A lanthanide metal-organic framework and its preparation method and application

Abstract

A lanthanide metal-organic framework, its preparation method, and its application, relates to a metal-organic framework, its preparation method, and its application. The present invention solves the problem that existing Ln-MOFs have poor ligand-metal charge transfer ability, resulting in poor photocatalytic performance. The lanthanide metal-organic framework is composed of {[Ln(BCPI)2(COO)(H2O)2]·H2O} n and closo‑[B 12 H 12 ] 2‑ Method: {[Ln(BCPI)2(COO)(H2O)2]·H2O} n and closo‑[B 12 H 12 ] 2‑ Dissolve in H2O and then heat to react. Application: It is used as a photocatalyst for carbon dioxide reduction. The present invention is used for lanthanide metal organic frameworks and their preparation and application.

Description

Technical Field

[0001] The invention relates to a metal organic framework and a preparation method and application thereof. Background Art

[0002] Lanthanide metal-organic frameworks (Ln-MOFs) are porous crystalline materials assembled from lanthanide metal ions and multidentate organic linkers. Compared to transition-metal-based MOFs, Ln-MOFs possess a greater number of degenerate f orbitals than d orbitals, resulting in stronger coordination bonds, more complex coordination structures, and longer lifetimes. These properties endow Ln-MOFs with great potential in energy and environmental catalysis. Furthermore, the rich orbital levels of lanthanide ions provide a powerful platform for efficient electron transfer and interfacial charge recombination, enabling these materials to excel in capturing and converting small molecules and serve as efficient catalytic centers. Despite these favorable properties, Ln-MOFs' photocatalytic activity, particularly for carbon dioxide conversion, remains unsatisfactory. This limitation stems primarily from their inherently poor ligand-metal charge transfer (LMCT) ability, which hinders the high-performance multiple electron transfer processes required for effective catalysis.

[0003] Many strategies have been adopted to overcome the LMCT limitations of Ln-MOFs, including integrating highly conductive materials, doping with metal ions, and structural or morphological modifications of Ln-MOFs. However, these approaches have failed to significantly enhance the LMCT process within the pores of Ln-MOFs because they are unable to optimize the electron density of the internal microenvironment. Given that efficient CO2 reduction photocatalysts require the promotion of multi-electron transfer processes, improving the LMCT process within Ln-MOFs is crucial. In the existing technology, although lanthanide metal-organic frameworks (Ln-MOFs) have shown potential in photocatalytic CO2 conversion, their performance in practical applications is severely limited. In particular, these materials exhibit significant inertness during the LMCT process, resulting in poor photocatalytic performance. This is mainly due to the insufficient electron density and charge distribution within Ln-MOFs, which makes it difficult to support efficient electron transfer and multi-electron catalytic reactions, thereby affecting their ability to reduce CO2 to useful chemicals. Summary of the Invention

[0004] The present invention aims to solve the problem that the existing Ln-MOFs have poor ligand-metal charge transfer ability, resulting in poor photocatalytic performance, and further provide a method for preparing lanthanide metal-organic frameworks.

[0005] A lanthanide metal organic framework, wherein the lanthanide metal organic framework is composed of {[Ln(BCPI)2(COO)(H2O)2]·H2O} n and closo-[B 12 H 12 ]2- prepared;

[0006] The {[Ln(BCPI)2(COO)(H2O)2]·H2O} n Where n is 1 to 10, Ln is Tb, La, Ce, Sm, Eu or Er; the chemical formula of the lanthanide metal organic framework is [Ln2(BCPI)3(H2O)3(B6H6)3] n , where n = 1 to 10, and Ln is Tb, La, Ce, Sm, Eu or Er.

[0007] A method for preparing a lanthanide metal-organic framework is carried out according to the following steps:

[0008] 1. Reconstitute {[Ln(BCPI)2(COO)(H2O)2]·H2O} n and closo-[B 12 H 12 ] 2- Dissolve in H2O and then stir at room temperature to obtain a reaction system;

[0009] The {[Ln(BCPI)2(COO)(H2O)2]·H2O} n Where n = 1 to 10, Ln is Tb, La, Ce, Sm, Eu or Er;

[0010] 2. Heating the reaction system at 90°C to 95°C for 72 to 120 hours, then cooling to room temperature, and finally centrifuging, washing, and drying to obtain a lanthanide metal-organic framework;

[0011] The chemical formula of the lanthanide metal organic framework is [Ln2(BCPI)3(H2O)3(B6H6)3] n , where n = 1 to 10, and Ln is Tb, La, Ce, Sm, Eu or Er.

[0012] Application of a lanthanide metal-organic framework as a photocatalyst for carbon dioxide reduction.

[0013] The beneficial effects of the present invention are:

[0014] The present invention selects closo-[B 12 H 12 ] 2- As a nanorelay. First, closo-[B 12 H 12 ] 2-As a highly symmetrical nanoscale ion cluster, it can be evenly dispersed in the pores of Ln-MOFs, preventing pore blockage and maintaining the integrity of the material structure. Secondly, the dodecaborane molecule carries two permanent negative charges (2e - ), which is conducive to the efficient electron transfer between the inside and outside, thus facilitating the supply of electrons. Finally, closo-[B 12 H 12 ] 2- The abundant hydrogen bond acceptor (or donor) sites in the closo-[B 12 H 12 ] 2- The clusters flow toward Ln-MOF, generating a synergistic effect inside Ln-MOF and promoting LMCT by changing the distribution of the electron cloud.

[0015] The present invention uses single crystal diffraction to synthesize the lanthanide metal organic framework [Ln2(BCPI)3(H2O)3(B6H6)3] n (B 12 H 12 @Ln-BCPI material) was structurally characterized and confirmed that B 12 H 12 The successful integration of nanorelays into Ln-MOF structures. 12 H 12 ] 2- It was first introduced into the Ln-MOF family and used as a photocatalyst for carbon dioxide reduction reaction.

[0016] The present invention successfully obtained B 12 H 12 The crystal structure of @Ln-BCPI material was studied, and high efficiency and high selectivity of photocatalytic CO2-to-CO conversion were achieved in the presence of triethanolamine (TEOA). The mechanism shows that B 12 H 12 As a nanorelay, the LMCT of Ln-MOF is significantly enhanced, and the Ln center has excellent adsorption and activation capabilities for CO2. This study also illustrates how functional materials, Ln-MOF catalysts, and electron donors work synergistically in the photocatalytic reduction of CO2. This study, based on the modified Ln-MOF, provides insights into the rational design and development of advanced photocatalytic systems for artificial photosynthesis. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Tb-BCPI-1D and B 12 H 12 @Tb-BCPI structural comparison diagram;

[0018] Figure 2 For closo-[B 12 H 12 ] 2- Structural diagram of

[0019] Figure 3 For B 12 H 12 Thermogravimetric analysis of @Tb-BCPI;

[0020] Figure 4 For B 12 H 12 Liquid chromatogram of the solution after Tb-BCPI reduced CO2;

[0021] Figure 5 For closo-[B 12 H 12 ] 2- 、Tb-BCPI-1D、Tb-BCPI、B 12 H 12 @Comparison of the photoactivity of Tb-BCPI for CO2 reduction;

[0022] Figure 6 For B 12 H 12 @ Gas chromatogram collected during 2 hours of CO2 reduction by Tb-BCPI;

[0023] Figure 7 Ln-BCPI and B 12 H 12 Comparison chart of CO yield of @Ln-BCPI;

[0024] Figure 8 For recycling B 12 H 12 @Comparison of the photoactivity of Tb-BCPI in reducing CO2;

[0025] Figure 9 For B 12 H 12 Photocatalytic reduction on @Tb-BCPI 13 Mass spectra of CO2 products;

[0026] Figure 10 For B 12 H 12 XPS patterns of @Tb-BCPI in air and CO2 atmosphere;

