Heterogeneous photocatalyst containing fluorine boron pyrrole photosensitizer
阅读说明：本技术 一种含氟硼吡咯类光敏剂的多相光催化剂 (Heterogeneous photocatalyst containing fluorine boron pyrrole photosensitizer ) 是由 杨文博 陶胜洋 于 2021-07-21 设计创作，主要内容包括：本发明提供了一种含氟硼吡咯类光敏剂的多相光催化剂,所述催化剂以氟硼吡咯类光敏剂为活性位点,以丙烯酸酯聚合物为基体,所述活性位点以共价键形式连接于所述基体上；所述催化剂由聚合单体聚合而成,所述聚合单体包括含有丙烯酸酯基的氟硼吡咯及丙烯酸酯类化合物。本发明通过将氟硼吡咯类光敏剂以共价键形式束缚于丙烯酸酯聚合物基体上,一方面提高了多相催化剂的稳定性,另一方面减少了由于分子间碰撞而导致的能量损耗,使其催化性能更好的发挥。本发明构筑的多孔空心球型多相光催化剂,解决了由于光穿透性差而导致材料中心活性位点冗余的问题,极大提高了光能的利用率。将该多相光催化剂应用于光催化反应中,显著提高了催化效率。(The invention provides a heterogeneous photocatalyst containing a BODIPY photosensitizer, wherein the catalyst takes the BODIPY photosensitizer as an active site, takes an acrylate polymer as a matrix, and the active site is connected to the matrix in a covalent bond mode; the catalyst is formed by polymerizing a polymerization monomer, wherein the polymerization monomer comprises fluorine boron pyrrole containing an acrylate group and an acrylate compound. According to the invention, the BODIPY photosensitizer is bound on the acrylate polymer matrix in a covalent bond manner, so that on one hand, the stability of the heterogeneous catalyst is improved, and on the other hand, the energy loss caused by intermolecular collision is reduced, and the catalytic performance of the heterogeneous catalyst is better exerted. The porous hollow sphere type multiphase photocatalyst constructed by the invention solves the problem of redundant active sites in the center of the material caused by poor light penetrability, and greatly improves the utilization rate of light energy. The heterogeneous photocatalyst is applied to photocatalytic reaction, and the catalytic efficiency is obviously improved.)
1. The heterogeneous photocatalyst containing the BODIPY photosensitizer is characterized in that the catalyst takes the BODIPY photosensitizer as an active site, takes an acrylate polymer as a matrix, and the active site is connected to the matrix in a covalent bond mode; the catalyst is formed by polymerizing a polymerization monomer, wherein the polymerization monomer comprises fluorine boron pyrrole containing an acrylate group and an acrylate compound.
2. The heterogeneous photocatalyst according to claim 1, wherein the mass fraction of said fluoroborole containing acrylate groups in the catalyst is in the range of 0.0001 to 10 wt%, preferably 0.01 to 5 wt%, more preferably 0.03 to 0.28 wt%.
3. The heterogeneous photocatalyst according to claim 1, wherein said acrylate group-containing fluoroborole has a fluoroborole group and an acrylate group and has the following structural formulae:
4. the heterogeneous photocatalyst of claim 3, wherein the acrylate group is selected from the following structures:
the BODIPY group has the following structure:
wherein R is2、R3、R4、R5、R6、R7Independently selected from H, Cl, Br, I, (CH)2)b--R8b is 0-5 or a vinyl group of the following structure;
and R is2、R3、R4、R5、R6、R7Not H at the same time;
R8is selected from CH3Or the following structural group:
phenyl or phenyl containing methyl substituents:
phenyl group containing cyano substituent:
phenyl with amino substituents:
phenyl containing a hydroxyl substituent:
ether chain-containing phenyl group:
nitrogen heterocyclic substituent:
furan substituent:
thiophene substituent groups:
a naphthalene substituent:
an anthracene substituent:
pyrene substituent:
a carbazole substituent:
phenothiazine substituent:
biphenyl substituent:
diphenylmethyl substituents:
5. the heterogeneous photocatalyst according to claim 1, wherein in said acrylate group-containing fluoroborole, the mode of attachment of the fluoroborole group to the acrylate group is selected from the group consisting of: directly connected with each other, connected with each other by an alkyl chain, connected with a plurality of benzene rings, and sequentially or alternately connected by the benzene rings and the alkyl chains; preferably, the total number of carbon atoms on the alkyl chain of the connecting part is less than or equal to 10, the total number of benzene rings of the connecting part is less than or equal to 5, and the connection modes of the benzene rings are independently selected from ortho-position, meta-position and para-position.
