Neighbor heteronuclear diatomic catalyst as well as preparation method and application thereof

Abstract

The invention provides a neighbor heteronuclear diatomic catalyst as well as a preparation method and application thereof. A porous covalent organic framework (COFs) is used as a platform, and an M1Y1-COF precursor with a clear structure is accurately constructed by using a metal coordination modification strategy; by creating a discrete atmosphere dynamic activation strategy, a precursor is driven to dynamically evolve in a mild environment, and the neighbor heteronuclear diatom M1Y1-COF-A catalyst is obtained. The active metals M and Y of the catalyst are in an atomic-scale dispersed and coordinated unsaturated state, and the atomic distances of M and Y are close under the structural confinement action of COF, so that strong electron interaction between M and Y is initiated, and an electron-enriched and stable M1-Y1 diatomic active center is formed after delocalization. The preparation conditions are mild, the process is simple and convenient, and the problems of fuzzy structure of a nanoparticle catalyst and poor linear proportion of adsorption energy of a reaction intermediate on a monatomic catalyst are solved. The catalyst is used in a selective hydrogenation reaction process, shows excellent hydrogenation activity and selectivity, and is easy to recover and reuse.

Description

Technical Field

[0001] The present invention belongs to the field of petrochemical industry, and particularly relates to a near-neighbor heteronuclear dual-atom catalyst, a preparation method thereof and an application thereof. The catalyst is mainly used in the process of selective hydrogenation reaction. Background Art

[0002] There is a problem that the active centers of nanoparticle catalysts have ambiguous structures, which greatly hinders the establishment of the correlation between structure and performance in heterogeneous catalytic hydrogenation systems. In this context, single-atom catalysts (SACs) with well-defined structures have become a promising option due to their precisely tunable electronic properties and geometric configurations. SACs can effectively reduce the adsorption degree of reaction intermediates and thus exhibit excellent selectivity. Unfortunately, the relatively slow dissociation of hydrogen on single atoms leads to an unsatisfactory linear proportional relationship among the adsorption energies of reaction intermediates, resulting in poor catalytic performance. Synergistic catalysis provides a solution to the above problems by simultaneously activating reactants to improve catalytic performance. However, the customization of heteronuclear, atomically dispersed dual active centers has rarely been reported.

[0003] Porous covalent organic frameworks (COFs) have attracted much attention in the field of materials research due to their well-defined structures and highly uniform pores. In particular, metal-containing covalent organic frameworks prepared by post-synthetic modification through direct integration of metal coordination modules show application potential in mild reactions such as photocatalysis and electrocatalysis. However, in the process of thermal catalysis, COFs are often used as precursors to pyrolyze at high temperatures (>700 °C) to form atomically dispersed catalysts, accompanied by the collapse of the COF structure and the loss of advantages such as uniform coordination.

[0004] Based on this, the present invention uses a coordination template strategy to precisely construct a dual-atom M1Y1-COF precursor by modifying crystalline covalent organic frameworks with the guiding effect of metal coordination; at the same time, a discrete atmosphere dynamic activation strategy is innovatively proposed to activate the precursor, thereby obtaining the M1Y1-COF-A catalyst. Due to the stable retention of the COF structure and the atmosphere-induced effect, the heteronuclear active metal M and Y atoms exhibit characteristics of discontinuity, low coordination, controllable spacing, and enhanced electronic interaction, promoting the simultaneous enhancement of selective hydrogenation activity, selectivity, and stability. Summary of the Invention

[0005] The object of the present invention is to provide a near-neighbor heteronuclear dual-atom catalyst, a preparation method thereof and an application thereof.