[0027] Figure 11 For B 12 H 12 @Tb-BCPI, Tb-BCPI and closo-[B 12 H 12 ]2- Electron paramagnetic resonance images, a is the EPR spectrum of DMPO-·OH free radical capture, b is the EPR spectrum of DMPO-·O2 - EPR spectroscopy of free radical capture;

[0028] Figure 12 For B 12 H 12 @A comprehensive mechanistic pathway for CO2 reduction catalyzed by Tb-BCPI;

[0029] Figure 13 is the emission spectrum of BCPI after adding different amounts of TEOA into the ligand aqueous solution;

[0030] Figure 14 To add different amounts of closo-[B 12 H 12 ] 2- Emission spectrum of post-BCPI;

[0031] Figure 15 For TEOA and closo-[B 12 H 12 ] 2- IGMH diagrams of molecular interactions;

[0032] Figure 16 For closo-[B 12 H 12 ] 2- and in situ electron paramagnetic resonance images of BCPI under light and dark conditions;

[0033] Figure 17 For B 12 H 12 @Time-varying EPR spectra after irradiation of Tb-BCPI;

[0034] Figure 18 For [B 12 H 12 ] -· and BCPI · Molecular orbital diagram of

[0035] Figure 19 For closo-[B 12 H 12 ] 2- Participating B 12 H 12 @Tb-BCPI reaction diagram;

[0036] Figure 20 The data diagram of the electron transfer from the ligand to the metal is shown in Figure 1. a is a schematic diagram of the electron transfer from the BCPI ligand to the Tb metal, and b is a schematic diagram of the electron transfer from the B 12 H12 N spectrum of @Tb-BCPI in XPS under light or darkness, c is B 12 H 12 @Tb-BCPI Tb spectrum in XPS under light or darkness, d is the fs-TAS three-dimensional map of Gd-BCPI, e is the fs-TAS three-dimensional map of Tb-BCPI, f is B 12 H 12 @Tb-BCPI fs-TAS three-dimensional diagram, g is the fs-TAS excited state absorption contour diagram of Gd-BCPI, h is the fs-TAS excited state absorption contour diagram of Tb-BCPI, i is B 12 H 12 @Tb-BCPI fs-TAS excited state absorption contour map, j is Gd-BCPI fs-TAS excited state absorption contour map after 716fs, k is Tb-BCPI fs-TAS excited state absorption contour map after 716fs, l is B 12 H 12 @Tb-BCPI fs-TAS excited state absorption contour map after 716fs, m is the global analysis of fs-TAS raw data, n is B 12 H 12 @Schematic diagram of the sensitization pathways of Tb-BCPI, Tb-BCPI, and Gd-BCPI;

[0037] Figure 21 Tb 3+ Schematic diagram of the activation mechanism of CO2 adsorption on active sites;

[0038] Figure 22 For closo-[B 12 H 12 ] 2- , Tb-BCPI and B 12 H 12 CO2 adsorption-desorption isotherm of @Tb-BCPI;

[0039] Figure 23 For closo-[B 12 H 12 ] 2- , Tb-BCPI and B 12 H 12 Electrochemical reduction curve of @Tb-BCPI in CO2 atmosphere system;

[0040] Figure 24 For B 12 H 12 @Tb-BCPI, Tb-BCPI and closo-[B 12 H 12 ] 2-In situ DRIFT spectrum of gaseous CO2 / H2O mixture adsorbed under dark conditions for 60 minutes;

[0041] Figure 25 For B 12 H 12 @Tb-BCPI electron density map;

[0042] Figure 26 The structural scheme of the Tb site (CO2@Tb) after geometric optimization using the CASTEP module of Materials Studio software;

[0043] Figure 27 For B 12 H 12 Differential charge analysis of CO2 molecules adsorbed on @Tb-BCPI;

[0044] Figure 28 For B 12 H 12 @Tb-BCPI CO2 molecule adsorption diagram under different light exposure times;

[0045] Figure 29 For B 12 H 12 @Tb-BCPI CO2 conversion intermediates under light irradiation for 0 to 150 min;

[0046] Figure 30 For B 12 H 12 @Schematic diagram of the mechanism pathway of CO2 reduction reaction catalyzed by Tb-BCPI. DETAILED DESCRIPTION

[0047] Specific embodiment 1: This embodiment is a lanthanide metal organic framework, which is composed of {[Ln(BCPI)2(COO)(H2O)2]·H2O} n and closo-[B 12 H 12 ] 2- prepared;

[0048] The {[Ln(BCPI)2(COO)(H2O)2]·H2O} n Where n is 1 to 10, Ln is Tb, La, Ce, Sm, Eu or Er; the chemical formula of the lanthanide metal organic framework is [Ln2(BCPI)3(H2O)3(B6H6)3] n , where n = 1 to 10, and Ln is Tb, La, Ce, Sm, Eu or Er.

[0049] This embodiment provides an improved method for preparing Ln-MOFs, wherein the nano-scale active ingredient closo-[B 12 H 12 ] 2- As Ln-MOF is encapsulated in the pores of Ln-BCPI, closo-[B 12 H 12 ] 2- Acting as a nanorelay to promote the radical-assisted electron transfer (RAET) process between the organic ligands of Ln-MOF and the triethanolamine (TEOA) sacrificial agent; subsequently improving the charge transfer from the ligand to the metal within Ln-MOF; and Tb 3+ Acting as a catalytically active center to promote the intermediate process pathway of CO2 molecules.

[0050] It can be seen that this embodiment introduces the nano-scale active ingredient closo-[B 12 H 12 ] 2- By improving the structure and function of Ln-MOFs, this method can effectively enhance the internal electron density distribution and charge transfer efficiency, thereby significantly improving the selectivity and efficiency of Ln-MOFs in the photocatalytic reduction of carbon dioxide. In particular, the LMCT process is enhanced by introducing nanoscale electronic relays. This improvement not only solves the performance problems of existing technologies, but also provides a new Ln-MOF material with practical application value in the field of photocatalysis.

[0051] The beneficial effects of this embodiment are:

[0052] This embodiment selects closo-[B 12 H 12 ] 2- As a nanorelay. First, closo-[B 12 H 12 ] 2- As a highly symmetrical nanoscale ion cluster, it can be evenly dispersed in the pores of Ln-MOFs, preventing pore blockage and maintaining the integrity of the material structure. Secondly, the dodecaborane molecule carries two permanent negative charges (2e - ), which is conducive to the efficient electron transfer between the inside and outside, thus facilitating the supply of electrons. Finally, closo-[B 12 H 12 ] 2- The abundant hydrogen bond acceptor (or donor) sites in the closo-[B 12 H 12 ] 2-The clusters flow toward Ln-MOF, generating a synergistic effect inside Ln-MOF and promoting LMCT by changing the distribution of the electron cloud.

[0053] In this embodiment, single crystal diffraction is used to characterize the synthesized lanthanide metal organic framework [Ln2(BCPI)3(H2O)3(B6H6)3] n (B 12 H 12 @Ln-BCPI material) was structurally characterized and confirmed that B 12 H 12 The successful integration of nanorelays into Ln-MOF structures. 12 H 12 ] 2- It was first introduced into the Ln-MOF family and used as a photocatalyst for carbon dioxide reduction reaction.

[0054] This embodiment successfully obtains B 12 H 12 The crystal structure of @Ln-BCPI material was studied, and high efficiency and high selectivity of photocatalytic CO2-to-CO conversion were achieved in the presence of triethanolamine (TEOA). The mechanism shows that B 12 H 12 As a nanorelay, the LMCT of Ln-MOF is significantly enhanced, and the Ln center has excellent adsorption and activation capabilities for CO2. This work also illustrates how functional materials, Ln-MOF catalysts, and electron donors work synergistically in the photocatalytic CO2 reduction process. This embodiment provides insights into the rational design and development of advanced photocatalytic systems for artificial photosynthesis from the perspective of Ln-MOF modification.