6. The heterogeneous photocatalyst as set forth in claim 1, wherein the acrylate compound is one or more selected from the group consisting of dipropylene glycol diacrylate, glycidyl methacrylate, ethylene glycol dimethacrylate, ethoxylated trimethylolpropane triacrylate and trimethylolpropane triacrylate.
7. The heterogeneous photocatalyst of claim 1, wherein the catalyst is of a spherical structure; the spherical structure is selected from a hollow spherical structure and a solid spherical structure; the catalyst is selected from porous structures and non-porous structures.
8. A method for preparing the heterogeneous photocatalyst of any one of claims 1 to 7, comprising the steps of:
(1) preparing oil-in-water or water-in-oil-in-water type micro-droplets by using a micro-fluidic chip, wherein a water phase is a surfactant water solution, and an oil phase comprises a polymerization monomer and a photoinitiator;
(2) curing the micro-droplets by using ultraviolet light to obtain a spherical heterogeneous photocatalyst;
the micro-fluidic chip is selected from a coaxial flow type micro-fluidic chip and is used for preparing oil-in-water type single emulsion micro-droplets; or flow focusing type and double coaxial flow type micro-fluidic chips, which are used for preparing water-in-oil-in-water type double-emulsion micro-droplets.
9. Use of a heterogeneous photocatalyst according to any one of claims 1-7 in photocatalytic reactions.
10. Use according to claim 9, characterized in that the photocatalytic reaction is chosen from the reactions for the synthesis of juglone, aza-Henry, Alder-ene and the oxidation of thiols to disulfides.
Technical Field
The invention belongs to the field of functional composite materials, and particularly relates to a heterogeneous photocatalyst taking a BODIPY photosensitizer as an active site and an acrylate polymer as a matrix.
Background
Light energy is one of the most important energy sources on the earth, and the chemical reaction carried out by utilizing the light energy provides a more moderate and rapid special reaction path for the chemical conversion which needs to be carried out under complex conditions originally. Until now, homogeneous photocatalytic systems have been developed rapidly due to their good dispersion, uniform illumination and high reaction efficiency. However, homogeneous photocatalysis has a great disadvantage in that the catalysts, especially the commonly used noble metal catalysts, cannot be easily and quickly recovered and reused, which gradually brings the heterogeneous photocatalysis to the field of scientists.
However, there are some problems to be solved in heterogeneous photocatalysis, such as: the recycling frequency of the catalyst is still not high, and the problems of loss of catalytic sites or serious photobleaching exist; the catalyst is nano-particles or irregular powder, is difficult to separate, and needs to be further separated in a settling and filtering mode and recycled; the inside of the catalyst or the center of the reaction system is difficult to participate in the reaction because light is difficult to reach; the heterogeneous catalyst has no good homogeneous phase dispersion in solution and poor mass transfer effect, so that the reaction efficiency is often inferior to that of homogeneous catalysis.
In heterogeneous photocatalysis, the immobilization of the catalytically active site, i.e. the photosensitizer, on the substrate directly affects the performance and stability of the catalyst. Intermolecular force encapsulation, coating is a commonly used means of immobilizing the active site (Han, X.; Bourne, R.A.; Poliakoff, M.; George, M.W.Chem.Sci.2011, 2, 1059-laid 1067; Becker-Jahn, J.; Griebel, J.; Gla β, S.; Langwski, P.; Nie β, S.; Schulze, A.Catal.today 2021, 364, 256-laid 262; Huang, L.; Li, Z.; Zhao, Y.; Yang, J.; Yang, Y.; Pendharkar, A.I.; Zhang, Y.; Kelmar, S.; Chen, L.; Wu, W.; Zhao, J.; G.Adv.7, Mat 16089), and no such means are readily lost.