[0006] The near-neighbor heteronuclear dual-atom catalyst provided by the present invention is denoted as M1Y1-COF-A, where M is an active metal, which is one of Ni, Pd, Pt, Rh, Ru, and preferably Pd or Ni; the mass fraction of the active metal M in the catalyst is 0.01-5.00 wt.%, and preferably 0.05-4.00 wt.%; Y represents a promoter metal, which is one of Cu, Fe, Co, Zn, Ga, Sn, Mn, and preferably one of Cu, Fe, Co, Zn; the mass fraction of Y in the catalyst is 3.00-20.00 wt.%, and preferably 8.00-17.00 wt.%. A represents activation, and COF represents covalent organic framework, indicating that the catalyst maintains the COF framework structure after atmosphere treatment. The structural characteristics of this catalyst are as follows: the crystalline covalent organic framework structure modified by the heteronuclear metals M and Y is clear and stable, in which the active metals M and Y are atomically dispersed, without obvious agglomeration, and coordinatively unsaturated; at the same time, under the confinement of the COF structure, the atomic spacing between M and Y is controllable in the near-neighbor range, resulting in a strong electronic interaction between the two, and after delocalization, an electron-rich heteronuclear M1-Y1 dual-atom active center is formed.

[0007] The preparation method of the above-mentioned near-neighbor heteronuclear dual-atom catalyst provided by the present invention is characterized by being prepared according to the following specific steps:

[0008] A. Add Y3(PyCA)3·H2O and 4,4',4”-nitrilotribenzohydrazide (NTB-NH2) to a mixed solvent of mesitylene, dioxane, and trifluoroacetic acid with a volume ratio of 1 / 1 / 1-5 and ultrasonicate. The concentration of the Y salt is 0.031-0.045 mol / L, and the molar ratio of Y to NTB-NH2 is 1 / 1-5. After condensation reaction at 25-120 °C for 48-72 h, dry to obtain a single-metal Y-COF with a loading of 3.00-20.00 wt.%. According to the loading of the active metal M of 0.01-5.00 wt.%, add M and Y-COF to an organic solvent, and react at 25-80 °C for 8-16 h under an inert atmosphere, and dry at 25-80 °C to obtain a dual-atom M1Y1-COF precursor;

[0009] B. Place the above M1Y1-COF in a fixed-bed reactor, and introduce an inert atmosphere with a flow rate of 10-50 mL / min in a discrete feeding manner. Heat it to 100-150 °C at a rate of 1-600 °C / min to remove the impurity gases adsorbed on the surface of the precursor. Subsequently, keep the feeding method unchanged, switch to an activation atmosphere with a flow rate of 5-100 mL / min, and heat it to 150-250 °C at a rate of 1-600 °C / min to activate the precursor for 1-360 min to obtain an M1Y1-COF-A catalyst with discontinuous, low-coordination, controllable spacing, enhanced electronic interaction, and stable structure of the heteronuclear active metals M and Y atoms;

[0010] The described Y3(PyCA)3·H2O is a metal Y ion-containing complex, where Y represents one of Cu, Fe, Co, Zn, Ga, Sn, and Mn, and PyCA is 2-4-formaldehyde-pyrazolylamino; the described M salt is one of Ni(OAc)2·4H2O, Pd(OAc)2, H2PtCl4, Rh(NO3)3, and Ru(NO3)3.

[0011] The described discrete feeding method is one of intermittent pulse type, stepwise type, bubbling type, and spraying type.

[0012] The described activation atmosphere is one or two of NH3, CO, 10 vol.% H2 / N2 mixture gas, CH4, and C2H2.

[0013] Figure 1 XRD of the Ni1Cu1-COF precursor prepared at 200 °C in Example 1, the adjacent heteronuclear dual-atom Ni1Cu1-COF-A catalyst, and the NiCu-COF-A catalyst prepared at 300 °C in Comparative Example 1. It can be observed from the figure that the Ni1Cu1-COF-A catalyst and the precursor have completely similar diffraction peaks, indicating that the ordered crystal structure of the heteronuclear metal-organic framework is stably maintained during the atmosphere treatment process; while NiCu-COF-A-300 does not show diffraction peaks similar to the precursor, indicating that the atmosphere treatment at this temperature destroys the crystal structure related to COF.

