms from 4, 4' -bpy; ag1 and Ag2 respectively form a one-dimensional chain structure with 4, 4' -bpy, and the two one-dimensional chains are bridged through spa molecules to form an infinite two-dimensional layer along an ac surface;

the bidentate Ag3 forms a one-dimensional chain structure through the connection of 4, 4' -bpy molecules; the independent one-dimensional chain and the two-dimensional layer further form a complex three-dimensional supramolecular structure through the pi-pi accumulation effect between 4, 4' -bpy benzene rings, and the distance between the centroids of the benzene rings is。

2. The method for preparing a silver-based coordination polymer according to claim 1, comprising the following specific steps:

1) adding 0.5mmol of AgNO₃，0.25mmol H₂putting the psa and 0.5mmol of 4, 4' -bpy into a 50mL beaker, adding 10mL of water and 10mL of methanol, stirring on a magnetic stirrer, and dropwise adding ammonia water until the solution is clear; placing the mixture at room temperature in a dark place, sealing the mixture with a preservative film, and slowly evaporating the solution to separate out yellow blocky crystals, namely the silver-based coordination polymer;

2) and adding 100mg of precursor into a photochemical reactor filled with 100mL of deionized water, respectively illuminating for 0.5-2 h under a mercury lamp, and filtering and drying to obtain the silver-based coordination polymers doped with the zero-valent silver with different contents.

3. The zero-valent silver dopant of claim 1The precursor of the silver-based coordination polymer is characterized in that the molecular formula of the precursor of the coordination polymer is [ Ag ]₃(psa)(4,4’-bpy)₆]_n·nOH·2nCH₃OH·2nH₂O，

In the molecular formula, psa represents phenyl succinate, 4,4 '-bpy represents 4, 4' -bipyridine; the coordination polymer belongs to a P1 space group in a triclinic system, and an independent one-dimensional chain and a two-dimensional layer exist in the structure; the asymmetric unit of coordination polymer precursor is formed by that there are 3 central Ag⁺3 4, 4' -bpy and 1 spa, 2 methanol molecules and 2 water molecules and 1 hydroxyl ion; wherein Ag1 and Ag2 ions are in four coordination and are simultaneously coordinated with two oxygen atoms from spa and two nitrogen atoms from 4, 4' -bpy; the Ag3 ion is bidentate and coordinates with two nitrogen atoms from 4, 4' -bpy; ag1 and Ag2 respectively form a one-dimensional chain structure with 4, 4' -bpy, and the two one-dimensional chains are bridged through spa molecules to form an infinite two-dimensional layer along an ac surface;

the bidentate Ag3 forms a one-dimensional chain structure through the connection of 4, 4' -bpy molecules; the independent one-dimensional chain and the two-dimensional layer further form a complex three-dimensional supramolecular structure through the pi-pi accumulation effect between 4, 4' -bpy benzene rings, and the distance between the centroids of the benzene rings is

4. The method for preparing the precursor of the zero-valent silver-doped silver-based coordination polymer according to claim 3, comprising the following steps: adding 0.5mmol of AgNO₃，0.25mmol H₂putting the psa and 0.5mmol of 4, 4' -bpy into a 50mL beaker, adding 10mL of water and 10mL of methanol, stirring on a magnetic stirrer, and dropwise adding ammonia water until the solution is clear; placing the mixture at room temperature in a dark place, sealing the mixture with a preservative film, and slowly evaporating the solution to separate out yellow blocky crystals, namely the silver-based coordination polymer precursor.

5. Use of the silver-based coordination polymer according to claim 1 for visible light catalyzed degradation of methyl orange.

6. Use of the zero-valent silver-doped silver-based coordination polymer of claim 3 for visible light-catalyzed degradation of methyl orange.

Technical Field

The invention belongs to the technical field of coordination polymer materials.