Therefore, the invention is of great importance for the catalyst which has good stability, adjustable load capacity and excellent catalytic effect under the condition of only loading a very small amount of catalyst.
Disclosure of Invention
In order to overcome the problems, the invention provides a heterogeneous photocatalyst containing a fluorine boron pyrrole photosensitizer.
The technical scheme of the invention is as follows:
in one aspect, the invention provides a heterogeneous photocatalyst containing a BODIPY photosensitizer, wherein the catalyst takes the BODIPY photosensitizer as an active site, takes an acrylate polymer as a matrix, and the active site is connected to the matrix in a covalent bond mode; the catalyst is formed by polymerizing a polymerization monomer, wherein the polymerization monomer comprises fluorine boron pyrrole containing an acrylate group and an acrylate compound.
Optionally, the catalyst morphology is hollow non-porous spheres, hollow porous spheres, solid non-porous spheres, or solid porous spheres.
The fluorine boron pyrrole containing acrylate group has: the structural formulas of the BODIPY group and the acrylate group are respectively as follows:
the acrylate group is selected from the following structures:
the BODIPY group has the following structure:
wherein R is2、R3、R4、R5、R6、R7Independently selected from H, Cl, Br, I, (CH)2)b-R8b is 0 to 5 or a vinyl group of the following structure,
and R is2、R3、R4、R5、R6、R7Not H at the same time;
R8is selected from CH3Or a structural group of the following formula,
phenyl or phenyl containing methyl substituents:
phenyl group containing cyano substituent:
phenyl with amino substituents:
phenyl containing a hydroxyl substituent:
ether chain-containing phenyl group:
nitrogen heterocyclic substituent:
furan substituent:
thiophene substituent groups:
a naphthalene substituent:
an anthracene substituent:
pyrene substituent:
a carbazole substituent:
phenothiazine substituent:
biphenyl substituent:
diphenylmethyl substituents:
in the fluorine boron pyrrole containing acrylate group, the connection mode of the fluorine boron pyrrole group and the acrylate group is selected from the following groups: directly connected with each other, connected with each other by an alkyl chain, connected with a plurality of benzene rings, and sequentially or alternately connected by the benzene rings and the alkyl chains. Preferably, the total number of carbon atoms on the alkyl chain of the connecting part is less than or equal to 10, the total number of benzene rings of the connecting part is less than or equal to 5, and the connection modes of the benzene rings are independently selected from ortho-position, meta-position and para-position.
Alternatively, the mass fraction of the acrylate group-containing fluoroboric pyrrole in the catalyst is in the range of 0.0001 to 10 wt%, preferably 0.01 to 5 wt%, more preferably 0.03 to 0.28 wt%.
The acrylate compound is optionally one or more selected from dipropylene glycol diacrylate, glycidyl methacrylate, ethylene glycol dimethacrylate, ethoxylated trimethylolpropane triacrylate and trimethylolpropane triacrylate.
In another aspect, the present invention provides a method for preparing a spherical heterogeneous photocatalyst, which uses a microfluidic chip to controllably prepare oil-in-water (O/W) or water-in-oil-in-water (W/O/W) type micro-droplets, wherein the aqueous phase is a surfactant aqueous solution, and the oil phase comprises a polymerization monomer and a photoinitiator; further, ultraviolet light is used for curing the micro-droplets to obtain the spherical heterogeneous photocatalyst.
The polymerization monomer comprises fluorine boron pyrrole containing acrylate group and acrylate compound. Dissolving the fluoboric pyrrole containing the acrylate group into an oil phase system containing the acrylate compound and the photoinitiator to form a precursor solution for preparing the catalyst. The mass fraction of the BODIPY compound in the precursor liquid is in the range of 0.0001 to 10 wt%, preferably 0.01 to 5 wt%, more preferably 0.03 to 0.28 wt%.
