Photocatalyst as well as preparation method and application thereof

Abstract

The invention discloses a photocatalyst as well as a preparation method and application thereof. The photocatalyst is prepared from aminated MXene, a COFs (Covalent Organic Frameworks) material and a rhodium atom catalyst, the aminated MXene and the COFs material are connected through a covalent bond; rhodium atoms in the rhodium atom catalyst are connected with the COFs material through an N-Rh bond. The aminated MXene and COFs materials are combined with the rhodium atom catalyst, on one hand, the rhodium atom catalyst is connected through an N-Rh bond to improve the electron transfer efficiency, and the NADH regeneration capacity is more efficient; on the other hand, aminated MXene is added to be combined with COFs, and efficient coenzyme regeneration is achieved by means of the excellent conductivity of MXene. The photocatalyst disclosed by the invention is coupled with FDH enzyme, so that light-enzyme cascade catalytic reaction can be realized.

Description

Technical Field

[0001] The present invention relates to the field of photocatalysis technology, and in particular to a photocatalyst and a preparation method and application thereof. Background Art

[0002] With the rapid development of global industrialization and urbanization, excessive emissions of carbon dioxide (CO2) have caused numerous environmental problems. In recent years, numerous researchers have conducted research in the fields of photocatalysis, electrocatalysis, and thermocatalysis to convert CO2 into high-value chemicals. The CO2 reduction reaction involves multiple proton-coupled electron transfers and reaction intermediates, resulting in low selectivity for the target product. Enzymatic catalysis, such as formate dehydrogenase (FDH), is used to efficiently and specifically convert CO2 into formic acid. However, in the CO2 reduction process, nicotinamide adenine dinucleotide (NADH) is required as a coenzyme to stimulate the redox properties of FDH. However, the high price of NADH (approximately US$2,600 per mole) limits the direct use of the coenzyme NADH for catalysis. Therefore, the construction of an efficient NADH regeneration system is of great significance.

[0003] However, existing photocatalysts have the problems of low charge transfer efficiency and low coenzyme regeneration efficiency. Therefore, it is necessary to develop a photocatalyst with high charge transfer efficiency and high coenzyme regeneration efficiency. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, in a first aspect, the present invention provides a photocatalyst that has high charge transfer efficiency and high coenzyme regeneration efficiency, and can couple with FDH to achieve a light-enzyme cascade reaction to promote CO2 reduction.

[0005] The second aspect of the present invention also provides a method for preparing a photocatalyst.

[0006] The third aspect of the present invention also provides an application of a photocatalyst in NADH regeneration.

[0007] The fourth aspect of the present invention further provides an application of a photocatalyst in catalytic reduction of formic acid with carbon dioxide.

[0008] According to the first aspect of the present invention, a photocatalyst is provided, comprising an amino-modified MXene, a COFs material and a rhodium atom catalyst; the amino-modified MXene and the COFs material are connected by a covalent bond; and the rhodium atom in the rhodium atom catalyst and the COFs material are connected by an N-Rh bond.

[0009] According to a preferred embodiment of the present invention, the rhodium atoms account for 0.1 wt.% to 1 wt.% of the total mass of the photocatalyst, calculated based on the total mass of the photocatalyst. For example, the range includes 0.1 wt.%, 0.107 wt.%, 0.431 wt.%, 0.630 wt.%, 0.633 wt.%, 1 wt.%, or any subrange between these two values.

[0010] According to a preferred embodiment of the present invention, the content of the aminated MXene is 10 wt.% to 25 wt.%, calculated based on the total weight of the aminated MXene and the COFs material, for example, including 10 wt.%, 15 wt.%, 20 wt.%, 25 wt.%, or a subrange between any two of these values.

[0011] According to a preferred embodiment of the present invention, the amino MXene comprises amino Ti3C2T x .

[0012] According to a preferred embodiment of the present invention, the amino Ti3C2T x Prepared by the following method:

[0013] 1. Take hydrofluoric acid and Ti3AlC2 powder in a polytetrafluoroethylene beaker and stir to remove the Al layer of Ti3AlC2. Centrifuge the suspension and rinse thoroughly with deionized water to obtain layered Ti3C2T under dry conditions. x , and collect the resulting black powder. Then take the layered Ti3C2T x Add to a beaker containing tetramethylammonium hydroxide solution (TMAOH), divide into centrifuge tubes, centrifuge and collect the supernatant, wash the remaining suspension with deionized water and centrifuge to ensure that the layered Ti3C2T x It can be fully separated, finally filtered, freeze-dried and collected to obtain Ti3C2T x nanosheets;

[0014] 2. Obtained Ti3C2T x The nanosheets were dissolved in a mixture of 3-aminopropyltriethoxysilane (APTES), ethanol and ultrapure water and stirred at room temperature. They were then washed with ethanol solution, filtered and freeze-dried to obtain the amino-modified Ti3C2T x .

[0015] According to a preferred embodiment of the present invention, the COFs material includes at least one of porphyrin-based COFs, bipyridyl-based COFs, iminopyridine COFs or triazine COFs.