[0055] Specific embodiment 2: This embodiment provides a method for preparing a lanthanide metal organic framework, which is carried out according to the following steps:

[0056] 1. Reconstitute {[Ln(BCPI)2(COO)(H2O)2]·H2O} n and closo-[B 12 H 12 ] 2- Dissolve in H2O and then stir at room temperature to obtain a reaction system;

[0057] The {[Ln(BCPI)2(COO)(H2O)2]·H2O} n Where n = 1 to 10, Ln is Tb, La, Ce, Sm, Eu or Er;

[0058] 2. Heating the reaction system at 90°C to 95°C for 72 to 120 hours, then cooling to room temperature, and finally centrifuging, washing, and drying to obtain a lanthanide metal-organic framework;

[0059] The chemical formula of the lanthanide metal organic framework is [Ln2(BCPI)3(H2O)3(B6H6)3] n , where n = 1 to 10, and Ln is Tb, La, Ce, Sm, Eu or Er.

[0060] {[Tb(BCPI)2(COO)(H2O)2]·H2O} described in step 1 n The preparation was specifically carried out with reference to the following literature: Zhao, S.-N. et al. Lanthanide ion codoped emitters for tailoring emissiontrajectory and temperature sensing. Adv. Funct. Mater. 25, 1463-1469 (2015).

[0061] The closo-[B 12 H 12 ] 2- The preparation was specifically carried out with reference to the following literature: Deng, X. et al. Atom-dispersed Au combined with nano-Au on halloysite nanotubes with closo-dodecaborate promotes synergistic effects for enhanced photocatalysis. J. Mater. Chem. A. 11, 809-817 (2023).

[0062] Specific embodiment three: This embodiment differs from the specific embodiment two in that: the {[Ln(BCPI)2(COO)(H2O)2]·H2O} in step one n With closo-[B 12 H 12 ] 2- The molar ratio is 1: (15-17); the {[Ln (BCPI) 2 (COO) (H 2 O) 2] · H 2 O} described in step 1 n The molar ratio of NH4Cl2 to H2O is 1 mmol: (300-400) mL. Other aspects are the same as those of the second embodiment.

[0063] Specific embodiment 4: This embodiment differs from specific embodiment 2 or 3 in that: in step 1, stirring is performed at room temperature and a stirring speed of 200 rpm to 500 rpm for 30 to 60 minutes. Other steps are the same as specific embodiment 2 or 3.

[0064] Specific embodiment 5: This embodiment differs from specific embodiments 2 to 4 in that the temperature is lowered to room temperature at a rate of 10°C / h to 15°C / h in step 2. The rest is the same as specific embodiments 2 to 4.

[0065] Specific embodiment 6: This embodiment differs from any one of specific embodiments 2 to 5 in that: the {[Ln(BCPI)2(COO)(H2O)2]·H2O} in step 1 n Specifically, it is prepared according to the following steps:

[0066] 1,3-bis(4-carboxyphenyl)imidazolium chloride and Ln(NO3)3·6H2O are mixed to obtain a mixture, the mixture is added to a mixed solvent of DMF and H2O and heated to react, and then naturally cooled to room temperature. Finally, the solid phase product is separated by centrifugation, washed, and dried to obtain {[Ln(BCPI)2(COO)(H2O)2]·H2O} n , wherein n=1-10, Ln is Tb, La, Ce, Sm, Eu or Er; Ln in the Ln(NO3)3·6H2O is Tb, La, Ce, Sm, Eu or Er. Other aspects are the same as those in specific embodiments 2 to 5.

[0067] Specific embodiment 7: This embodiment differs from specific embodiments 2 to 6 in that the molar ratio of 1,3-bis(4-carboxyphenyl)imidazolium chloride to Ln(NO3)3·6H2O is 1:(0.5-1). Other aspects are the same as specific embodiments 2 to 6.

[0068] Specific Embodiment 8: This embodiment differs from Specific Embodiments 2 to 7 in that the molar ratio of 1,3-bis(4-carboxyphenyl)imidazolium chloride to the volume ratio of the DMF and HO mixed solvent is 1 mmol:(20-35) mL; and the volume ratio of DMF to HO in the DMF and HO mixed solvent is 1:(0.5-1). Other aspects are the same as Specific Embodiments 2 to 7.

[0069] Specific embodiment 9: This embodiment differs from specific embodiments 2 to 8 in that the heating is performed at a temperature of 120° C. to 130° C. for 72 hours to 120 hours. Other aspects are the same as specific embodiments 2 to 8.

[0070] Specific embodiment 10: This embodiment uses a lanthanide metal organic framework as a photocatalyst for carbon dioxide reduction.

[0071] The following examples are used to verify the beneficial effects of the present invention:

[0072] Example 1:

[0073] A method for preparing a lanthanide metal-organic framework is carried out according to the following steps:

[0074] 1. Reconstitute {[Tb(BCPI)2(COO)(H2O)2]·H2O} n (10 mg, 0.012 mmol) and closo-[B 12 H 12 ] 2- (80 mg, 0.1962 mmol) was dissolved in 4 mL of H2O, and then stirred at room temperature and 500 rpm for 30 min to obtain a reaction system;

[0075] The {[Tb(BCPI)2(COO)(H2O)2]·H2O} n n = 1;

[0076] Second, the reaction system was heated at 95°C for 120 hours, then cooled to room temperature at a rate of 10°C / hour, and finally centrifuged, washed with distilled water multiple times, and dried to obtain a lanthanide metal-organic framework.

[0077] The chemical formula of the lanthanide metal organic framework is [Tb2(BCPI)3(H2O)3(B6H6)3] n , where n=1, abbreviated as B 12 H 12 @Tb-BCPI.

[0078] {[Tb(BCPI)2(COO)(H2O)2]·H2O} described in step 1 n Specifically, it is prepared according to the following steps:

[0079] 1,3-Bis(4-carboxyphenyl)imidazolium chloride (0.0517 g, 0.15 mmol) and Tb(NO3)3·6H2O (0.0453 g, 0.1 mmol) were mixed to obtain a mixture, which was added to a mixed solvent of 3 mL of DMF and 1.5 mL of H2O, heated at 120°C for 120 h, and then naturally cooled to room temperature. The solid phase product was separated by centrifugation, washed several times with a mixed solvent of DMF and H2O (the volume ratio of DMF to H2O was 2:1), and finally dried under vacuum at 60°C for 12 h to obtain {[Tb(BCPI)2(COO)(H2O)2]·H2O} n , abbreviated as Tb-BCPI-1D.

[0080] If Tb(NO3)3·6H2O is replaced by La(NO3)3·6H2O, Ce(NO3)3·6H2O, Sm(NO3)3·6H2O, Eu(NO3)3·6H2O or Er(NO3)3·6H2O, B can be obtained. 12 H 12 @La-BCPI, B 12 H 12 @Ce-BCPI, B 12 H 12 @SmBCPI, B 12 H 12 @Eu-BCPI or B 12 H 12 @Er-BCPI.

[0081] The unified abbreviation is B 12 H 12 @Ln-BCPI, Ln is Tb, La, Ce, Sm, Eu or Er. Other aspects are the same as those in the first embodiment.

[0082] In this example, the organic ligand 1,3-bis(4-carboxyphenyl)imidazolium chloride (BCPI) was purchased from a chemical reagent company (China) and used without further purification. Tb(NO₃)₃·6H₂O and the anhydrous solvent DMF were purchased from HWRK Chemical Company (China) and used without further purification.

[0083] Table 1: B 12 H 12 Crystallographic parameters of @Tb-BCPI

[0084]

[0085]

[0086] In the table, R1=∑(||F o |-|Fc ||) / ∑|F o |;wR2={∑[w(F o 2 -F c 2 )] / ∑[w(F o 2 )] 2} 1 / 2 .