And (3) carrying out ultraviolet irradiation on the micro-droplets prepared by the micro-fluidic chip to cure the micro-droplets, wherein the curing time can be about 30s, and the curing time can be properly prolonged along with the increase of the addition amount of the BODIPY.
Optionally, the cured spherical heterogeneous photocatalyst can be washed with water and ethanol for multiple times, dried and collected.
Optionally, the microfluidic chip for controllable synthesis may be selected from (1) a coaxial flow type microfluidic chip for preparing oil-in-water (O/W) type single emulsion micro-droplets; (2) the flow focusing type and (3) the double coaxial flow type micro-fluidic chip are used for preparing water-in-oil-in-water (W/O/W) type double-emulsion micro-droplets.
Alternatively, the aqueous system used is an aqueous surfactant solution; the surfactant is selected from Tween-20, sodium dodecylbenzenesulfonate, sodium dodecylsulfate, poloxamer, polyvinyl alcohol, and fluorinated solution. Preference is given to polyvinyl alcohols whose Mw can be 13000-23000, -31000, -47000, -67000, -145000, -205000. Optionally, the surfactant is present in a mass fraction of 0.1 to 30 wt%, preferably 1 to 15 wt%, more preferably 3 to 8 wt%.
Optionally, the acrylate compound is selected from one or more of dipropylene glycol diacrylate, glycidyl methacrylate, ethylene glycol dimethacrylate, ethoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate; the photoinitiator is selected from 2-hydroxy-2-methyl propiophenone, 2-hydroxy-4' - (2-hydroxyethoxy) -2-methyl propiophenone, 2-dimethoxy-2-phenyl acetophenone, and 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone. Specifically, for example, glycidyl methacrylate and trimethylolpropane triacrylate are used as an acrylate compound in the polymerization monomers, and 2-hydroxy-2-methyl propiophenone is used as a photoinitiator.
Alternatively, a phase separation agent may be added to the oil phase according to actual needs to form a pore structure when the droplets are solidified. The phase separating agent is selected from undecanol, hexadecane, 2-methylpentane, cyclohexanol, dodecanol, dioctyl phthalate, diisodecyl phthalate, etc.
In yet another aspect, the present invention uses the above-described heterogeneous photocatalyst in a photocatalytic reaction.
Alternatively, the photocatalytic reaction includes a reaction for synthesizing juglone, an aza-Henry reaction, an Alder-ene reaction, and an oxidation reaction of thiol to disulfide.
Compared with the prior art, the invention has the following beneficial effects:
(1) the research of the invention finds that in the selection of the catalytic active sites, the boron-fluorine pyrrole compound has the characteristics of strong light absorption capacity, good light stability, high triplet state quantum yield and easy derivatization. According to the invention, the BODIPY compound with a specific structure is bound on the acrylate polymer matrix in a covalent bond mode to realize immobilization of the photosensitizer, so that on one hand, the stability of the heterogeneous catalyst is improved, and on the other hand, the energy loss caused by intermolecular collision is reduced, and the catalytic performance of the heterogeneous catalyst is better exerted.
(2) On the aspect of catalyst morphology design, the porous hollow sphere multiphase photocatalyst constructed by the invention is beneficial to the transfer of substances on one hand, and solves the problem of redundant active sites in the center of the material due to poor light penetrability on the other hand, thereby greatly improving the utilization rate of light energy.
(3) The heterogeneous catalyst is applied to the reaction of synthesizing juglone by flowing photocatalysis, the yield can be maintained for 30 hours without reduction, and the reaction rate can reach 10 times of that of homogeneous reaction in which the boron fluorine pyrrole with the same structure participates. The catalyst can also be applied to various reaction systems, such as aza-Henry reaction, Alder-ene reaction and oxidation reaction from mercaptan to disulfide, and the conversion rate is more than 95%.