[0016] According to a preferred embodiment of the present invention, the porphyrin-based COFs are prepared from 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (HTAPP) and 2,2'-bipyridine-5,5'-dialdehyde.

[0017] According to a preferred embodiment of the present invention, the bipyridyl COFs are prepared by using an aldehyde bipyridyl monomer and an aminoporphyrin monomer.

[0018] According to a preferred embodiment of the present invention, the iminopyridine COFs are prepared from triazine triphenylamine monomers and 2,6-pyridinedicarboxaldehyde monomers.

[0019] According to a preferred embodiment of the present invention, the triazine COFs are prepared from triazine triphenylamine monomers and 1,3,5-trialdehyde benzene monomers.

[0020] According to a preferred embodiment of the present invention, the rhodium atom catalyst includes at least one of a rhodium complex (Cp*RhCl2)2, rhodium nanoparticles, Rh2O3, and RhCl3.

[0021] The photocatalyst according to the embodiment of the present invention has at least the following beneficial effects:

[0022] This invention combines aminated MXene, COFs, and a rhodium atom catalyst. On the one hand, the rhodium atom catalyst is connected via an N-Rh bond to improve electron transfer efficiency, resulting in more efficient NADH regeneration. On the other hand, the addition of aminated MXene to the COFs utilizes MXene's excellent conductivity to achieve efficient coenzyme regeneration. The coupling of this photocatalyst with the FDH enzyme enables a light-enzyme cascade catalytic reaction.

[0023] Furthermore, the photocatalyst of the present invention can not only improve the NADH regeneration activity, but also improve the selectivity of 1,4-NADH.

[0024] According to a second aspect of the present invention, there is provided a method for preparing the photocatalyst according to the first aspect of the present invention, comprising the following steps:

[0025] S1. Mixing monomers for preparing COFs materials, amino-modified MXene materials, catalysts, and solvent I by ultrasonication; degassing by freezing-evacuating-thawing cycles of liquid nitrogen for several times, and then heating and reacting under vacuum conditions to obtain intermediate I;

[0026] S2, mixing the intermediate I, the rhodium atom catalyst and the solvent II, stirring and reacting to obtain the product.

[0027] According to a preferred embodiment of the present invention, the amino MXene material is prepared by the following method:

[0028] The MXene material, 3-aminopropyltriethoxysilane and solvent III are mixed and stirred to obtain the amino-modified MXene material.

[0029] According to a preferred embodiment of the present invention, in step S1, the catalyst includes at least one of acetic acid, p-toluenesulfonic acid, and toluene.

[0030] According to a preferred embodiment of the present invention, in step S1, the temperature of the heating reaction is 100-130°C.

[0031] According to a preferred embodiment of the present invention, in step S1, the heating reaction time is 24 to 96 hours.

[0032] According to a preferred embodiment of the present invention, the solvent I comprises acetonitrile and dioxane.

[0033] According to a preferred embodiment of the present invention, the solvent II includes at least one of methanol, DMF, n-butanol, and o-dichlorobenzene.

[0034] According to a preferred embodiment of the present invention, in step S2, the stirring speed is 100-150 r / min.

[0035] A third aspect of the present invention provides a use of the above-mentioned photocatalyst in the regeneration of nicotinamide adenine dinucleotide (NADH).

[0036] A fourth aspect of the present invention provides a use of the above-mentioned photocatalyst in catalytic reduction of formic acid with carbon dioxide.

[0037] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments with reference to the following drawings, in which:

[0039] Figure 1 Schematic diagram of the preparation process of the photocatalyst according to an embodiment of the present invention;

[0040] Figure 2 1. It is a structural representation diagram of the photocatalyst of the embodiment of the present invention and the comparative example;

[0041] Figure 3 are SEM and TEM images of the photocatalysts of the embodiments of the present invention and the comparative examples;

[0042] Figure 4are the UV-visible diffuse reflectance spectra and Tauc plots of the photocatalysts of the embodiments of the present invention and the comparative examples;

[0043] Figure 5 NADH regeneration rate diagram of the photocatalysts of the embodiment of the present invention and the comparative example;

[0044] Figure 6 1 is a diagram showing the yield and reaction mechanism of the catalytic reduction of formic acid by carbon dioxide using the photocatalysts of the examples of the present invention and the comparative example. DETAILED DESCRIPTION

[0045] The following are specific embodiments of the present invention, and the technical solutions of the present invention are further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0046] Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0047] The raw materials used in the examples of the present invention and the comparative examples are as follows:

[0048] Preparation of amino-modified MXene:

[0049] 100 mL of hydrofluoric acid (49 wt%) and 2.0 g of Ti3AlC2 powder were placed in a polytetrafluoroethylene beaker and stirred at 60 ° C for one day to remove the Al layer of Ti3AlC2. The suspension was centrifuged and thoroughly rinsed with deionized water to obtain layered Ti3C2T under dry conditions. x , and the resulting black powder was collected. Then 160 mg of layered Ti3C2T x The suspension was added to a beaker containing 20 mL of tetramethylammonium hydroxide solution (TMAOH, 25 wt%), divided into 10 mL centrifuge tubes, centrifuged at 8000 rpm for 30 min, and the supernatant was collected. The remaining suspension was washed with deionized water and centrifuged 2-3 times to ensure that the layered Ti3C2T x It can be fully separated, finally filtered, freeze-dried and collected to obtain Ti3C2T x Nanosheets.