Background

Water pollution is one of the serious problems generally faced by all people today, wherein the pollution of organic dyes in the environment to water resources is serious. Organic dyes are not only toxic but also carcinogenic, their chemical stability and nature that is difficult to degrade in nature pose a serious threat to human health and the sustainability of the ecosystem, and there is an urgent need to develop a method for removing organic dyes from water bodies. Common methods for removing organic dyes include an adsorption method, a membrane separation method, an ion exchange method and a photocatalysis method, and among the methods, the photocatalysis method has low cost and high efficiency, so the method becomes an ideal method for treating organic dye pollution in water.

In recent years, Coordination Polymers (CPs) have been widely used as a highly efficient photocatalyst for CO due to their diverse coordination modes and unique steric structure₂Reduction, hydrogen production, Cr (VI) reduction and degradation of organic pollutants. However, CPs as photocatalysts have a large band gap and generally only absorb visible light, which greatly reduces the utilization rate of solar energy. Due to Ag⁰Has plasma effect, and can show higher photocatalytic activity and stronger light stability when being combined with CPs. In addition, Ag-CPs are rich in Ag⁺Sites, by in situ photoreduction of Ag⁰Doping CPs to improve the charge carrier separation effect of the catalystThe rate, the photocatalytic degradation dye performance is enhanced.

Disclosure of Invention

In order to overcome the defects of high cost, low efficiency and the like of organic dye pollution treatment in water at present, the invention provides a zero-valent silver-doped silver-based coordination polymer, and the molecular formula of a precursor of the coordination polymer is [ Ag ]₃(psa)(4,4’-bpy)₆]_n·nOH·2nCH₃OH·2nH₂O, part of Ag in the precursor⁺In-situ photo-reduction to Ag by mercury lamp illumination⁰And forming the zero-valent silver-doped silver-based coordination polymer.

In the formula, psa represents phenyl succinate, 4,4 '-bpy represents 4, 4' -bipyridine; the coordination polymer belongs to a P1 space group in a triclinic system, and independent one-dimensional chains and two-dimensional layers exist in the structure.

The asymmetric unit in the Ag-CP precursor is composed of 3 central Ag⁺3 4, 4' -bpy and 1 spa, 2 methanol molecules and 2 water molecules and 1 hydroxyl ion; wherein Ag1 and Ag2 ions are in four coordination and are simultaneously coordinated with two oxygen atoms from spa and two nitrogen atoms from 4, 4' -bpy; the Ag3 ion is bidentate and coordinates with two nitrogen atoms from 4, 4' -bpy; ag1 and Ag2 and 4, 4' -bpy form a one-dimensional chain structure respectively, and the two one-dimensional chains are bridged through spa molecules to form an infinite two-dimensional layer along an ac surface.

It is noted that the bidentate Ag3 forms a one-dimensional chain structure by linking 4, 4' -bpy molecules. The independent one-dimensional chain and the two-dimensional layer further form a complex three-dimensional supramolecular structure through the pi-pi accumulation effect between 4, 4' -bpy benzene rings, and the distance between the centroids of the benzene rings is

Part of Ag in the precursor⁺The silver-based coordination polymer doped with zero-valent silver is formed by in-situ photo-reduction to Ag0 through the illumination of a mercury lamp.

The preparation method of the zero-valent silver-doped silver-based coordination polymer precursor comprises the following specific steps:

mixing AgNO₃(0.5mmol,0.085g)，H₂psa (0.25mmol,0.05g) and 4, 4' -bpy (0.5mmol,0.079g) were placed in a 50mL beaker, 10mL of water was added and 10mL of methanol was added, stirred on a magnetic stirrer, and ammonia was added dropwise until the solution cleared. Placing in the dark at room temperature, sealing with plastic wrap, slowly evaporating the solution to precipitate yellow block crystal [ Ag ]₃(psa)(4,4’-bpy)₆]_n·nOH·2nCH₃OH·2nH₂O。

The preparation method of the zero-valent silver-doped silver-based coordination polymer comprises the following specific steps:

and adding 100mg of precursor into a photochemical reactor filled with 100mL of deionized water, respectively illuminating for 0.5-2 h under a mercury lamp, and filtering and drying to obtain the silver-based coordination polymers doped with the zero-valent silver with different contents.