[0087] Figure 1 Tb-BCPI-1D and B 12 H 12 @Tb-BCPI structure comparison diagram; As can be seen from the figure, in order to achieve high charge transfer efficiency and directional electron transfer pathway, a cationic skeleton was designed using a positively charged 1,3-bis(4-carboxyphenyl)imidazolium chloride (BCPI) ligand. Tb with a 4f multi-electron layer was selected. 3+ The photocatalytic host material was synthesized, which is characterized by an unsaturated coordination environment and a unique behavior as a charge transfer bridge. 3+ The assembly between ions and H2BCPI ligands synthesized a one-dimensional (1D) chain lanthanide coordination polymer Tb-BCPI-1D, which could not obtain multidimensional and porous MOF materials. In addition, the selection of closo-[B 12 H 12 ] 2- As a facilitator of charge transfer in Ln-MOF, it has Unique sub-nanometer size, stable 2e - The electronic configuration and abundant hydrogen bond acceptor (or donor) sites make it an ideal electronic relay ( Figure 2 For closo-[B 12 H 12 ] 2- ). The closo-[B 12 H 12 ] 2- By reacting with Tb-BCPI-1D, a two-dimensional (2D) layered lanthanide organic framework was successfully obtained, named B 12 H 12 @Tb-BCPI (Table 1). X-ray single crystal diffraction analysis showed that there are two closo-[B 12 H 12 ] 2- Cluster, and closo-[B 12 H 12 ] 2- Forms multiple dihydrogen bonds (BH δ- ···H δ+ -C)( Figure 1 The middle part is enlarged in detail), rather than directly with Tb 3+ ions or Tb-O nodes interact. In this two-dimensional Ln-MOFs, the central Tb 3+ The ion exhibits a slightly distorted 12-sided geometry with eight coordination sites. The adjacent BCPI ligand and Tb 3+ The ion orientation angles are 134.41° and 45.58°, respectively, forming a Rhombus channel extending along the a-axis. closo-[B 12 H 12 ] 2- It plays a key role in the formation of two-dimensional porous Ln-MOFs. 12 H 12 ] 2- It is a structural director for Ln-MOFs crystallization, ensuring the electrostatic balance of cationic lattice charges.

[0088] Figure 3 For B 12 H 12 @Tb-BCPI thermogravimetric analysis diagram; As can be seen from the figure, between 100℃ and 300℃, the material will lose mass, which is mainly due to the volatilization of adsorbed water and solvent molecules. Then between 300℃ and 500℃, the material will decompose significantly, which is mainly due to the decomposition reaction of organic ligands. 12 H 12 @Tb-BCPI is thermally stable.

[0089] For comparison, B was removed. 12 H 12 @Tb-BCPI and B 12 H 12 @M-BCPI in closo-[B 12 H 12 ] 2- ions, through B 12 H 12 The molecular exchange between @Tb-BCPI and solvent was used to prepare the same two-dimensional metal organic framework (Tb-BCPI and M-BCPI). The specific preparation method is as follows: 10mgB 12 H 12@Tb-BCPI was dissolved in 10 mL of a 3:7 acetic acid / water solution, sonicated for 2 hours, and then centrifuged to collect the solid. The collected solid was then dissolved in 10 mL of a 4:6 acetic acid / water solution, sonicated for another 2 hours, and centrifuged to collect the solid again. This process was repeated with increasing acetic acid ratios (5:5, 6:4, 7:3, 8:2, and 9:1) until the final solution was 10 mL of pure acetic acid. After each sonication and centrifugation cycle, the collected solid was dissolved in fresh solution for the next treatment. Finally, the collected solid was dried in a vacuum oven at 60°C for 24 hours to obtain the final solid, Tb-BCPI. Powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR) analysis demonstrated that the structural integrity of the Tb-BCPI framework was maintained.

[0090] Under simulated sunlight, triethanolamine (TEOA) was used as a sacrificial electron donor and proton source (without photosensitizer) to photocatalytically reduce carbon dioxide in water. The specific process was as follows: 0.005 g of powder sample (closo-[B 12 H 12 ] 2- , Tb-BCPI-1D, Tb-BCPI or B 12 H 12 @Tb-BCPI) was dispersed in a mixed solution of water (5 mL) and triethanolamine (1 mL) and then placed in a 120 mL cylindrical steel reactor. High-purity CO2 gas (99.9%) was then introduced into the reactor to reach ambient pressure. Under simulated sunlight (300 W xenon lamp with a wavelength of 320-780 nm), 5 mL of the gas mixture was withdrawn from the reactor at regular intervals. The CO concentration was analyzed using a gas chromatograph with an FID (with a CO2 converter), and the H2 concentration was analyzed using a TCD detector (GC-7980, Techcomp) equipped with a thermal conductivity detector, 5 angstrom molecular sieves, and an Ar carrier. 12 H 12 The photocatalytic stability of @Tb-BCPI was studied by performing five consecutive cycles of evacuating and refilling with carbon dioxide. The cyclic tests were conducted according to the same procedure, with each run lasting 4 hours. After each run, the spent photocatalyst was separated, rinsed with copious amounts of water, and then dried in a vacuum oven at 80°C before the next cycle. Any catalyst lost during the cycle was replaced with fresh catalyst. The performance test results are as follows:

[0091] It is worth noting that in the absence of sacrificial agents, the photocatalytic performance of the sample is almost non-existent. Compared with other sacrificial agents, triethanolamine shows a stronger electron donor ability and significantly improves the reduction efficiency of carbon dioxide.12 H 12 The solution after Tb-BCPI reduced CO2 was filtered with a 0.4μm filter membrane, and the filtered liquid was subjected to liquid chromatography analysis, which proved that no new product was generated in the solution after the reaction; 12 H 12 In the @Tb-BCPI sample, CO was the main product of the photocatalytic reduction of CO2, with a yield of 110.3 μmol g -1 h -1 , no CH4 or liquid products were detected ( Figure 4 For B 12 H 12 @Liquid chromatogram of the solution after Tb-BCPI reduced CO2); Figure 5 For closo-[B 12 H 12 ] 2- 、Tb-BCPI-1D、Tb-BCPI、B 12 H 12 @Tb-BCPI photoactivity comparison chart for CO2 reduction; As can be seen from the figure, B 12 H 12 The selectivity of the @Tb-BCPI sample was greater than 99% (99.2%). In the comparative experiment, the CO2 yields of the photocatalysts Tb-BCPI-1D and Tb-BCPI were quite low (0.8 μmol g -1 h -1 and 1.0 μmol g -1 h -1 ). Under the same conditions, the best B 12 H 12 The carbon dioxide photoconversion efficiency of @Tb-BCPI (110.3 μmol g -1 h -1 ) were 110.3 times and 137.8 times that of Tb-BCPI-1D and Tb-BCPI, respectively. Figure 6 For B 12 H 12 @ Gas chromatogram collected during 2 hours of CO2 reduction by Tb-BCPI;

[0092] Table 2: B 12 H 12 @Tb-BCPI collects 2 hours of gas chromatography raw data during CO2 reduction

[0093]

[0094] Figure 7 Ln-BCPI and B 12 H 12Comparison of CO yield of @Ln-BCPI; As can be seen from the figure, the introduction of closo-[B 12 H 12 ] 2- It is also applicable to other lanthanide metals such as La, Ce, Sm, Eu and Er, while B 12 H 12 The modified Tb composite material showed the best photoactivity.

[0095] Figure 8 For recycling B 12 H 12 Comparison of the photoactivity of Tb-BCPI in reducing CO2. As shown in the figure, the first yield is 380.76 μmol g -1 , second yield: 384.55 μmol g -1 , the third yield: 382.26 μmol g -1 , the fourth yield: 378.42 μmol g -1 , the fifth yield: 372.89 μmol g -1 In the second and third runs, the photocatalytic activity remained essentially unchanged.