[0014] Figure 2 IR spectra of the Ni1Cu1-COF precursor and the adjacent heteronuclear dual-atom Ni1Cu1-COF-A catalyst prepared in Example 1. It can be observed from the figure that both the precursor and the catalyst show all characteristic peaks of the hydrazone-linked framework, mainly including C=O, C=N, and C=C vibrations, indicating that the chemical bonds of COF do not break and recombine during the activation process.

[0015] Figure 3 STEM and Mapping photos of the heteronuclear dual-atom Ni1Cu1-COF-A catalyst prepared in Example 1. No obvious particles are observed from the figure, and Ni and Cu atoms are distributed at the atomic level in the organic framework structure and the two atoms are adjacent.

[0016] Figure 4 EXAFS spectra of the Ni1Cu1-COF precursor and the adjacent heteronuclear dual-atom Ni1Cu1-COF-A catalyst prepared in Example 1. Only the main peak at is observed from the figure, while there is no Ni-Ni coordination at , indicating that Ni species are dispersed in the form of single atoms; using intermittent pulse hydrogen activation, The peak intensity decreases significantly, which is attributed to the decrease in Ni-O coordination number and the shortening of Ni-N / O bond length. Similarly, there is no Cu-Cu coordination, and the Cu-O coordination signal disappears after activation. The Cu atom is only coordinated with two N atoms, and the Cu-N bond is shortened.

[0017] Figure 5 Ni 2p and Cu 2p XPS spectra of the Ni1Cu1-COF precursor prepared in Example 1 and the neighboring heteronuclear dual-atom Ni1Cu1-COF-A catalyst. It can be seen that after the intermittent pulse atmosphere treatment, the Ni δ+ species shift towards lower binding energy by 0.6 eV, indicating that activation enriches the electrons of the active metal. At the same time, Cu 2+ is easily transformed into Cu + species, and the increased electrons are filled into the pyridyl imine linking group (-Py-CH=N-) and trigger the electron delocalization between Ni and Cu.

[0018] Figure 6 Conversion and selectivity of the heteronuclear dual-atom Ni1Cu1-COF-A catalyst prepared in Example 1 in the acetylene selective hydrogenation reaction. The ethylene selectivity of this catalyst is as high as 90.7% under the condition of complete acetylene conversion.

[0019] Figure 7 Stability of the heteronuclear dual-atom Ni1Cu1-COF-A catalyst prepared in Example 1 in the acetylene selective hydrogenation reaction. During the long-term test of up to 210 h, the activity and selectivity hardly change.

[0020] Figure 8 Conversion and selectivity of the heteronuclear dual-atom Ni1Cu1-COF-A catalyst prepared in Example 2 in the acetylene selective hydrogenation reaction. The ethylene selectivity of this catalyst is as high as 92.0% under the condition of 95.5% acetylene conversion.

[0021] Figure 9 Conversion and selectivity of the heteronuclear dual-atom Ni1Cu1-COF-A catalyst prepared in Example 3 in the acetylene selective hydrogenation reaction. The ethylene selectivity of this catalyst is as high as 91.1% under the condition of 90.0% acetylene conversion.

[0022] Figure 10 Conversion and selectivity of the heteronuclear dual-atom Ni1Co1-COF-A catalyst prepared in Example 4 in the acetylene selective hydrogenation reaction. The ethylene selectivity of this catalyst is as high as 88.4% under the condition of 99.6% acetylene conversion.

[0023] Figure 11The conversion rate and selectivity of the heteronuclear diatomic Pd1Cu1-COF-A catalyst prepared in Example 5 in the acetylene selective hydrogenation reaction. The ethylene selectivity of this catalyst is as high as 87.2% under 99.1% conversion of acetylene.

[0024] Figure 12 The conversion rate and selectivity of the heteronuclear diatomic Ni1Cu1-COF-A catalyst prepared in Example 6 in the acetylene selective hydrogenation reaction. The ethylene selectivity of this catalyst is as high as 90.5% under 93.7% conversion of acetylene.