Drawings
FIG. 1 is a schematic diagram of the preparation of single emulsion micro-droplets using a coaxial flow microfluidic chip;
FIG. 2 is a schematic diagram of the preparation of double emulsion micro-droplets using a flow focusing micro-fluidic chip;
FIG. 3 is a schematic diagram of the preparation of double emulsion micro-droplets using a dual coaxial flow microfluidic chip;
FIG. 4 is a microscope photograph of (a) micro-droplets containing 0.07 wt% of BODIPY and (b) a fluorescence microscope photograph of a spherical heterogeneous photocatalyst formed by UV curing;
FIG. 5 is a cross-sectional view of a heterogeneous photocatalyst containing 0.07 wt% of BODIPY, showing (a) a fluorescence confocal micrograph, (b) a fluorescence spectrum, and (c) a light intensity distribution;
FIG. 6 is a scanning electron microscope image of a heterogeneous photocatalyst with a pore structure and containing 0.07 wt% of BODIPY and a cross section of the heterogeneous photocatalyst under different scales;
FIG. 7 is a scanning electron microscope image of a spherical acrylate polymer matrix without BODIPY with a pore structure and a cross section thereof under different scales;
FIG. 8 is a graph of UV-visible absorption spectra of nonporous polymers formed after incorporation of varying proportions of BODIPY into acrylate compounds;
FIG. 9 is a scanning electron microscope image of a heterogeneous photocatalyst containing 0.07 wt% of BODIPY without a pore structure and a cross section thereof under different scales;
FIG. 10 shows (a) the stability of the loading and (b) the stability of the reaction for the continuous catalytic synthesis of juglone for heterogeneous photocatalysts containing 0.07 wt% of BODIPY.
Detailed Description
Fluoroboropyrroles
The used fluoboric pyrrole compound is a fluoboric pyrrole derivative with acrylate group. The purpose of derivatization of the BODIPY by the acrylate group is to connect the photosensitizer with the polymer matrix in a covalent bond mode, and compared with the connection mode through intermolecular force, ionic bond, encapsulation, coating and the like, the connection mode is more stable, the photosensitizer is not easy to lose, and the cycle stability of the heterogeneous catalyst is greatly improved. And the mass fraction of the boron-fluorine pyrrole in the catalyst is easy to adjust, rather than being single and uncontrollable, and the catalyst with a proper proportion can be prepared according to the actual needs of the reaction.
The fluorine boron pyrrole containing acrylate group has: the structural formulas of the BODIPY group and the acrylate group are respectively as follows:
the acrylate group is selected from the following structures:
the BODIPY group has the following structure:
wherein R is2、R3、R4、R5、R6、R7Independently selected from H, Cl, Br, I, (CH)2)b-R8b is 0 to 5 or a vinyl group of the following structure,
and R is2、R3、R4、R5、R6、R7When the reaction is not simultaneously H, the reaction solution is not H,
R8is selected from CH3Or a structural group of the following formula,
phenyl or phenyl containing methyl substituents:
phenyl group containing cyano substituent:
phenyl with amino substituents:
phenyl containing a hydroxyl substituent:
ether chain-containing phenyl group:
nitrogen heterocyclic substituent:
furan substituent:
thiophene substituent groups:
a naphthalene substituent:
an anthracene substituent:
pyrene substituent:
a carbazole substituent:
phenothiazine substituent:
biphenyl substituent:
diphenylmethyl substituents:
in the fluorine boron pyrrole containing acrylate group, the connection mode of the fluorine boron pyrrole group and the acrylate group is selected from the following groups:
directly connected, for example:
linked by an alkyl chain, for example:
linked in multiple benzene rings, for example:
the benzene ring and the alkyl chain are connected sequentially or alternately, for example:
preferably, the total number of carbon atoms on the alkyl chain of the connecting part is less than or equal to 10, the total number of benzene rings of the connecting part is less than or equal to 5, and the connection modes of the benzene rings are independently selected from ortho-position, meta-position and para-position.
The mass fraction of the acrylate group-containing fluoroboric pyrrole in the catalyst is in the range of 0.0001 to 10 wt%, preferably 0.01 to 5 wt%, more preferably 0.03 to 0.28 wt%.
Acrylate compound
The used acrylate compound aims at well fixing the BODIPY compound on a substrate in a covalent bond mode and realizing flexible adjustment of the content of a catalytic active site, namely BODIPY. Optionally, the acrylate compound is selected from one or more of dipropylene glycol diacrylate, glycidyl methacrylate, ethylene glycol dimethacrylate, ethoxylated trimethylolpropane triacrylate and trimethylolpropane triacrylate.