[0050] The obtained Ti3C2T x The nanosheets were dissolved in a mixture of 200 μL 3-aminopropyltriethoxysilane (APTES), 3 mL ethanol, and 24 mL ultrapure water and stirred at room temperature for 24 hours. The solution was then rinsed 4-5 times with 50% ethanol solution. The amination of Ti3C2T was obtained by filtration and freeze-drying. x (Named: NH2-Ti3C2T x ).

[0051] Rhodium atom catalysts: rhodium complexes (Cp*RhCl2)2 and [Cp*Rh(bpy)(H2O)] 2+ . Where [Cp*Rh(bpy)(H2O)] 2+ It is prepared by mixing (Cp*RhCl2)2 and 2,2-bipyridine and configured into a 5mmol / L solution.

[0052] In the following examples of the present invention, "anchored (Cp*RhCl2)2" refers to the formation of N-Rh bonds between rhodium and COFs. "Homogeneous [Cp*Rh]" refers to the physical mixing of rhodium with PBC or MXPBC without forming chemical bonds.

[0053] Example 1

[0054] This example provides a photocatalyst, including amino-modified MXene, COFs material and rhodium atom catalyst; the amino-modified MXene and COFs material are connected by covalent bonds; the rhodium atom in the rhodium atom catalyst and the COFs material are connected by N-Rh bonds. The preparation diagram is shown in the figure below. Figure 1 As shown, the steps are as follows:

[0055] S1. A Schlenk tube was charged with 13.5 mg of catalyst monomer 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (HTAPP) and 8.5 mg of 2,2'-bipyridine-5,5'-dialdehyde (BPYD), 4.2 mg of NH2-Ti3C2T x , as well as 0.5mL acetonitrile solution and 0.5mL dioxane, and finally 0.1mL acetic acid solution (6mol / L) was added as a catalyst; after ultrasonic treatment for 30 minutes, the Schlenk tube was quickly frozen under liquid nitrogen. After three freeze-pump-thaw cycles of degassing, it was vacuumed and sealed, and then heated at 120°C for 72 hours. The resulting powder was thoroughly washed with DMF, tetrahydrofuran, and acetone, and then vacuum dried at 100°C overnight; intermediate I (named MX 20 PBC).

[0056] S2. Add 10 mg of MX into the beaker. 20 PBC, 15 mL methanol and 3.5 g L -1 (Cp*RhCl2)2 was stirred for 24 hours, transferred to a shaker at a speed of 120 r / min, and vacuum dried at 60 ° C overnight to obtain a photocatalyst (named MX 20 PBC-Rh 3.5 ; The proportion of rhodium element is 0.630wt.%).

[0057] According to the preparation process of step S1, by controlling the addition of different contents of NH2-Ti3C2Tx , different intermediates I can be obtained. For example, by adding 1.8 mg, 3.0 mg and 5.4 mg respectively, intermediates I (named successively: MX 10 PBC、MX 15 PBC and MX 25 PBC).

[0058] Example 2

[0059] This example provides a photocatalyst, and its preparation method is the same as that of Example 1, except that the concentration of (Cp*RhCl2)2 in step S2 is 0.5 g L -1 ; Prepared photocatalyst (named: MX 20 PBC-Rh 0.5 ; The proportion of rhodium element is 0.107wt.%).

[0060] Example 3

[0061] This example provides a photocatalyst, and its preparation method is the same as that of Example 1, except that the concentration of (Cp*RhCl2)2 in step S2 is 2.0 g L -1 ; Prepared photocatalyst (named: MX 20 PBC-Rh2; the proportion of rhodium element is 0.431wt.%).

[0062] Example 4

[0063] This example provides a photocatalyst, and its preparation method is the same as that of Example 1, except that the concentration of (Cp*RhCl2)2 in step S2 is 5.0 g L -1 ; Prepared photocatalyst (named: MX 20 PBC-Rh 5.0 ; The proportion of rhodium element is 0.633wt.%).

[0064] Comparative Example 1

[0065] This example provides a photocatalyst (named: PBC), the preparation method of which is as follows:

[0066] A Schlenk tube was charged with 13.5 mg of the catalyst monomer, 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (HTAPP) and 8.5 mg of 2,2'-bipyridine-5,5'-dialdehyde (BPYD). 0.5 mL of acetonitrile solution and 0.5 mL of dioxane were added, followed by 0.1 mL of 6 mol / L acetic acid solution as a catalyst. After 30 minutes of sonication, the Schlenk tube was rapidly frozen in liquid nitrogen. After degassing through three freeze-pump-thaw cycles, the tube was evacuated and sealed, then heated at 120°C for 72 hours. The resulting powder was thoroughly washed with DMF, tetrahydrofuran, and acetone, then dried in vacuo at 100°C overnight to yield PBC.