[0025] Figure 13 The conversion rate and selectivity of the heteronuclear bimetallic NiCu-COF-A catalyst prepared in Comparative Example 1 in the acetylene selective hydrogenation reaction. The ethylene selectivity of this catalyst is only 55.4% under 92.7% conversion of acetylene.

[0026] Advantages of the present invention:

[0027] Using porous covalent organic frameworks (COFs) as an innovative platform, a heteronuclear diatomic M1Y1-COF precursor is precisely constructed by means of metal coordination modification strategy; through the creation of a discrete atmosphere dynamic activation strategy, the dynamic evolution of the precursor in a mild environment is driven, thereby obtaining a near-neighbor heteronuclear diatomic M1Y1-COF-A catalyst. The active metals M and Y of this catalyst are atomically dispersed and coordinatively unsaturated. Under the structural confinement of COF, the distances between M and Y atoms are close, thus triggering a strong electronic interaction between the two, and forming an electron-rich and stable M1-Y1 diatomic active center after delocalization. The preparation conditions of the near-neighbor heteronuclear diatomic catalyst are mild, and the preparation process is simple, solving the problems of the blurred structure of traditional nanoparticle catalysts and the poor linear proportionality of the adsorption energies of reaction intermediates on single-atom catalysts. This catalyst can be used in the process of selective hydrogenation reaction, showing excellent hydrogenation activity and selectivity, outstanding catalytic performance, and being easy to recycle and reuse. Description of the drawings

[0028] Figure 1 XRD patterns of the Ni1Cu1-COF precursor prepared in Example 1 at 200 °C, the near-neighbor heteronuclear diatomic Ni1Cu1-COF-A catalyst, and the NiCu-COF-A catalyst prepared in Comparative Example 1 at 300 °C.

[0029] Figure 2 IR spectra of the Ni1Cu1-COF precursor and the near-neighbor heteronuclear diatomic Ni1Cu1-COF-A catalyst prepared in Example 1.

[0030] Figure 3 STEM and Mapping photos of the heteronuclear diatomic Ni1Cu1-COF-A catalyst prepared in Example 1.

[0031] Figure 4 EXAFS spectra and fitting results of the Ni1Cu1-COF precursor and the near-neighbor heteronuclear dual-atom Ni1Cu1-COF-A catalyst prepared in Example 1.

[0032] Figure 5 Ni 2p and Cu 2p XPS spectra of the Ni1Cu1-COF precursor and the near-neighbor heteronuclear dual-atom Ni1Cu1-COF-A catalyst prepared in Example 1.

[0033] Figure 6 Conversion and selectivity of the heteronuclear dual-atom Ni1Cu1-COF-A catalyst prepared in Example 1 in the acetylene selective hydrogenation reaction.

[0034] Figure 7 Stability of the heteronuclear dual-atom Ni1Cu1-COF-A catalyst prepared in Example 1 in the acetylene selective hydrogenation reaction.

[0035] Figure 8 Conversion and selectivity of the heteronuclear dual-atom Ni1Cu1-COF-A catalyst prepared in Example 2 in the acetylene selective hydrogenation reaction.

[0036] Figure 9 Conversion and selectivity of the heteronuclear dual-atom Ni1Cu1-COF-A catalyst prepared in Example 3 in the acetylene selective hydrogenation reaction.

[0037] Figure 10 Conversion and selectivity of the heteronuclear dual-atom Ni1Co1-COF-A catalyst prepared in Example 4 in the acetylene selective hydrogenation reaction.

[0038] Figure 11 Conversion and selectivity of the heteronuclear dual-atom Pd1Cu1-COF-A catalyst prepared in Example 5 in the acetylene selective hydrogenation reaction.

[0039] Figure 12 Conversion and selectivity of the heteronuclear dual-atom Ni1Cu1-COF-A catalyst prepared in Example 6 in the acetylene selective hydrogenation reaction.