The coordination polymer can be used as a photocatalyst, and can realize visible light catalytic degradation of methyl orange in water.

The invention has the beneficial effects that:

the invention adopts a solution volatilization method to successfully prepare the zero-valent silver-doped silver-based coordination polymer. Loading Ag in prepared precursor crystal by in-situ photo-reduction method⁰And the photocatalytic degradation activity of the CPs is improved. In the zero-valent silver-doped silver-based coordination polymer series photocatalyst, a product (JLNU-91/1) obtained by pre-irradiating for 1h by a mercury lamp has the highest degradation activity under the irradiation of visible light, and the degradation rate of methyl orange can reach 78% after 120min of photocatalysis. In addition, the dosage of the catalyst plays a crucial role in the photocatalytic activity, and 20mg of JLNU-91/1 has the highest degradation activity. Through the capture experiment and ESR test, the O is proved^2-OH and h⁺Is the main active species. Enhancement of photocatalytic activity canDue to Ag in CPs⁺Reduction to Ag⁰Accelerate e^-And h⁺So that the Methyl Orange (MO) can be degraded efficiently. In addition, the JLNU-91/1 photocatalyst still has higher degradation activity even after four photocatalytic cycle experiments under visible light irradiation, which shows that the JLNU-91/1 photocatalyst has high stability.

Drawings

FIG. 1 XRD spectra of JLNU-91 and JLNU-91/x;

FIG. 2(a) JLNU-91, (b) JLNU-91/1, (c) SEM image of photo-catalyzed JLNU-91/1; (d) HRTEM image of JLNU-91/1;

XPS of JLNU-91/1 of FIG. 3, Total spectra (a), C1 s (b), N1s (C), O1s (d), Ag 3d (e);

FIG. 4(a) UV-vis DRS of JLNU-91 and derivatized materials; (b) JLNU-91 and JLNU-91/1 bandgap diagrams;

FIG. 5JLNU-91TG curve;

FIG. 6 is a graph showing photocatalytic degradation curves (a) and first order kinetic curves (b) of JLNU-91 and JLNU-91/x for MO;

FIG. 7 effect of JLNU-91/1 dose on photocatalytic activity;

FIG. 8(a) cycle experiment of JLNU-91/1 photocatalytic degradation of MO; (b) XRD patterns before and after JLNU-91/1 photocatalytic degradation of MO;

FIG. 9 active species trapping experiment of JLNU-91/1 degradation of MO under visible light;

fig. 10 ESR for MO degradation under visible light: JLNU-91/1-C₁₀H₁₀O₄/DMPO (a) and JLNU-91/1-H₂O/DMPO (b) spectrum;

FIGS. 11 photocurrent (a) and electrochemical impedance (b) of JLNU-91 and JLNU-91/1;

FIG. 12 is a schematic diagram of the mechanism of JLNU-91/1 photocatalytic degradation of MO.

Detailed Description

The technical solution of the present invention is further explained and illustrated below in the form of specific examples.

In this example AgNO₃(0.5mmol,0.085g)，H₂psa (0.25mmol,0.05g) and 4, 4' -bpy (0.5mmol,0.079g) were placed in a 50mL beaker, 10mL of water and 10mL of methanol were added, and the mixture was magnetically stirredStirring on the device, and dropwise adding ammonia water until the solution is clear. The solution was left to stand at room temperature in the dark and sealed with a preservative film, and yellow bulk crystals were precipitated by slow evaporation of the solution. For the sake of simplicity, JLNU-91 is used as an abbreviation for this compound.