Morphology of catalyst
The catalyst is in a spherical structure, and the spherical structure is a hollow non-porous ball, a hollow porous ball, a solid non-porous ball or a solid porous ball.
The preparation method in the embodiment of the invention only provides a micro-fluidic method (different chips and different formulas can be used for preparing catalysts with different shapes, which are mentioned in detail later), and can also prepare micro-emulsion by a membrane emulsification method, an interfacial polymerization method, a layer-by-layer deposition method, a high-speed stirring emulsion preparation method, an ultrasonic emulsification method and other preparation methods, and then cure the micro-emulsion by an ultraviolet light curing means to obtain the multi-phase photocatalyst.
The synthesis method of the fluoboric pyrrole photosensitizer containing acrylate group refers to the following steps: sun, p.; wang, n.; jin, x.; zhu, x.acs appl.mater.interfaces 2017, 9, 36675-36687.
The preparation method of the BODIPY molecule refers to Loudet, A.; burgess, K.chem.Rev.2007, 107, 4891-4932; BODIPY is a common compound and is easily derivatized.
Preparation of monodisperse microdroplets
The micro-liquid drop constructed by the micro-fluidic chip is O/W type (using a coaxial flow type micro-fluidic chip) or W/O/W type (using a double coaxial flow type or flow focusing type micro-fluidic chip).
Fluoroboropyrroles
The used BODIPY compound is a BODIPY compound with acrylate groups, and when the BODIPY compound is used, the BODIPY compound is added into an oil phase, and the acrylate groups in the photosensitizer and the acrylate compounds are subjected to polymerization reaction under the irradiation of ultraviolet light. The technical scheme enables the photosensitizer to be connected with the polymer matrix through a covalent bond, the connection mode is more stable than the connection mode through intermolecular force, ionic bond, encapsulation, coating and other modes, the photosensitizer is not easy to run off, and the circulation stability of the heterogeneous catalyst is greatly improved.
Aqueous phase formulation
The water phase system used for constructing the micro-droplets is a surfactant aqueous solution. The surfactant is selected from Tween-20, sodium dodecylbenzenesulfonate, sodium dodecylsulfate, poloxamer, polyvinyl alcohol, and fluorinated solution. Preference is given to polyvinyl alcohols whose Mw can be 13000-23000, -31000, -47000, -67000, -145000, -205000. Optionally, the surfactant is present in a mass fraction of 0.1 to 30 wt%, preferably 1 to 15 wt%, more preferably 3 to 8 wt%.
Oil phase formula
An oil phase system for building microdroplets comprises a polymeric monomer and a photoinitiator. Optionally, the acrylate compound in the polymerized monomer is selected from one or more of dipropylene glycol diacrylate, glycidyl methacrylate, ethylene glycol dimethacrylate, ethoxylated trimethylolpropane triacrylate and trimethylolpropane triacrylate; the photoinitiator is selected from 2-hydroxy-2-methyl propiophenone, 2-hydroxy-4' - (2-hydroxyethoxy) -2-methyl propiophenone, 2-dimethoxy-2-phenyl acetophenone, and 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone. Specifically, for example, glycidyl methacrylate and trimethylolpropane triacrylate are used as an acrylate compound in the polymerization monomers, and 2-hydroxy-2-methyl propiophenone is used as a photoinitiator. As an embodiment, a phase separation agent may be added to the oil phase according to actual needs to form a channel structure when the droplets are solidified. The phase separating agent is selected from undecanol, hexadecane, 2-methylpentane, cyclohexanol, dodecanol, dioctyl phthalate, diisodecyl phthalate, etc.
Example 1
The hollow heterogeneous photocatalyst with a pore structure and containing 0.07 wt% of boron fluoride pyrrole.