[0096] In B 12 H 12 @Tb-BCPI photocatalyst 13 C-Labeled CO2 photoreduction. Figure 9 For B 12 H 12 Photocatalytic reduction on @Tb-BCPI 13 The product mass spectrum of CO2. In the gas chromatography-mass spectrometry, a small peak was observed at m / z=29, which was attributed to 13 CO. These evidences suggest that the evolutionary products do originate from 13 Photoreaction of CO2.

[0097] Through B 12 H 12 @Tb-BCPI was subjected to UV-visible diffuse reflectance spectroscopy and Mott-Schottky measurements to clarify the band structure of the material, thereby verifying its performance advantages in photocatalytic applications and further illustrating that B 12 H 12 Feasibility of @Tb-BCPI materials for CO2 reduction.

[0098] Through time-resolved fluorescence decay kinetics studies, it was found that closo-[B 12 H 12 ] 2- The introduction of Tb 3+The fluorescence decay lifetime was extended from 746.02μs (Tb-BCPI) to 798.49μs (B 12 H 12 @Tb-BCPI), which shows that closo-[B 12 H 12 ] 2- Enhanced BCPI to Tb 3+ This prolonged fluorescence decay lifetime suggests that Tb 3+ It may play a key role in the CO2 adsorption process. 12 H 12 @Tb - Tb in BCPI 3+ To further confirm this hypothesis, the adsorption sites were analyzed using XPS under a CO2 atmosphere. Figure 10 For B 12 H 12 XPS patterns of @Tb-BCPI in air and CO2 atmosphere; the shift of the Tb 4d peak in the spectrum indicates that Tb may form a stable Tb-CO2 complex through chemical interaction, thereby serving as an active site for chemical adsorption.

[0099] Compared with Tb-BCPI alone, the electronegativity of closo-[B 12 H 12 ] 2- Connected to the cationic two-dimensional Tb-BCPI framework, it can enrich B 12 H 12 The electronic structure and photonic properties of @Tb-BCPI were analyzed by transient photocurrent density and electrochemical impedance spectroscopy; the results showed that closo-[B 12 H 12 ] 2- The presence of reduces carrier recombination and facilitates the LCMT process of photogenerated carriers.

[0100] In addition, to confirm the charge transfer mechanism, electron paramagnetic resonance (EPR) measurements were performed under the conditions of a power of 500 W, a wavelength of 365 nm, and an illumination time of 5 min; Figure 11 For B 12 H 12 @Tb-BCPI, Tb-BCPI and closo-[B 12 H 12 ] 2- Electron paramagnetic resonance images, a is the EPR spectrum of DMPO-·OH free radical capture, b is the EPR spectrum of DMPO-·O2 - EPR spectrum of free radical capture; the results show that B 12 H 12@Tb-BCPI has a higher EPR response compared to Tb-BCPI, indicating more efficient charge separation.

[0101] Kelvin probe measurements show that WF(closo-[B 12 H 12 ) 2- ) < WF(Tb-BCPI), which indicates that electrons are more inclined to escape from closo-[B 12 H 12 ) 2- and transfer to Tb-BCPI at the B 12 H 12 @Tb-BCPI interface. These results suggest that adding closo-[B 12 H 12 ) 2- to regulate the local pore environment of Ln-MOFs can significantly enhance LMCT, thereby improving the photocatalytic efficiency. In addition, the performance comparison before and after the introduction of closo-[B 12 H 12 ) 2- also indicates that closo-[B 12 H 12 ) 2- may interact with TEOA as a nano-relay, further promoting electron transfer. Based on these experimental results and theoretical analyses, a comprehensive mechanistic pathway for the efficient photocatalytic reduction of CO2 by B 12 H 12 @Tb-BCPI is proposed; Figure 12 For the comprehensive mechanistic pathway of the B 12 H 12 @Tb-BCPI-catalyzed CO2 reduction reaction; First, under light illumination, B 12 H 12 U@Tb-BCPI initiates the photocatalytic reaction, BCPI plays the role of absorbing light energy, and transfers its excited electrons to the Tb oxygen cluster through LMCT; Second, closo-[B 12 H 12 ) 2- acts as an electron relay, transferring its own electrons and the electrons supplemented from TEOA to the BCPI ligand to promote the reaction; Finally, the active site Tb 3+ completes the photocatalytic reaction.

[0102] Gradually add an aqueous solution of triethanolamine (TEOA) with a concentration of 10 -2 mol / L or closo-[B 12 H 12 ) 2-aqueous solution, so that the solution of TEOA or closo-[B 12 H 12 ] 2- The concentration of BCPI was 0-12 mM, and then the fluorescence of BCPI with TEOA or closo-[B 12 H 12 ] 2- The interaction between them. Figure 13 is the emission spectrum of BCPI after adding different amounts of TEOA into the ligand aqueous solution; Figure 14 To add different amounts of closo-[B 12 H 12 ] 2- The emission spectrum of BCPI after addition of TEOA; under light excitation, BCPI will quickly return from the excited state to the ground state and produce fluorescence at 425nm; the fluorescence spectrum shows that the fluorescence intensity of BCPI decreases slightly after the addition of TEOA, which may be due to the influence of water. At 0.8mM, the fluorescence intensity tends to be stable, indicating that the stabilizing effect of TEOA on BCPI is negligible, indicating that the interaction between TEOA and BCPI is not obvious. On the contrary, the addition of closo-[B 12 H 12 ] 2- After the addition of TEOA, the fluorescence intensity of BCPI increased significantly, which was due to the electron transfer from TEOA to BCPI. This preliminarily verified that in the photocatalytic system, there was no direct interaction between TEOA and BCPI, but it might be through closo-[B 12 H 12 ] 2- Mediated electron transport mechanism.

[0103] Figure 15 For TEOA and closo-[B 12 H 12 ] 2- IGMH diagram of molecular interactions; the iso value is 0.004 au, and the density functional theory (DFT) was used to calculate the molecular interactions between triethanolamine (TEOA) and closo-[B 12 H 12 ] 2- The interaction of closo-[B 12 H 12 ] 2- The green area indicates the interaction region between closo-[B 12 H 12 ]2- The weak interactions between TEOA and closo-[B 12 H 12 ] 2- There is a significant electrostatic interaction (ESP) between the two, which promotes the 12 H 12 ] 2- The electron transfer to BCPI effectively enhances the stability and sustainability of the electron transfer process.

[0104] XPS was used to further observe the 12 H 12 @Tb-BCPI B1s peak binding energy changes, found that the introduction of closo-[B 12 H 12 ] 2- After that, its binding energy moves toward the high field direction, indicating that the electrons move from closo-[B 12 H 12 ] 2- However, due to the closo-[B 12 H 12 ] 2- Keeping 2e - The remarkable characteristics of closo-[B 12 H 12 ] 2- In situ electron paramagnetic resonance of BCPI under simulated sunlight (wavelength 365nm, power 500W mercury lamp) and dark conditions. Figure 16 For closo-[B 12 H 12 ] 2- and BCPI in situ electron paramagnetic resonance images under light and dark conditions; As can be seen from the figure, closo-[B 12 H 12 ] 2- Both BCPI and closo-[B 12 H 12 ] 2- The signal of closo-[B 12 H 12 ] 2-and BCPI to generate free radicals, and the presence of free radicals will facilitate the electron transfer process between the two. Specifically, the g factor of free electrons is approximately equal to 2.0023, and closo-[B 12 H 12 ] 2- The EPR signal g value of BCPI is about 2.0037, which further proves the generation of free radicals.

[0105] Test the B under simulated sunlight (wavelength 365nm, power 500W mercury lamp) 12 H 12 Time-varying EPR spectrum of @Tb-BCPI. Figure 17 For B 12 H 12 Time-dependent EPR spectra of @Tb-BCPI after irradiation; With the extension of illumination time, the EPR signal intensity gradually increases, especially reaching the maximum intensity at 60 minutes. This time-dependent signal enhancement further supports the hypothesis of free radical generation and electron transfer. The amount of free radical generation increases with the increase of illumination time, indicating that closo-[B 12 H 12 ] 2- and BCPI promote electron transfer through a free radical pair mechanism under light conditions.