Elemental analysis (%) C₄₂H₄₄N₆O₉Ag₃: theoretical value: c, 44.16; h, 3.88; n, 11.03; actual values: c, 44.12; h, 3.85; n, 11.06; . IR (KBr, cm)^-1)：3398(w)、3382(w)、3034(m)、1593(m)、1589(m)、1394(s)、1380(s)、1369(s)、998(w)、804(s)、790(s)、705(w)、615(s)、494(s)。

Adding 100mg JLNU-91 into photochemical reactor filled with 100mL deionized water, respectively illuminating under mercury lamp for 0.5h, 1h, 1.5h, and 2h, filtering, and drying to obtain Ag with different contents⁰A doped crystal. These crystals were named JLNU-91/0.5, JLNU-91/1, JLNU-91/1.5, and JLNU-91/2, respectively, depending on the irradiation time of the mercury lamp.

JLNU-91 single crystal diffraction data was obtained using a German Bruker Apex II CCD single crystal diffractometer with the proviso that MoK αThe room temperature was 293K as an incident source, and scanning was performed by ω. The crystal structure of JLNU-91 was resolved by the direct method of the SHELXS-2014 program and refined using the full matrix least squares method F2 of the SHELXL-2014 software. All non-hydrogen atoms are corrected by anisotropic temperature factors and theoretical hydrogenation is used to obtain hydrogen atoms on the ligand. JLNU-91 belongs to the P1 space group in the triclinic system, and the existence of independent one-dimensional chains in the structure and two-dimensional layers tables 1 and 2 are the relevant parameters involved in JLNU-91.

TABLE 1

^aR₁＝Σ||F_o|-|F_c||/Σ|F_o|.^bwR₂＝{Σ[w(F_o ²-F_c ²)²]/Σw(F_o ²)²]}^1/2.

TABLE 2

Symmetric transformations for generating equivalent atoms:^#1:x,y,1+z；^#2-1+x,y,z.

JLNU-91 in this example, a silver-based coordination polymer, has the chemical formula [ Ag₃(psa)(4,4’-bpy)₆]_n·nOH·2nCH₃OH·2nH₂O, wherein psa represents phenyl succinate and 4,4 '-bpy represents 4, 4' -bipyridine; the compound belongs to a P1 space group of a triclinic system, and independent one-dimensional chains and two-dimensional layers exist in the structure. The asymmetric unit comprising 3 Ag⁺6 4, 4' -bpy and 1 spa, 2 methanol molecules and 2 water molecules and 1 hydroxyl ion. Wherein Ag1 and Ag2 ions are four-coordinated and coordinate with two oxygen atoms from spa and two nitrogen atoms from 4, 4' -bpy. The Ag3 ion is bidentate and binds to two nitrogen atoms (N5, N6) from 4, 4' -bpy^#1) And (4) coordination.

Ag1 and Ag2 and 4, 4' -bpy form a one-dimensional chain structure respectively, and the two one-dimensional chains are bridged through spa molecules to form an infinite two-dimensional layer along an ac surface. It is noted that the bidentate Ag3 forms a one-dimensional chain structure by linking 4, 4' -bpy molecules. The independent one-dimensional chain and the two-dimensional layer further form a complex three-dimensional supermolecular structure through the pi-pi accumulation effect between 4, 4' -bpy benzene rings, and the distance between centroids is

X-ray powder diffraction analysis (XRD) of JLNU-91 crystals and derived materials showed: the XRD pattern of JLNU-91 matched well with the corresponding simulated pattern, indicating that the crystal was pure phase, as shown in FIG. 1. JLNU-91 is respectively irradiated under mercury lamp for 0.5-2 h to obtain different Ag⁰The crystal contents are JLNU-91/0.5, JLNU-91/1, JLNU-91/1.5, and JLNU-91/2, respectively. After light exposure, in Ag⁰(111) The corresponding diffraction peak (JCPDS No.87-0719) appeared in the crystal plane (38.1 deg.), probably due to the presence of a small amount of Ag in JLNU-91⁰。