[0067] Comparative Example 2

[0068] Comparative Example 2 provides a photocatalyst (named MX 20 PBC), the preparation method is the same as that of Example 1, except that step S2 is missing.

[0069] Comparative Example 3

[0070] Comparative Example 3 provides a photocatalyst (named MX 20 PBC+[Cp*Rh]), whose composition is MX 20 PBC and homogeneous electron mediator [Cp*Rh(bpy)(H2O)] 2+ (0.0612mmol L -1 ) is a mixture of

[0071] Similarly, MX can also be prepared 10 PBC+[Cp*Rh]、MX 15 PBC+[Cp*Rh]、MX 25 PBC+[Cp*Rh].

[0072] Comparative Example 4

[0073] Comparative Example 4 provides a photocatalyst (named PBC+[Cp*Rh]), which is composed of PBC and a homogeneous electron mediator [Cp*Rh(bpy)(H2O)] 2+ (0.0612mmol L -1 ) is a mixture of

[0074] Comparative Example 5

[0075] Comparative Example 5 provides a photocatalyst (named: PBC-Rh 3.5 ), the preparation method is the same as that of Example 1, except that NH2-Ti3C2T is not added in step S1. x .

[0076] Performance Testing

[0077] First, XRD, FTIR and CP / MAS were used 13 The PBC COF synthesized in Comparative Example 1 was characterized by C-NMR. Figure 2 As shown, Figure 2 a is the XRD pattern of PBC; PBC has a strong diffraction peak at 3.0°, belonging to the (110) crystal plane, and three weak diffraction peaks at 3.8°, 6.0° and 25.3°, belonging to the (020), (220) and (001) crystal planes respectively. The crystal structure can be simulated by Pawley orbitals, and the unit cell parameters are Rp and Rwp are 3.92% and 3.11%, respectively, indicating that the experimental simulation results are in good agreement with the AA stacking pattern. In the FTIR spectrum ( Figure 2 b), PBC at 1619 cm -1 The C=N stretching vibration band is shown at the same time as the -CHO stretching vibration band of BPYD (1695cm -1 ) and the -NH2 vibration band of HTAPP (3205cm -1 and 3348cm -1 ) was significantly attenuated, indicating that HTAPP and BPYD synthesized PBC through Schiff base reaction. 13 C NMR spectroscopy Figure 2 c. The α-pyrrole carbon present in HTAPP shows a peak at 147.2 ppm (2), and the signal of β-pyrrole carbon appears at 113.4 ppm (1, 3). The peaks from 130.4 to 133.7 ppm (4, 5, 6, 7) are derived from the phenylene carbon of the HTAPP unit. The resonance peaks at 121.6 ppm, 120.3 ppm, and 153.2 ppm all belong to the pyridine carbon (9, 10, 11, 12) in the BPYD unit; the signal at 157.2 ppm (8) corresponds to the formation of the C=N bond between HTAPP and BPYD, which further verifies the successful synthesis of PBC.

[0078] The XRD spectrum of MXene prepared by the present invention is as follows Figure 2 As shown in d, after Ti3AlC2 is etched, the peak of the (104) crystal plane at 39.0° disappears completely, and then after peeling, the multilayer Ti3C2T x The (002) crystal plane at 8.9° shifted to 6.1°, and after further amination, NH2-Ti3C2T x The (002) crystal plane appears at 5.6°, which indicates that the interlayer spacing of MXene is wider. x After mixing, MX aThe XRD spectra of PBC (a = 10, 15, 20, 25) are as follows Figure 2 As shown in e, MX a The three peaks of PBC at 3.0°, 5.6° and 25.3° correspond to the (110) crystal plane of PBC, NH2-Ti3C2T x The (002) crystal plane of MXene and the (001) crystal plane of PBC. As the mass ratio of MXene increases, the strength of the PBC (110) plane decreases, even in the case of 20 PBC and MX 25 No longer observed in PBC. 20 After anchoring (Cp*RhCl2)2 on the PBC basis (photocatalysts prepared in Examples 1 to 4), the XRD patterns did not change significantly, indicating that the introduction of (Cp*RhCl2)2 did not destroy the MX 20 The structure of PBC Figure 2 f).

[0079] Furthermore, the photocatalysts prepared in the examples and comparative examples were subjected to XPS tests, and the results were as follows: Figure 2 As shown in g, 2h, 2i and 2j, the C1s of PBC of Comparative Example 1 ( Figure 2 g) Three signals respond at 288.1eV, 286.2eV and 284.8eV, respectively, belonging to -C=N, -CN and -CC (C=C) bonds. 20 PBC and MX 20 PBC-Rh 3.5 The C1s spectrum of Ti3C2T includes all the signals found in PBC and a new signal appears at 281.2 eV, which can be assigned to -C-Ti. x Successfully combined with PBC. In the N1s XPS spectrum ( Figure 2 h), the three binding energies of PBC COF at 399.7eV, 398.9eV and 397.9eV correspond to the imine nitrogen, pyrrole nitrogen and pyridinic nitrogen signals respectively. 20 PBC-Rh 3.5 (43.3%) and MX 20 The imine nitrogen content of PBC (43.2%) is much higher than that of PBC (34.8%), which is due to the x A -C=N bond is formed between MX and PBC. 20 PBC-Rh 3.5 A new N1s binding energy peak was observed at 398.2 eV, which was attributed to the N-Rh formed by the coordination of the Rh complex with the nitrogen atom on the bipyridine structure. Figure 2 i), MX20 PBC and MX 20 PBC-Rh 3.5 The spectrum of MX has four double peaks (Ti 2p3 / 2-2p1 / 2), with a fixed area ratio of 2:1 and a double peak spacing of 5.7eV. 20 PBC-Rh 3.5 The Rh 3d signal can be observed in Figure 2 j), to demonstrate the immobilization of (Cp*RhCl2)2.