[0040] Figure 13 Conversion and selectivity of the heteronuclear bimetallic NiCu-COF-A catalyst prepared in Comparative Example 1 in the acetylene selective hydrogenation reaction. Detailed implementation manners

[0041] Example 1

[0042] A. Cu3(PyCA)3·H2O and 4,4',4”-nitrilotribenzohydrazide (NTB-NH2) were added to a mixed solvent of mesitylene, dioxane, and trifluoroacetic acid with a volume ratio of 1 / 1 / 1.2 and ultrasonicated. The concentration of Cu 2+ was 0.045 mol / L, and the molar ratio of Cu to NTB-NH2 was 1 / 3. After condensation reaction at 120 °C for 72 h and drying, a single-metal Cu-COF with a loading of 16.5 wt.% was obtained; according to the active metal Ni loading of 4.00 wt.%, Ni(OAc)2·4H2O and Cu-COF were added to absolute ethanol, and the reaction was carried out at 60 °C for 12 h under nitrogen, and then dried at 60 °C to obtain a dual-atom Ni1Cu1-COF precursor;

[0043] B. The above Ni1Cu1-COF was placed in a fixed-bed reactor, and nitrogen with a flow rate of 50 mL / min was introduced in an intermittent pulse feeding mode. It was heated to 120 °C at a rate of 10 °C / min to remove the impurity gases adsorbed on the surface of the precursor. Subsequently, while keeping the feeding mode unchanged, a 10 vol.% H2 / N2 mixed gas with a flow rate of 100 mL / min was switched, and it was heated to 200 °C at a rate of 10 °C / min to activate the precursor for 240 min, obtaining a Ni1Cu1-COF-A catalyst with heteronuclear active metals Ni and Cu atoms being discontinuous, low-coordinated, controllable spacing, enhanced electronic interaction, and stable structure.

[0044] The catalyst prepared above was used for the acetylene selective hydrogenation reaction experiment:

[0045] 0.18 g of the above catalyst and 0.72 g of quartz sand were weighed and loaded into a fixed-bed reactor. A mixed gas with a volume ratio of H2 / C2H2 / C2H4 = 30 / 1 / 99, with N2 as the balance gas (67.5 vol.%) and a total flow rate of 120 mL / min, was introduced and tested in the range of 80 - 200 °C. The gas at the reactor outlet was detected by a gas chromatograph. The results are shown in Figure 6 , and the ethylene selectivity of this catalyst can reach 90.7% under the condition of complete conversion of acetylene.

[0046] Example 2

[0047] A. Cu3(PyCA)3·H2O and 4,4',4”-nitrilotribenzohydrazide (NTB-NH2) were added to a mixed solvent of mesitylene, dioxane, and trifluoroacetic acid with a volume ratio of 1 / 1 / 1.2 and ultrasonicated. The concentration of Cu 2+With a concentration of 0.045 mol / L and a molar ratio of Cu to NTB-NH2 of 1 / 3, after condensation reaction at 120 °C for 72 h and drying, a single-metal Cu-COF with a loading of 16.5 wt.% was obtained; according to the loading of active metal Ni being 4.00 wt.%, Ni(OAc)2·4H2O and Cu-COF were added to absolute ethanol, and reacted at 60 °C for 12 h under nitrogen, and dried at 60 °C to obtain a dual-atom Ni1Cu1-COF precursor;

[0048] B. The above Ni1Cu1-COF was placed in a fixed-bed reactor, and nitrogen with a flow rate of 50 mL / min was introduced in a spray feeding mode, heated to 120 °C at a rate of 10 °C / min to remove the impurity gases adsorbed on the surface of the precursor, then keeping the feeding mode unchanged, switching to a 10 vol.% H2 / N2 mixed gas with a flow rate of 100 mL / min, and heating to 200 °C at a rate of 10 °C / min to activate the precursor for 240 min, obtaining a Ni1Cu1-COF-A catalyst with heteronuclear active metals Ni and Cu atoms being discontinuous, low-coordinated, controllable in spacing, enhanced in electronic interaction and stable in structure.