The morphological structures of JLNU-91 and JLNU-91/1 were further characterized by Scanning Electron Microscopy (SEM) and High Resolution Transmission Electron Microscopy (HRTEM). From the SEM picture of JLNU-91 (FIG. 2(a)), it can be seen that JLNU-91 before light irradiation is a block structure with smooth surface and large size. In the process of preparing JLNU-91/1, after irradiation with mercury lamp (FIG. 2(b)), the size became smaller and the surface was rough, which was probably due to Ag⁰Generated on the surface and caused by agitation. The size decreased after photocatalysis but the morphology was maintained, indicating that the morphology of the material did not change significantly during the photocatalytic process (fig. 2 (c)). FIG. 2(d) is a TEM image of JLNU-91/1, from which Ag can be clearly seen⁰The nanoparticles are distributed therein with a lattice fringe spacing of 0.236nm, corresponding to Ag⁰The (111) crystal face of JLNU-91/1 proves Ag⁰Is present.

X-ray photoelectron spectroscopy (XPS) showed that: surface composition and chemical state of JLNU-91/1. FIG. 3(a) is a general spectrum of JLNU-90/1.5, which shows that the crystals synthesized by us contain C, N, O and Ag element. The high resolution XPS spectrum for C1 s can be divided into three major peaks (FIG. 3(b)), with the carbon in the hydroxyl C-OH group appearing at 288.8eV, and the characteristic peaks for the aryl carbon of the phenyl ring at 284.8eV and 285.2 eV. In the spectrum of N1s, 399.6eV corresponds to the C-N bond (FIG. 3 (C). 531.6eV and 531.8eV in FIG. 3(d) correspond to the metal O-Ag of O1s, respectivelyAnd an-OH bond. FIG. 3(e) is a spectrum of Ag 3d, Ag 3d^3/2And Ag 3d^5/2The spin orbit photoelectron peaks are at the binding energies of 374.0eV and 368.2eV, respectively. Furthermore, the two 3d peaks of Ag can be further decomposed into four peaks by XPS peak fitting program. The 367.8eV and 373.7eV peaks are from Ag⁺Peaks at 368.6eV and 374.3eV are Ag⁰. Thus, the high resolution XPS results for Ag 3d confirmed that Ag was in JLNU-91/1⁰Are present.

Solid ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS) indicates: as shown in fig. 4(a), all the absorption edges of the photocatalyst are in the visible light range, indicating that the photocatalyst prepared has visible light response. The band gaps of JLNU-91 and JLNU-91/1 were calculated to be 2.63eV and 2.45eV, respectively, based on the Kubelka-Munk equation (FIG. 4 (b)).

Thermal stability studies showed that JLNU-91 lost weight in two steps, as shown in FIG. 5, the first step occurred between 38-187 deg.C, losing 2 lattice water molecules, 2 methanol molecules and 1 hydroxyl ion (obsd 10.79%, calcd 11.89%), and the second step occurred after 224 deg.C, corresponding to the loss of organic ligands.

Photocatalytic performance analysis

To further understand the photocatalytic performance of JLNU-91 and JLNU-91/x, we performed studies using Methyl Orange (MO) as the target pollutant. Before turning on the lamp, all reaction systems were stirred in the dark for 40min to allow the catalyst to reach adsorption-desorption equilibrium. As can be seen from FIG. 6(a), in the blank experiment without the addition of the catalyst, MO was hardly degraded. After the lamp is started for 120min, the photocatalytic degradation efficiencies of JLNU-91, JLNU-91/0.5, JLNU-91/1, JLNU-91/1.5 and JLNU-9/2 are 49%, 54%, 78%, 75% and 72%, respectively. From the above results, it can be seen that JLNU-91/1 photocatalytic degradation efficiency is best obtained by pre-irradiation with mercury lamp for 1 h. However, the degradation rate of the photocatalytic material obtained by pre-irradiation of the mercury lamp for more than 1 hour was reduced, probably because of Ag generated⁰The catalytic sites are covered. As shown in FIG. 6(b), the trend of the degradation rate constant (k) of different photocatalytic materials was consistent with the photocatalytic degradation curve of FIG. 6(a), and the k values of JLNU-91, JLNU-91/0.5, JLNU-91/1, JLNU-91/1.5, and JLNU-91/2 were calculated to be 0.0056min^-1、0.0063min^-1、0.0124min^-1、0.0108min^-1、0.0105min^-1. The JLNU-91/1 photocatalyst showed an optimal rate constant of approximately 2.2 times that of pure JLNU-91.