[0080] Furthermore, the morphology and microstructure of the photocatalysts prepared in the examples of the present invention and the comparative examples were further observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The PBC of comparative example 1 exhibited a cluster structure consisting of stacked fragments ( Figure 3 a, 3d), while NH2-Ti3C2T x Presents a smooth layered structure ( Figure 3 b). Due to NH2-Ti3C2T x The amino groups of PBC cross-link with the aldehyde groups of PBC, promoting the formation of PBC in NH2-Ti3C2T x The effective growth on the PBC. Figure 3 e) The lattice fringes with a width of 0.67 nm belonging to PBC can be clearly seen, corresponding to the (001) plane of PBC. 20 TEM image of PBC ( Figure 3 f) The morphologies of MXene and PBC are observed simultaneously. Further zooming in reveals a clear interface between the two ( Figure 3 g), lattice fringes with spacings of 1.00 nm and 0.67 nm can be observed on both sides of the interface, which are attributed to NH2-Ti3C2T x The (002) crystal plane of the photocatalyst MX prepared in Example 1 of the present invention and the (001) crystal plane of the PBC. 20 PBC-Rh 3.5 The uniform distribution of C, N, Ti, Rh, and Cl elements can be observed in the element mapping image to verify the [Cp*Rh] 20 Successful fixation on PBC ( Figure 3 h).

[0081] Furthermore, the absorption and band structure of the photocatalyst were studied by UV-visible diffuse reflectance spectroscopy and Mott-Schottky plot. Figure 4 As shown in a, all photocatalysts exhibit multiple absorption peaks in the UV-visible diffuse reflectance spectra due to the strong light absorption ability of the porphyrin units on the PBC COF. 20 PBC and MX20 PBC-Rh 3.5 The absorption edges of PBC and NH2-Ti3C2T show a slight red shift, which is attributed to the x The π-conjugated skeleton increases after binding. The Kubelka-Munk function is used to estimate PBC and MX 20 PBC, PBC-Rh 3.5 and MX 20 PBC-Rh 3.5 The band gaps (Eg) of the two electrodes are 2.06V, 2.01V, 1.98V and 1.95V respectively. The flat band potential (approximately equal to the conduction band potential (Eg)) was measured based on the Mott-Schottky plot. CB ) position), from Figure 4 As shown in b~4e, PBC, MX 20 PBC, PBC-Rh 3.5 and MX 20 PBC-Rh 3.5 E CB The potentials are -1.45, 1.52, -1.54 and -1.63 V (relative to Ag / AgCl, pH=6.5). According to the formula, at pH=0, PBC, MX 20 PBC, PBC-Rh 3.5 and MX 20 PBC-Rh 3.5 E CB Equal to -0.87V, -0.94V, -0.96V and -1.05V respectively. CB and Eg to calculate the valence band of the photocatalyst (E VB ) position, the band structure diagram is as follows Figure 4 f. Obviously, the E CB Shows the ratio [Cp*Rh] (-0.65V) and NAD + / NADH (-0.54 V) is more negative, while the E VB The oxidation potential is more positive than that of TEOA (0.83 V), indicating that all photocatalysts can reduce NAD + and oxidizes TEOA.

[0082] Furthermore, electrochemical impedance spectroscopy (EIS) Figure 4 As shown in g, it reflects that PBC has the largest semicircle radius, that is, the largest charge transfer resistance (R CT , 139 kΩ). Through the improved strategy of loading MXene or anchoring [Cp*Rh], MX 20 PBC and PBC-Rh 3.5 The EIS semicircle radius of the photocatalyst decreases, R CTThe values are 110kΩ and 46kΩ respectively. 20 PBC-Rh 3.5 R CT The value is further reduced to 33kΩ, and in the transient photocurrent test ( Figure 4 h), and PBC-Rh 3.5 (0.024μAcm -2 ) and MX 20 PBC (0.014 μA cm -2 ) compared to MX 20 PBC-Rh 3.5 (0.052 μA cm -2 ) showed excellent photocurrent response, even better than PBC (0.002 μA cm -2 ) is 25 times higher. Figure 4 As shown in Figure 1, the fluorescence lifetimes of the photocatalysts measured by time-resolved fluorescence spectroscopy (TRFS) are 1.13 ns, 1.56 ns, 1.78 ns, and 2.12 ns, respectively. This observation suggests that loading MXene or anchoring [Cp*Rh] can suppress the recombination of photogenerated electron-hole pairs, thereby extending the charge lifetime.