[0106] The test was conducted under simulated sunlight (wavelength 365nm, power 500W mercury lamp), 12 H 12 @The EPR spectrum of triethanolamine (TEOA) added to the Tb-BCPI system; 12 H 12 After adding TEOA to the @Tb-BCPI system, the EPR signal of the sample almost completely disappeared, indicating that TEOA effectively captured and neutralized free radicals as a free radical scavenger. The electron supplementation of TEOA eliminated the free radical signal, which further verified the closo-[B 12 H 12 ] 2- The interaction between BCPI and TEOA is achieved through free radical-assisted electron transfer. The introduction of TEOA blocks this process, resulting in the disappearance of free radical signals. The redox potential of the reaction can explain this phenomenon: 12 H 12 @Tb-BCPI has a low oxidation potential (E vB (B 12 H 12 @Tb-BCPI)=1.47V vs.RHE), TEOA is easily 12 H 12Photoinduced hole oxidation to TEOA in @Tb-BCPI + (E(TEOA / TEOA + )=1.10V vs.RHE), resulting in electron release, followed by deprotonation of the cation TEOA to form aldehyde. 12 H 12 @Tb-BCPI undergoes a photoinduced electron transfer process under light. Specifically, electrons are transferred from closo-[B 12 H 12 ] 2- transfer to BCPI, thereby forming a free radical pair (B 12 H 12 -· andBCPI · ). When BCPI further undergoes LMCT, the electrons generated by TEOA oxidation will further replenish closo-[B 12 H 12 ] 2- Nanorelay. Mulliken spin density analysis shows that the spin density (green) in closo-[B 12 H 12 ] 2- and BCPI + The total density of these two molecules is 1, indicating that the generation of a diradical pair is theoretically possible.

[0107] Figure 18 For [B 12 H 12 ] -· and BCPI · Molecular orbital diagram; obtained through molecular orbital (MO) calculation, after light excitation, BCPI is excited to the excited state BCPI · , intermolecular electron transfer from closo-[B 12 H 12 ] 2- The SOMO orbital (-2.08 eV) of BCPI is transferred to the SOMO-1 orbital (-6.81 eV) of BCPI.

[0108] Figure 19 For closo-[B 12 H 12 ] 2- Participating B 12 H 12 @Tb-BCPI reaction diagram; in B 12 H 12 @Tb-BCPI photoexcitation, closo-[B 12 H 12 ] 2-The nanorelay and the ligand underwent an electron transfer cooperative free radical reaction, and TEOA provided electronic support for a stable system cycle.

[0109] Figure 20 The data diagram of the electron transfer from the ligand to the metal is shown in Figure 1. a is a schematic diagram of the electron transfer from the BCPI ligand to the Tb metal, and b is a schematic diagram of the electron transfer from the B 12 H 12 N spectrum of @Tb-BCPI in XPS under light or darkness, c is B 12 H 12 @Tb-BCPI Tb spectrum in XPS under light or darkness, d is the fs-TAS three-dimensional map of Gd-BCPI, e is the fs-TAS three-dimensional map of Tb-BCPI, f is B 12 H 12 @Tb-BCPI fs-TAS three-dimensional diagram, g is the fs-TAS excited state absorption contour diagram of Gd-BCPI, h is the fs-TAS excited state absorption contour diagram of Tb-BCPI, i is B 12 H 12 @Tb-BCPI fs-TAS excited state absorption contour map, j is Gd-BCPI fs-TAS excited state absorption contour map after 716fs, k is Tb-BCPI fs-TAS excited state absorption contour map after 716fs, l is B 12 H 12 @Tb-BCPI fs-TAS excited state absorption contour map after 716fs, m is the global analysis of fs-TAS raw data, n is B 12 H 12 @Schematic diagram of the sensitization pathways of Tb-BCPI, Tb-BCPI, and Gd-BCPI;

[0110] In order to further study the closo-[B 12 H 12 ] 2- The photoinduced LMCT process (Figure a) was investigated, and the mechanism information was collected from in situ XPS and femtosecond transient absorption spectroscopy (fs-TAS). In situ XPS spectra showed that under light irradiation (wavelength 370 nm, power 300 W xenon lamp), B 12 H 12 @Tb - Tb from BCPI 4 d 5 / 2 The peak of N1s shifts significantly toward lower binding energy (Fig. c), while the peak of N1s shifts toward higher binding energy (Fig. b); this indicates that electrons are transferred from BCPI to Tb during the catalytic reaction. 3+ , where the photogenerated electrons flow to the latter for reducing CO2. In the process of photocatalytic reduction of CO2, closo-[B 12 H12 ] 2- It is thought to accelerate the LMCT process, thereby generating active sites in Tb-oxo clusters.

[0111] In order to determine the mechanism and excited state dynamics energy transfer, fs-TAS experiments were conducted to study B by 425 nm visible light excitation. 12 H 12 The transient absorption spectrum of @Tb-BCPI sample was obtained. However, after analysis, it was found that the entire dynamic process could not be fully described. Therefore, 320 nm ultraviolet light excitation was used to obtain the B 12 H 12 @Tb-BCPI, Tb-BCPI and its Gd 3+ The complete spectrum of the analogue (Gd-BCPI, the preparation process is exactly the same as that of Tb-BCPI, only Tb(NO3)3·6H2O is replaced by Gd(NO3)3·6H2O) is provided for subsequent analysis (Figure df); 3+ Due to the lack of energetically accessible excited 4f levels in the ion, Gd-BCPI can be used to study excited-state dynamics in the absence of energy transfer. The observed spectra all include an excited-state absorption (ESA) spectrum with a peak at approximately 385 nm and a relatively broad ESA feature between 430 nm and 500 nm. These signals rapidly evolve into a long-lasting feature with a peak at approximately 450 nm. Because ligand-based electronic transitions are being probed, a decay of the excited ESA is observed, coinciding with the growth of the ESA (Figure g). The ESA of Gd-BCPI blue-shifts beyond the data acquisition window by 7.3 ns, while the similar ESA of Tb decays rapidly to the ground state within 1 ns, suggesting rapid energy transfer (Figure h). This spectral feature further confirms the transfer of electrons from the ligand BCPI to the coordinated terbium metal node, as the ESA signal in Tb-BCPI shows a fairly rapid decay, reflecting the electron transfer process.

[0112] Further research on B 12 H 12 @Tb-BCPI system closo-[B 12 H 12 ] 2- The kinetic behavior of Tb-BCPI and the obvious ESA signal was observed in the wavelength range of 330-550 nm. 12 H 12The positive signal of @Tb-BCPI at 384nm comes from the excited state absorption of the singlet state, and the weak positive signal at 454nm comes from the excited state absorption of the triplet state (Figure i). Similar excited state absorption peaks are also observed at 380nm and 452nm for Tb-BCPI. The decay process of the excited state is further analyzed, and the time evolution of ESA after 716fs is compared (Figure jl). It is worth noting that the absorption peak at 456nm corresponding to the triplet state Gd-BCPI has a longer decay time and lasts until 7ns before returning to the baseline. Obviously, B 12 H 12 @Tb-BCPI shows a faster single-line decay signal than Tb-BCPI. At 109ps, Tb-BCPI has not fully recovered to the baseline, while B 12 H 12 @Tb-BCPI is close to the baseline, which indicates that the electron transfer rate is fast.