In addition, the effect of the amount of photocatalyst used on the photocatalytic activity is discussed. As can be seen from FIG. 7, when the amounts of JLNU-91/1 photocatalyst were 15mg, 20mg, 25mg, and 30mg, respectively, the degradation efficiencies of MO were 54%, 78%, 55%, and 58%, respectively. The photocatalytic performance is improved with the increase of the content. When the content is 20mg, the MO degradation rate is the highest. But the photocatalytic performance is reduced with the increasing content. This may be that excess catalyst prevents light from propagating in solution, affecting the progress of the photocatalytic reaction. Therefore, the effect of the amount of catalyst used cannot be neglected in the photocatalytic process.

The reproducibility of the photocatalyst is an important aspect of testing the stability of the catalyst. The same operation is adopted to carry out the photocatalytic reaction, the catalyst is collected, centrifuged, washed and dried after each reaction is finished, and then the next circulation is carried out. As shown in FIG. 8(a), JLNU-91/1 showed little change in catalytic performance after four cycles of experiments, and still reached more than 75%. As can be seen from XRD patterns before and after the catalyst cycle degradation experiment of fig. 8(b), the catalyst structure was not significantly changed. Therefore, the prepared JLNU-91/1 photocatalyst has good stability.

Analysis of photocatalytic mechanism

To explore the active species in the photocatalytic degradation of MO, we added different sacrificial agents to the system for trapping experiments. As shown in FIG. 9, JLNU-91/1 showed a high MO degradation rate of 78% without any sacrificial agent, and the photocatalytic degradation rate decreased to 15% when IPA and EDTA-2Na were added. Demonstration of OH and h⁺Are the major active species. When L-AA is added into the reaction system, the degradation rate reaches 58 percent, which shows that O is₂ ^-Plays a certain role in the photocatalytic degradation process. Thus, it can be seen that, OH, h⁺And O₂ ^-Is the main active species in the process of photocatalytic degradation of MO.

To further detect the drop of JLNU-91/1OH and O formed during the decomposition₂ ^-The electron paramagnetic resonance spectrometer (ESR) technology is adopted for verification. As is clear from the results of the ESR experiments in FIG. 10, neither OH nor O was observed under dark conditions^2-Four characteristic peaks of DMPO-. OH and DMPO-. O were observed after the lamp was turned on₂ ^-Six characteristic peaks of (A) indicate that after light irradiation JLNU-91/1 can generate OH and O₂ ^-This is consistent with the capture experiment results.

By testing photocurrent response and impedance of a sample, the separation and recombination rules of photo-generated carriers in the photocatalyst are explored. FIG. 11(a) records the transient photocurrent response intensity of JLNU-91 and JLNU-91/1 in visible light. From the figure, it can be observed that the photocurrent response of JLNU-91/1 is much higher than that of JLNU-91. From the impedance diagram of 11(b), it can be seen that the radius of the arc of JLNU-91/1 is smaller than that of JLNU-91. The results of the electrochemical analysis show that JLNU-91/1 has higher efficiency of separating photogenerated electrons and holes and lower efficiency of carrier recombination than JLNU-91.

Based on the results of the active species trapping experiment and ESR testing, the mechanism by which JLNU-91/1 degrades MO under visible light is explained using fig. 12. JLNU-91 is excited to produce a large number of photo-generated electrons and holes when JLNU-91/1 is exposed to visible light. Due to Ag⁰With plasmon resonance effect, e on JLNU-91^-Can be transferred to Ag from conduction band⁰Above, the separation of charges is accelerated. Furthermore, O₂Quilt e^-Reduction to O₂ ^-To degrade h in the valence band of MO, JLNU-91⁺Can be reacted with H₂O reacts to generate OH to effectively degrade MO molecules, h⁺The MO molecules can also be degraded directly.