[0083] 1. NADH regeneration reaction

[0084] The photocatalysts prepared in the examples of the present invention and the comparative examples were used for NADH regeneration reaction, and the test steps were as follows:

[0085] A 300W xenon lamp equipped with a UV cutoff filter (λ>420nm) was used as the light source. The irradiation distance was 9.0cm. 10mg of the photocatalyst was added to 10mL of phosphate buffer (pH=7) containing 15%wt of TEOA sacrificial agent, 0.5mmol L -1 NAD + Under nitrogen protection and constant temperature control at 15°C, the reaction was shaded and samples were taken every 30 minutes. The samples were wrapped with tin foil and filtered. The supernatant was diluted 10 times and its absorbance at 340 nm was measured. The NADH yield of the photocatalyst was calculated using the NADH standard curve.

[0086] The results are as follows Figure 5 As shown in Figure 2, in the absence of [Cp*Rh], the NADH regeneration rate of PBC reached 34.8% within two and a half hours. After the introduction of homogeneous [Cp*Rh] into the reaction system, the NADH regeneration rate of PBC increased to 64.7%. Subsequently, a series of NADH regeneration experiments were carried out to obtain the NADH regeneration rate of Ti3C2T in the photocatalyst. x The optimal amount of Figure 5 As shown in a, in the absence of [Cp*Rh], as NH2-Ti3C2Tx The increase in MX a The NADH regeneration activity of PBC first increased and then decreased. x The best NADH regeneration activity was shown when the mass reached 20% (a=20). The order of NADH regeneration activity was MX 20 PBC (56.9%) > MX 25 PBC (53.2%) > MX 15 PBC (48.8%) > MX 10 PBC (41.2%). Meanwhile, in the presence of homogeneous [Cp*Rh], MX 20 PBC also achieved the best NADH regeneration activity (87.7%). This indicates that the combination of PBC and an appropriate amount of MXene can improve the NADH regeneration efficiency, while an excessive amount of MXene will reduce its NADH regeneration efficiency.

[0087] Different contents of (Cp*RhCl2)2 were anchored on the preferred MXene / COF catalyst MX 20 On PBC, it is represented as MX 20 PBC-Rh b (b=0.5, 2.0, 3.5, 5.0), the actual mass fraction of anchored Rh was measured by ICP-OES. Figure 5 As shown in b, as the amount of (Cp*RhCl2)2 increased from 0.5 g L -1 Increased to 3.5 g L -1 , the actual fixed Rh content increased from 0.107 wt% to 0.633 wt%. When the concentration of (Cp*RhCl2)2 increased from 3.5 g L -1 Further increase to 5.0 g L -1 When the content of coordinated Rh (from 0.630wt% to 0.633wt%) is changed, it is almost unchanged, indicating that the bipyridine structure has been coordinated and saturated. 20 PBC-Rh b The NADH regeneration activity of the cellulose acetate gel also increased with the increase of b value. When b = 3.5, its NADH regeneration activity reached the highest level, which was 97.1%.

[0088] Subsequently, in order to further study the effect of [Cp*Rh] on its NADH regeneration performance, the effects of [Cp*Rh]-free, homogeneous [Cp*Rh] (represented as +[Cp*Rh] in the figure) and anchored [Cp*Rh] on PBC and MX 20 The effect of PBC on catalytic performance. Among them, the anchoring [Cp*Rh] takes the optimal anchoring amount of Rh, that is, PBC-Rh 3.5 and MX 20 PBC-Rh3.5 .like Figure 5 As shown in c, the NADH regeneration rates of PBC without [Cp*Rh], homogeneous [Cp*Rh] and anchored [Cp*Rh] reached 34.8%, 64.7% and 72.7%, respectively. 20 The NADH regeneration rate of PBC in these three cases reached 56.9%, 87.7% and 97.1%, respectively. The detailed order of NADH yield of the four solid photocatalysts is MX 20 PBC-Rh 3.5 >PBC-Rh 3.5 >MX 20 PBC>PBC. It is consistent with the photoelectrochemical properties of the photocatalyst and is inversely proportional to the exciton binding energy of the catalyst ( Figure 4 fi). This indicates that the MX constructed by the double modification strategy 20 PBC-Rh 3.5 The NADH regeneration performance was synergistically improved by reducing the exciton binding energy.