[0049] Example 3

[0050] A. Cu3(PyCA)3·H2O and 4,4',4”-nitrilotribenzohydrazide (NTB-NH2) were added to a mixed solvent of mesitylene, dioxane, and trifluoroacetic acid with a volume ratio of 1 / 1 / 1.2 and ultrasonicated, Cu 2+ With a concentration of 0.045 mol / L and a molar ratio of Cu to NTB-NH2 of 1 / 3, after condensation reaction at 120 °C for 72 h and drying, a single-metal Cu-COF with a loading of 16.5 wt.% was obtained; according to the loading of active metal Ni being 4.00 wt.%, Ni(OAc)2·4H2O and Cu-COF were added to absolute ethanol, and reacted at 60 °C for 12 h under nitrogen, and dried at 60 °C to obtain a dual-atom Ni1Cu1-COF precursor;

[0051] B. The above Ni1Cu1-COF was placed in a fixed-bed reactor, and nitrogen with a flow rate of 50 mL / min was introduced in an intermittent pulse feeding mode, heated to 120 °C at a rate of 10 °C / min to remove the impurity gases adsorbed on the surface of the precursor, then keeping the feeding mode unchanged, switching to CO with a flow rate of 100 mL / min, and heating to 200 °C at a rate of 10 °C / min to activate the precursor for 240 min, obtaining a Ni1Cu1-COF-A catalyst with heteronuclear active metals Ni and Cu atoms being discontinuous, low-coordinated, controllable in spacing, enhanced in electronic interaction and stable in structure.

[0052] Example 4

[0053] A. Co3(PyCA)3·H2O and 4,4',4”-nitrilotribenzohydrazide (NTB-NH2) were added to a mixed solvent of mesitylene, dioxane, and trifluoroacetic acid with a volume ratio of 1 / 1 / 1.2 and sonicated. The concentration of Co 2+ was 0.045 mol / L, and the molar ratio of Co to NTB-NH2 was 1 / 3. After condensation reaction at 120 °C for 72 h, it was dried to obtain a single-metal Co-COF with a loading of 16.5 wt.%. According to the loading of active metal Ni being 4.00 wt.%, Ni(OAc)2·4H2O and Co-COF were added to absolute ethanol, and the reaction was carried out at 60 °C for 12 h under nitrogen, and then dried at 60 °C to obtain a dual-atom Ni1Co1-COF precursor;

[0054] B. The above Ni1Co1-COF was placed in a fixed-bed reactor, and nitrogen with a flow rate of 50 mL / min was introduced in an intermittent pulse feeding mode. It was heated to 120 °C at a rate of 10 °C / min to remove the impurity gases adsorbed on the surface of the precursor. Subsequently, while keeping the feeding mode unchanged, a 10 vol.% H2 / N2 mixed gas with a flow rate of 100 mL / min was switched, and it was heated to 200 °C at a rate of 10 °C / min to activate the precursor for 240 min, obtaining a Ni1Co1-COF-A catalyst with heteronuclear active metals Ni and Co atoms being discontinuous, low-coordinated, controllable in spacing, enhanced in electronic interaction, and stable in structure.

[0055] Example 5

[0056] A. Cu3(PyCA)3·H2O and 4,4',4”-nitrilotribenzohydrazide (NTB-NH2) were added to a mixed solvent of mesitylene, dioxane, and trifluoroacetic acid with a volume ratio of 1 / 1 / 1.2 and sonicated. The concentration of Cu 2+ was 0.045 mol / L, and the molar ratio of Cu to NTB-NH2 was 1 / 3. After condensation reaction at 120 °C for 72 h, it was dried to obtain a single-metal Cu-COF with a loading of 16.5 wt.%. According to the loading of active metal Pd being 0.6 wt.%, Pd(OAc)2 and Cu-COF were added to absolute ethanol, and the reaction was carried out at 60 °C for 12 h under nitrogen, and then dried at 60 °C to obtain a dual-atom Pd1Cu1-COF precursor;

[0057] B. Place the above Pd1Cu1-COF in a fixed-bed reactor, introduce nitrogen with a flow rate of 50 mL / min in an intermittent pulse feeding mode, heat it to 120 °C at a rate of 10 °C / min to remove the impurity gases adsorbed on the surface of the precursor, then keep the feeding mode unchanged, switch to a 10 vol.% H2 / N2 mixed gas with a flow rate of 100 mL / min, and heat it to 200 °C at a rate of 10 °C / min to activate the precursor for 240 min, obtaining a Pd1Cu1-COF-A catalyst with discontinuous, low-coordination, controllable spacing, enhanced electronic interaction and stable structure of heteronuclear active metal Pd and Cu atoms.