[0113] To further explore the evolution of excited states, a global analysis of the femtosecond TAS raw data was performed. The decay-related difference spectra (DADS) of Gd-BCPI and Tb-BCPI respectively showed two exponential components: the short-lived component corresponds to the first singlet excited state (S1) of the ligand, and the second component corresponds to the first triplet excited state (T1; Figure m). The T1 lifetime of Tb-BCPI (157.9ps) obtained by lifetime fitting differs by three orders of magnitude from the T1 lifetime of Gd-BCPI (8.7ns), which clearly reveals the evolution of the ligand from T1 to Tb. 3+ Therefore, these results clearly indicate the photoexcitation dynamics of the Tb-BCPI system. 12 H 12 The global fitting analysis of @Tb-BCPI also reveals a double exponential decay pattern. The results of the double exponential fitting are τ1 = 148.2 fs and τ2 = 294.4 ps. Compared with τ1 of Tb-BCPI, B 12 H 12 The surface state electron lifetime (τ1) of @Tb-BCPI is significantly shortened to 148.2fs. This obvious kinetic acceleration indicates that closo-[B 12 H 12 ] 2- and Tb-BCPI interface. 12 H 12 The τ2 exciton lifetime of @Tb-BCPI is much longer than that of pure Tb-BCPI, which should be attributed to the effective spatial separation leading to a longer exciton relaxation process, which means that the photogenerated carriers have more opportunities to participate in the photocatalytic reaction.

[0114] According to the above kinetic process, in Gd-BCPI, the energy transfer path is the absorption transition from the BCPI ground state S0 to S1, followed by the intersystem conversion (ISC) of S1→T1. 3+ The 4f excited state (4f*) has a high energy level and cannot undergo T1 energy transfer, resulting in the T1 energy transition to the ground state S0. In Tb-BCPI, B 12 H 12 @Tb-BCPI Since the triplet energy is rarely observed, this suggests that BCPI shows a tendency toward Tb in the singlet state. 3+ The rapid charge transfer is beneficial to the energy transfer to Tb 3+ The excited state energy levels of the ions determine the main energy acquisition pathway for charge transfer from S1 to 4f* (Figure n).

[0115] Figure 21 Tb 3+ Schematic diagram of the activation mechanism of CO2 adsorption at active sites; as can be seen from the figure, Tb is used as a catalytic site to activate and reduce carbon dioxide (CO2) to carbon monoxide (CO) through the LMCT process.

[0116] The sample to be tested (B 12 H 12 @Tb-BCPI, Tb-BCPI and closo-[B 12 H 12 ] 2- ) is prepared into a uniform powder or granular form of 100 mg, the sample is placed in a vacuum and set to a specific treatment temperature to remove gas and moisture adsorbed on the surface, and then the sample is placed in an adsorption instrument with a liquid nitrogen temperature set to 77.35K. The adsorption isotherm is measured by gradually increasing the gas (CO2) pressure; Figure 22 For closo-[B 12 H 12 ] 2- , Tb-BCPI and B 12 H 12 CO2 adsorption-desorption isotherm of @Tb-BCPI. CO2 adsorption-desorption isotherm shows that B 12 H 12 @Tb-BCPI Maximum CO2 adsorption: 7.41572 cm 3 / g; Tb-BCPI: 4.2964cm 3 / g;closo-[B 12 H 12 ] 2- :1.9786cm 3 / g;B 12 H 12@Tb-BCPI has a stronger adsorption capacity, which is due to the Tb-oxo site and closo-[B 12 H 12 ] 2- The adsorption interaction of molecules is improved.

[0117] Electrochemical (EC) reduction measurements were performed in a conventional three-electrode system. 12 H 12 @Tb-BCPI, Tb-BCPI and closo-[B 12 H 12 ] 2- A thin film electrode was prepared as the working electrode. The specific preparation method was as follows: 0.1 g of sample was mixed with 1 mL of naphthol (Nafion:ethanol volume ratio = 1:9) and sonicated for 1 hour to prepare the desired solution. This solution was then dropped onto an ITO conductive glass and spin-coated using a spin coater at a specific speed. The film thickness was adjusted by controlling the spin coating speed (2000 rpm) and time (30 seconds). A platinum plate (99.9%) and a silver / silver chloride electrode served as the counter and reference electrodes, respectively. A 0.1 M solution of 1-butyl-3-methylimidazolium hexafluorophosphate in dichloromethane was used as the electrolyte. High-purity CO₂ (99.999%) was bubbled into the electrolyte before and during the experiments. The electrochemical performance of a series of catalysts was tested using an IVIUM V13806 electrochemical workstation. All experiments were conducted at room temperature. Figure 23 For closo-[B 12 H 12 ] 2- , Tb-BCPI and B 12 H 12 The electrochemical reduction curve of @Tb-BCPI in CO2 atmosphere system. The electrochemical reduction curve further shows that B 12 H 12 :-1.01V; Tb-BCPI:-0.91V; B 12 H 12 @Tb-BCPI:-0.82V; B 12 H 12 @Tb-BCPI exhibits a low reduction potential in a CO2 environment, indicating its excellent catalytic activity for CO2 reduction.

[0118] The sample is placed in a sample holder with a flat surface. A lid is fixed on the sample holder to form a reaction space. The reaction space is then purged with argon gas, and DRIFTS data is collected as a background. Subsequently, carbon dioxide is introduced through a container filled with water, allowing the gas to bring water into the reaction space. DRIFTS data is then collected over time to record changes based on DRIFTS. Figure 24 For B 12 H12 @Tb-BCPI, Tb-BCPI and closo-[B 12 H 12 ] 2- In situ DRIFT spectrum of adsorption of gaseous CO2 / H2O mixture for 60 minutes under dark conditions; DRIFTS analysis showed that B 12 H 12 @Tb-BCPI increases the adsorption of CO2 at 2359 cm -1 and 2339cm -1 There is an obvious absorption peak at the position, which is caused by the asymmetric stretching vibration of CO2, while Tb-CO2 - The complex is at 1655cm -1 There is a significant absorption peak at 12 H 12 ] 2- After adsorption enhancement.

[0119] Figure 25 For B 12 H 12 The electron density map of @Tb-BCPI; As can be seen from the figure, the electron density difference comes from B 12 H 12 @Tb-Atomic closo-[B in BCPI 12 H 12 ] 2- There is a significant negatively charged region within the unit, located at the center of the Tb-BCPI pore, which is beneficial for CO2 enrichment and improves the photocatalytic activity compared with Tb-BCPI.

[0120] Figure 26 The structural scheme of the Tb site (CO2@Tb) after geometry optimization using the CASTEP module of Materials Studio software is shown. The bond lengths of Tb-C and hydrogen bonds are given. DFT simulations illustrate the relationship between carbon dioxide and B 12 H 12 Competitive adsorption behavior on the active sites of @Tb-BCPI. After adsorption, carbon dioxide 12 H 12 ] 2- The structure is linear, the bond angle is 177.06°, and the BC bond length is In contrast, in Tb 3+ The adsorption at the CO2 bond angle is reduced to 115.59° and the Tb-C bond length is reduced to This indicates that this is a chemical adsorption mechanism. 12 H 12 ] 2-The physical adsorption mechanism and Tb 3+ The difference in chemical adsorption mechanisms highlights the differences in selectivity and reversibility. Computational modeling further compared the stability of Tb adsorbed carbon dioxide with and without molecularly coordinated water, and the results showed that the latter was more stable.

[0121] Figure 27 For B 12 H 12 Differential charge analysis of CO2 molecules adsorbed on @Tb-BCPI. The charge density difference reveals the electron transfer kinetics between CO2 and Tb, supporting CO2 activation. Furthermore, hydrogen bonding between CO2 and the coordinated water on Tb enhances CO2 adsorption, benefiting from the unique microenvironment created by the adsorbed CO2.