[0089] like Figure 5 As shown in d, the NADH regeneration rates of PBC without [Cp*Rh], homogeneous [Cp*Rh], and anchored [Cp*Rh] were 69.7 μmol g -1 h -1 , 129.5 μmol g -1 h -1 and 145.5 μmol g -1 h -1 After loading MXene, MX 20 The NADH regeneration rate of PBC increased to 114.0 μmol g under the conditions of [Cp*Rh]-free, homogeneous [Cp*Rh], and anchored [Cp*Rh], respectively. -1 h -1 , 175.4 μmol g -1 h -1 and 194.1 μmol g -1 h -1 This indicates that regardless of the presence of [Cp*Rh], MX 20 The NADH regeneration rate of PBC is better than that of pure PBC, indicating that MXene as an electron mediator can effectively improve the NADH regeneration performance. 20 The order of NADH regeneration rate for PBC catalysts is anchored [Cp*Rh] > homogeneous [Cp*Rh] > no [Cp*Rh]. This indicates that the immobilized [Cp*Rh] strategy can shorten the charge transfer path and improve NADH regeneration activity compared with homogeneous [Cp*Rh].

[0090] In addition, if Figure 5 As shown in e, the comparison of kinetic constants (k) shows that the k values of PBC without [Cp*Rh], homogeneous [Cp*Rh] and fixed [Cp*Rh] are 0.249, 0.497 and 0.547, respectively. 20 The k values of PBC increased to 0.424, 0.686, and 0.989 under these three conditions, respectively. 20 PBC-Rh 3.5 The photocatalyst reached 0.989, which is 3.97 times that of pure PBC (0.249). At the same time, the selectivity of 1,4-NADH in the NADH regeneration reaction was further measured. Figure 5 f. The order of 1,4-NADH selectivity of PBC is anchored [Cp*Rh] (80.4%) > homogeneous [Cp*Rh] (74.3%) > no [Cp*Rh] (29.1%). After loading MXene, MX 20 The selectivity of PBC increased to 89.5%, 83.3%, and 68.5% under the conditions of anchored [Cp*Rh], homogeneous [Cp*Rh], and no [Cp*Rh], respectively. This indicates that loading MXene and anchoring [Cp*Rh] not only improve NADH regeneration activity but also increase the selectivity of 1,4-NADH, which is beneficial for the subsequent FDH-catalyzed CO2 reduction reaction.

[0091] 1 H NMR tests confirmed the presence of substrates and products in the reaction solution, as shown in Figure 5 g. Add NAD into the reaction system + After that, NAD + The chemical shift of hydrogen atoms in the pyridine ring shifted from 9.17 ppm to 9.21 ppm, which was caused by the solvation effect. The signals of 1,6-NADH and 1,4-NADH were located at 6.96 ppm and 6.79 ppm, respectively. 20 PBC-Rh 3.5 Catalytic NAD + The signal was significantly reduced, indicating that NAD + The conversion rate is higher. Obviously, after the reaction, PBC, MX 20 PBC and PBC-Rh 3.5 Both 1,6-NADH and 1,4-NADH can be detected in MX 20 PBC-Rh 3.5 In the catalytic reaction solution, 1,6-NADH is almost undetectable, proving that the optimal catalyst MX 20 PBC-Rh 3.5 High selectivity for 1,4-NADH.

[0092] The TOF value of 1,4-NADH was calculated based on the NADH regeneration reaction within 1.5 hours to evaluate the performance of the photocatalyst. Figure 5 h shows that whether it is PBC or MX 20 For PBC, the order of 1,4-NADH TOF values is anchored [Cp*Rh] > homogeneous [Cp*Rh] > no [Cp*Rh]. 20 PBC-Rh 3.5 High NADH regeneration performance and excellent 1,4-NADH selectivity, the TOF value of 1,4-NADH reaches 1.16h -1 , compared with the TOF value of pure PBC (0.13h -1 ) is 8.9 times higher, MX 20 PBC-Rh 3.5 The stability of Figure 5 As shown in i, it can be recycled more than five times, and the recovery activity is basically consistent with the change of its actual Rh mass fraction. After three cycles, MX 20 PBC-Rh 3.5 The NADH regeneration activity decreased slightly and then gradually stabilized in the subsequent cycles, showing excellent stability.

[0093] 2. Photoregeneration of NADH coupled with enzyme FDH to reduce CO2 to generate formic acid; the test steps are as follows:

[0094] A 300W xenon lamp equipped with an ultraviolet cutoff filter (λ>420nm) was used as the light source. 30mL of phosphate buffer solution (pH=7) containing photocatalyst (1mg mL -1 ), NAD + (5mmol L -1 )、TEOA (1mmol L -1 ) and FDH (1U), the reactor was connected to a fully automatic online trace gas analysis system (Labsolar-6A, Beijing Perfect Technology Co., Ltd.), incubated in the dark under vacuum conditions for half an hour, and CO2 atmosphere was injected into the reactor and maintained at about 85kPa. Then, the xenon lamp was turned on with an irradiation distance of 15.0cm. Samples were taken every hour to monitor the yield of formic acid. After the reaction was completed, 100μL of the reaction sample was taken and sodium bicarbonate (5mmol L -1), Solution A (0.2 mL), Solution B (0.01 mL), and acetic anhydride solution (0.7 mL). Incubate at 50°C for 0.5 h, mix rapidly, wait 5 min, and measure absorbance at 515 nm using a UV-visible absorbance analyzer. Solution A consists of 0.5 g citric acid and 10 g acetamide dissolved in 100 mL of isopropanol. Solution B consists of 30 g sodium acetate dissolved in 100 mL of water.