[0058] Example 6

[0059] A. Add Cu3(PyCA)3·H2O and 4,4',4”-nitrilotribenzohydrazide (NTB-NH2) to a mixed solvent of mesitylene, dioxane, and trifluoroacetic acid with a volume ratio of 1 / 1 / 1.2 and ultrasonicate. The concentration of Cu 2+ is 0.045 mol / L, and the molar ratio of Cu to NTB-NH2 is 1 / 3. After condensation reaction at 120 °C for 72 h, dry it to obtain a single-metal Cu-COF with a loading of 16.5 wt.%. According to the loading of active metal Ni being 4.00 wt.%, add Ni(OAc)2·4H2O and Cu-COF to absolute ethanol, react at 60 °C for 12 h under nitrogen, and dry at 60 °C to obtain a dual-atom Ni1Cu1-COF precursor;

[0060] B. Place the above Ni1Cu1-COF in a fixed-bed reactor, introduce nitrogen with a flow rate of 50 mL / min in an intermittent pulse feeding mode, heat it to 120 °C at a rate of 600 °C / min to remove the impurity gases adsorbed on the surface of the precursor, then keep the feeding mode unchanged, switch to a 10 vol.% H2 / N2 mixed gas with a flow rate of 100 mL / min, and heat it to 200 °C at a rate of 600 °C / min to activate the precursor for 1 min, obtaining a Ni1Cu1-COF-A catalyst with discontinuous, low-coordination, controllable spacing, enhanced electronic interaction and stable structure of heteronuclear active metal Ni and Cu atoms.

[0061] Comparative Example 1

[0062] A. Add Cu3(PyCA)3·H2O and 4,4',4”-nitrilotribenzohydrazide (NTB-NH2) to a mixed solvent of mesitylene, dioxane, and trifluoroacetic acid with a volume ratio of 1 / 1 / 1.2 and ultrasonicate. The concentration of Cu 2+With a concentration of 0.045 mol / L and a molar ratio of Cu to NTB-NH2 of 1 / 3, after condensation reaction at 120 °C for 72 h and then drying, a single-metal Cu-COF with a loading of 16.5 wt.% was obtained; according to the loading of active metal Ni being 4.00 wt.%, Ni(OAc)2·4H2O and Cu-COF were added to absolute ethanol, and the reaction was carried out at 60 °C for 12 h under nitrogen, and then dried at 60 °C to obtain a dual-atom Ni1Cu1-COF precursor;

[0063] B. The above-mentioned Ni1Cu1-COF was placed in a fixed-bed reactor, and nitrogen with a flow rate of 50 mL / min was introduced in an intermittent pulse feeding mode, heated to 120 °C at a rate of 10 °C / min to remove the impurity gases adsorbed on the surface of the precursor, then keeping the feeding mode unchanged, switching to a 10 vol.% H2 / N2 mixed gas with a flow rate of 100 mL / min, and heating to 300 °C at a rate of 10 °C / min to activate the precursor for 240 min to obtain a heteronuclear dual-metal NiCu-COF-A catalyst.