[0122] To elucidate the details of the chemical bonds, in situ Fourier transform infrared spectroscopy was used to identify potential intermediates throughout the reaction process. The sample was loaded into a flat sample holder, and a lid was fixed to the sample holder to form a reaction space. The reaction space was then purged with argon gas, and DRIFTS data was collected as a background. Visible light (500W power, wavelength 320-780nm) was then introduced into the reaction space through an observation window. Carbon dioxide was introduced through a container filled with water, allowing the gas to carry water into the reaction space. DRIFTS data was then collected over time to record changes based on DRIFTS. 12 H 12 @Tb-BCPI was subjected to dark conditions for up to 60 min without any additional vibrational peaks being observed. Figure 28 For B 12 H 12 @Tb-BCPI CO2 molecule adsorption diagram under different light exposure times; after irradiation, CO2 molecules are adsorbed at 3598, 3626, 3705 and 3728 cm -1 The adsorption peak (ν3(CO2)) gradually decreases, indicating that CO2 has begun to be converted. Figure 29 For B 12 H 12 @Tb-BCPI CO2 conversion intermediates under irradiation for 0 to 150 minutes; after irradiation for 0 to 150 minutes, B 12 H 12 1532cm appeared on @Tb-BCPI -1 and 1699cm -1 These peaks correspond to the formation of *COOH, 1426 cm -1 HCO3 - The symmetrical stretching of indicates the co-adsorption of CO2 and H2O, and the other monodentate carbonate and carboxylate peaks further demonstrate the dynamic adsorption and conversion process.

[0123] Established B 12 H 12 The Gibbs energy evaluation model of the intermediate products in the photocatalytic process of @Tb-BCPI reveals the CO2 photoreduction process from a molecular perspective. *The formation of COOH is the decisive step in the reduction of CO2 to CO, and in B 12 H 12 The energy barrier in @Tb-BCPI is only 0.06 eV, which is much lower than many previously reported MOF-based catalysts. This may be attributed to the interaction of COOH* with surface Tb 2+ Furthermore, the downslope free energy curve of protonation of *COOH to *CO indicates that B 12 H 12 @Tb-BCPI is spontaneously converted, and the Gibbs free energy of CO hydrogenation shows that the energy of generating *CHO (ΔG(*CHO)) is higher than the desorption energy of CO molecules. This means that B 12 H 12 @Tb-BCPIs favor the desorption of *CO from their surfaces rather than the protonation of *CO to produce *CHO, which explains their nearly 100% selectivity for light-driven CO2 reduction to CO.

[0124] Figure 30 For B 12 H 12 @Schematic diagram of the mechanism of CO2 reduction reaction catalyzed by Tb-BCPI; Based on the above data, a possible reaction pathway is given. The photocatalytic process begins with the excitation of the ligand, closo-[B 12 H 12 ] 2- Acting as a nanorelay, it transfers electrons from TEOA and itself to the ligand. Subsequently, these electrons are transferred to Tb via LMCT. 3+ , forming the thermodynamically favorable Tb 2+ Active center. In the first step, Tb 2+ The center binds to CO2 and stabilizes it by forming hydrogen bonds with coordinated water molecules (a). This suggests that the hydroxyl groups in the coordinated water microstructure can provide accessible protons to CO2 molecules, thereby promoting hydrogen-assisted CO2 reduction. Subsequently, the protons from the hydroxyl groups on the coordinated water will spontaneously react with CO2 to form BCPI-Tb 2+ It should be noted that the carbon atom in CO2 carries a positive charge, which helps it pass through Tb 2+ Partially attract electrons (c). The coordinated water is in a proton-deficient state and can spontaneously capture protons generated during water oxidation to form a stable BCPI-Tb 3+Based on the above, the adsorbed CO2 molecules have been successfully hydrogenated to COOH*(d), which can be further reduced to CO through a hydrogen-assisted process. In the next step, the BCPI ligand accepts the closo-[B 12 H 12 ] 2- The transferred electrons then undergo LMCT to form BCPI-Tb 2+ -HOH-COOH*. The coordinated water provides protons, which are then incorporated into BCPI-Tb 2+ -HO-COOH2*(e). Next, BCPI-Tb 2 + The intermediate product of -HO-COOH2* after further protonation and subsequent water elimination leads to BCPI-Tb 2+ -HOH-COO*(f). In the last step, BCPI-Tb 2+ -HOH-COO* is regenerated by subsequent reduction and CO removal, thereby re-entering the catalytic cycle.

Claims

1. A lanthanide metal-organic framework, characterized in that Lanthanide metal-organic frameworks are composed of {[Ln(BCPI)2(COO)(H2O)2]·H2O} n and closo-[B 12 H 12 ] 2- prepared; The {[Ln(BCPI)2(COO)(H2O)2]·H2O} n Where n is 1 to 10, Ln is Tb, La, Ce, Sm, Eu or Er; the chemical formula of the lanthanide metal organic framework is [Ln2(BCPI)3(H2O)3(B6H6)3] n , where n = 1 to 10, and Ln is Tb, La, Ce, Sm, Eu or Er.

2. The method for preparing a lanthanide metal-organic framework according to claim 1, wherein It is carried out in the following steps:

1. Reconstitute {[Ln(BCPI)2(COO)(H2O)2]·H2O} n and closo-[B 12 H 12 ] 2- Dissolve in H2O and then stir at room temperature to obtain a reaction system; The {[Ln(BCPI)2(COO)(H2O)2]·H2O} n Where n = 1 to 10, Ln is Tb, La, Ce, Sm, Eu or Er; 2. Heating the reaction system at 90°C to 95°C for 72 to 120 hours, then cooling to room temperature, and finally centrifuging, washing, and drying to obtain a lanthanide metal-organic framework; The chemical formula of the lanthanide metal organic framework is [Ln2(BCPI)3(H2O)3(B6H6)3] n , where n = 1 to 10, and Ln is Tb, La, Ce, Sm, Eu or Er.

3. The method for preparing a lanthanide metal-organic framework according to claim 2, characterized in that {[Ln(BCPI)2(COO)(H2O)2]·H2O} described in step 1 n With closo-[B 12 H 12 ] 2- The molar ratio is 1: (15-17); the {[Ln (BCPI) 2 (COO) (H 2 O) 2] · H 2 O} described in step 1 n The molar volume ratio of to H2O is 1mmol:(300~400)mL.

4. The method for preparing a lanthanide metal-organic framework according to claim 2, characterized in that In step 1, the mixture is stirred at room temperature and a stirring speed of 200 rpm to 500 rpm for 30 min to 60 min.

5. The method for preparing a lanthanide metal organic framework according to claim 2, characterized in that In step 2, the temperature is lowered to room temperature at a rate of 10°C / h to 15°C / h.

6. The method for preparing a lanthanide metal-organic framework according to claim 2, characterized in that {[Ln(BCPI)2(COO)(H2O)2]·H2O} described in step 1 n Specifically, it is prepared according to the following steps: 1,3-bis(4-carboxyphenyl)imidazolium chloride and Ln(NO3)3·6H2O are mixed to obtain a mixture, the mixture is added to a mixed solvent of DMF and H2O and heated to react, and then naturally cooled to room temperature. Finally, the solid phase product is separated by centrifugation, washed, and dried to obtain {[Ln(BCPI)2(COO)(H2O)2]·H2O} n , wherein n=1-10, Ln is Tb, La, Ce, Sm, Eu or Er; in the Ln(NO3)3·6H2O, Ln is Tb, La, Ce, Sm, Eu or Er.

7. The method for preparing a lanthanide metal-organic framework according to claim 6, characterized in that The molar ratio of the 1,3-bis(4-carboxylphenyl)imidazolium chloride to Ln(NO3)3·6H2O is 1:(0.5-1).

8. The method for preparing a lanthanide metal-organic framework according to claim 6, characterized in that The volume ratio of the mole of the 1,3-bis(4-carboxyphenyl)imidazolium chloride to the mixed solvent of DMF and H2O is 1 mmol:(20-35) mL; the volume ratio of DMF to H2O in the mixed solvent of DMF and H2O is 1:(0.5-1).

9. The method for preparing a lanthanide metal-organic framework according to claim 6, characterized in that Heat at a temperature of 120°C to 130°C for 72h to 120h.

10. The use of a lanthanide metal organic framework according to claim 1, characterized in that It is used as a photocatalyst for carbon dioxide reduction.

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