[0095] The results are as follows Figure 6 As shown in Figure 2, the photocatalytically regenerated NADH is coupled with FDH to achieve the reduction of CO2 to formate. Figure 6 As shown in a, the yield of formate increases with the increase of reaction time, and the reaction rate tends to be stable after 4 hours. In the absence of [Cp*Rh], the formate yield of pure PBC is only 56.9 μmol. After loading MXene, 20 The formate yield of PBC increased by 2.2 times to 182.9 μmol. In the presence of homogeneous [Cp*Rh] 20 The formate production of PBC increased to 217.1 μmol and 295.4 μmol, respectively. 3.5 and MX 20 PBC-Rh 3.5 The formate yields of the photocatalysts further increased to 250.5 μmol and 313.1 μmol, respectively. This indicates that the introduction of MXene and anchoring of [Cp*Rh] play an important role in improving the catalytic performance of the photoenzyme. Figure 6 As shown in b, the CO2 reduction activity is consistent with the NADH reproduction rate and 1,4-NADH selectivity, demonstrating the key role of 1,4-NADH regeneration in stimulating the FDH catalytic reaction. Specifically, in the absence of [Cp*Rh], MX 20 The formate productivity of PBC reached 1219 μmol g -1 h -1 , is pure PBC (379μmolg -1 h -1 The TOF of CO2 reduction to formic acid was calculated to evaluate the conversion efficiency of the light-enzyme cascade catalytic reaction. After coupling with FDH enzyme, MX 20 PBC-Rh 3.5 The TOF reaches 0.74h -1 ( Figure 6 c), about pure PBC (0.13h -1 ) 6 times. MX 20 PBC-Rh 3.5It exhibits excellent 1,4-NADH regeneration performance, further promoting the reduction of CO2 to formate.

[0096] Based on the above research results, Figure 6 d The catalytic mechanism of the photoenzyme cascade reaction was elucidated. Under visible light irradiation, MX 20 PBC-Rh 3.5 There are two electron transfer pathways on the catalyst. Some of the photogenerated electrons excited on the PBC COF are transferred to the Ti3C2T3 with excellent conductivity. x and participate in NAD + Reduction to NADH and subsequent enzyme-catalyzed CO2 reduction (path I, green line). At the same time, other photogenerated electrons are transferred to [Cp*Rh] on bipyridine and then shuttled to NAD through the cycle of [Cp*Rh]. + The coenzyme 1,4-NADH is formed, and the coenzyme assists FDH to achieve CO2 reduction (path II, red line). In the absence of [Cp*Rh], only path I can be used to transfer photogenerated electrons. x It has excellent electrical conductivity and can still produce a certain amount of formate. NAD driven by photocatalyst + It is sustainably reduced to active 1,4-NADH, which is coupled with FDH to establish a light-enzyme cascade catalytic system, promoting the reduction of carbon dioxide to formate.

[0097] The above is a detailed description of the embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the scope of the present invention.

Claims

1. A photocatalyst, characterized in that It includes an amino-modified MXene, a COFs material and a rhodium atom catalyst; the amino-modified MXene and the COFs material are connected by a covalent bond; the rhodium atom in the rhodium atom catalyst and the COFs material are connected by an N-Rh bond.

2. The photocatalyst according to claim 1, characterized in that Calculated based on the total mass of the photocatalyst, the rhodium atoms account for 0.1 wt.% to 1 wt.% of the total mass of the photocatalyst.

3. The photocatalyst according to claim 1 or 2, characterized in that Calculated based on the total mass of the amino-modified MXene and the COFs material, the content of the amino-modified MXene is 10 wt.% to 25 wt.%.

4. The photocatalyst according to claim 1 or 2, characterized in that The aminated MXene includes aminated Ti3C2T x .

5. The photocatalyst according to claim 1 or 2, characterized in that The COFs material includes at least one of porphyrin-based COFs, bipyridyl-based COFs, iminopyridine COFs or triazine COFs.

6. The photocatalyst according to claim 1 or 2, characterized in that The rhodium atom catalyst includes at least one of a rhodium complex (Cp*RhCl2)2, rhodium nanoparticles, Rh2O3, and RhCl3.

7. A method for preparing the photocatalyst according to any one of claims 1 to 6, characterized in that: The steps include: S1. Mixing monomers for preparing COFs materials, amino-modified MXene materials, catalysts, and solvent I by ultrasonication; degassing by freezing-evacuating-thawing cycles of liquid nitrogen for several times, and then heating and reacting under vacuum conditions to obtain intermediate I; S2, mixing the intermediate I, the rhodium atom catalyst and the solvent II, stirring and reacting to obtain the product.

8. The preparation method according to claim 7, characterized in that The amino MXene material is prepared by the following method: The MXene material, 3-aminopropyltriethoxysilane and solvent III are mixed and stirred to obtain the amino-modified MXene material.

9. Use of the photocatalyst according to any one of claims 1 to 6 in NADH regeneration.

10. Use of the photocatalyst according to any one of claims 1 to 6 in catalytic reduction of formic acid with carbon dioxide.

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