Claims

1. A preparation method of a near-neighbor heteronuclear diatomic catalyst, characterized in that It is prepared according to the following specific steps: A. Add Y3(PyCA)3·H2O and 4,4',4”-nitrilotribenzoylhydrazide NTB-NH2 into a mixed solvent of mesitylene, dioxane, and trifluoroacetic acid with a volume ratio of 1 / 1 / 1 to 5, and ultrasonicate. Y is one of Cu, Fe, Co, Zn, Ga, Sn, and Mn; the concentration of the Y salt is 0.031 - 0.045 mol / L, and the molar ratio of Y to NTB-NH2 is 1 / 1 to 5. After condensation reaction at 25 - 120 °C for 48 - 72 h, dry to obtain a single-metal Y-COF with a loading of 3.00 - 20.00 wt.%. According to the loading of the active metal M of 0.01 - 5.00 wt.%, add M and Y-COF into an organic solvent, and react at 25 - 80 °C for 8 - 16 h under an inert atmosphere, and dry at 25 - 80 °C to obtain a dual-atom M1Y1-COF precursor; B. Place the above M1Y1-COF in a fixed-bed reactor, introduce an inert atmosphere with a flow rate of 10 - 50 mL / min, heat it at a rate of 1 - 600 °C / min to 100 - 150 °C to remove the impurity gases adsorbed on the surface of the precursor. Subsequently, keep the feeding method unchanged, switch to an activation atmosphere with a flow rate of 5 - 100 mL / min, and heat it at a rate of 1 - 600 °C / min to 150 - 250 °C to activate the precursor for 1 - 360 min to obtain the M1Y1-COF-A catalyst.

2. The preparation method of the adjacent heteronuclear dual-atom catalyst according to claim 1, wherein Y3(PyCA)3·H2O described in step A is a complex containing metal Y ions, and PyCA is 2-4-formaldehyde-pyrazolylamino.

3. The preparation method of the adjacent heteronuclear dual-atom catalyst according to claim 1, wherein the active metal M salt described in step A is one of Ni(OAc)2·4H2O, Pd(OAc)2, H2PtCl4, Rh(NO3)3, and Ru(NO3)3.

4. The preparation method of the adjacent heteronuclear dual-atom catalyst according to claim 1, wherein the feeding method described in step B is one of intermittent pulse type, stepwise type, bubbling type, and spraying type.

5. The preparation method of the adjacent heteronuclear dual-atom catalyst according to claim 1, wherein the activation atmosphere described in step B is one or two of NH3, CO, 10 vol.% H2 / N2 mixture gas, CH4, and C2H2.

6. A near-neighbor heteronuclear diatomic catalyst prepared by the method according to claim 1, characterized in that This catalyst is denoted as M1Y1-COF-A, where M is the active metal, which is one of Ni, Pd, Pt, Rh, and Ru, and the mass fraction of the active metal M in the catalyst is 0.01 - 5.00 wt.%; Y represents the promoter metal, which is one of Cu, Fe, Co, Zn, Ga, Sn, and Mn, and the mass fraction of Y in the catalyst is 3.00 - 20.00 wt.%, and A represents activation; COF represents covalent organic framework.

7. Use of the near-neighbor heteronuclear diatomic catalyst according to claim 6 in the selective hydrogenation of unsaturated carbon-carbon bonds, characterized in that, Weigh 0.05 - 0.50 g of the above catalyst and 0.20 - 2.00 g of quartz sand and load them into a fixed-bed micro-reactor; introduce a mixed gas with a volume ratio of H2 / C2H2 / C2H4 = 5 / 1 / 99 - 30 / 1 / 99, N2 as the balance gas with a volume percentage of 30 vol.% - 67.5 vol.%, and a total flow rate of 45 - 120 mL / min, and conduct tests in the range of 80 - 200 °C. The gas at the reactor outlet is detected by a gas chromatograph.

8. Use of the near-neighbor heteronuclear diatomic catalyst according to claim 6 in the selective hydrogenation of unsaturated carbon-oxygen bonds, characterized in that, Weigh 25 - 50 mg of the above catalyst and 60 mL of a 2-ethylanthraquinone working solution with a concentration of 80 - 120 g / L and load them into a 100 mL reaction kettle; introduce hydrogen to 0.1 - 0.5 MPa, heat to 40 - 80 °C and then turn on the stirrer, and regularly open the liquid-phase valve to take 1 mL of the working solution for analysis.

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