The structure of the acrylate group-containing fluoroboric azole used in this example was
The preparation method of the catalyst described in this example is specifically as follows:
a heterogeneous photocatalyst containing 0.07 wt% of photosensitizer with a channel structure was prepared by a dual coaxial flow microfluidic chip (fig. 3). The aqueous phase was a 5 wt% aqueous solution of PVA-210 (Mw-67000). The formula of the oil phase is as follows: 1.31g of glycidyl methacrylate, 2.00g of trimethylolpropane triacrylate, 0.20g of 2-hydroxy-2-methylpropiophenone, 2.5mg of fluoroboric pyrrole and 1.50g of undecanol. Respectively introducing the oil phase solution and the water phase solution into the microfluidic chip through an injector and an injector pump, obtaining double-emulsion micro-droplets with the diameter of 450 mu m by adjusting the flow rate, and curing the double-emulsion micro-droplets through an ultraviolet lamp, wherein the outer diameter of the solidified double-emulsion micro-droplets is not obviously changed. And washing with deionized water and ethanol in sequence, and drying to obtain the heterogeneous photocatalyst with the pore structure.
The double emulsion micro-droplets prepared by the micro-fluidic chip are shown in figure 4a, the droplet size is uniform, and the monodispersity is high (c)v1.3%). The microdroplets were rapidly cured under the irradiation of ultraviolet light, and the fluorescence micrograph of the cured microspheres is shown in fig. 4b, where fluorescence is the luminescence of the BODIPY cured on the spheres.
The fluorescence spectrum of the section of the microsphere is obtained by a fluorescence confocal means, and the fluorescence spectrum is consistent with the luminescence of the BODIPY in the solution, so that the photosensitizer is confirmed to be polymerized on the microsphere. FIG. 5a is a confocal fluorescence micrograph of a cross section of a hollow microsphere, illustrating that the BODIPY active sites of the heterogeneous catalyst of the present invention are not only dispersed on the surface of the microsphere, but also uniformly distributed throughout the shell. FIG. 5c is a light intensity distribution diagram of the hollow microsphere in the diameter direction (the straight line position in FIG. 5 a), which shows that the BODIPY is uniformly distributed on the shell layer.
FIG. 6 is a scanning electron microscope image of the hollow microsphere and the cross section thereof under different scales, which confirms that the catalyst is a porous hollow microsphere.
FIG. 7 is a scanning electron microscope image of microspheres with only polymer matrix and their cross sections at different scales, which confirms that the addition of the photosensitizer BODIPY does not affect the pore structure of the polymer matrix.
Example 2
Acrylate polymers with different fluoroboropyrrole contents.
By varying the content of the fluoroboric pyrrole, the same polymer as the catalyst composition of example 1 was obtained, wherein the content of the fluoroboric pyrrole was 0.03, 0.07, 0.14 and 0.28% by weight, respectively. The UV-visible absorption spectra of the polymers with BODIPY contents of 0.03, 0.07, 0.14 and 0.28 wt% are shown in FIG. 8. As shown in fig. 8a, the absorbance increased with the increase in the amount of the BODIPY added, and the absorption peak shape and the maximum absorption peak position were not changed. FIG. 8b is a plot of BODIPY loading versus absorbanceAs can be seen, the loading and absorbance values in the range of 0.03-0.28 wt% are in accordance with Lambertian law, thus indicating that no aggregation of the photosensitizer occurs in this concentration range. We have studied the excited state properties of a polymer containing 0.07 wt% of fluoroboropyrroles, for example. Studies have shown that the rate of intersystem crossing of BODIPY from solution is 3.7X 10 after polymerization onto polyacrylate substrates9s-1Is raised to 2.7 multiplied by 1010s-1The triplet lifetime increased from 89 mus in solution to 1 ms. The improvement of the two properties is beneficial to the generation of intermolecular energy transfer in the photocatalysis process, and the construction of the catalyst with small load and high catalytic performance is realized. The above results demonstrate the adjustability of the mass fraction of the BODIPY in the catalyst, and demonstrate that the BODIPY can exert excellent photophysical properties in the catalyst, even improved compared with the solution.
Example 3
Hollow heterogeneous photocatalyst containing 0.07 wt% of boron fluoride pyrrole and having no pore structure.
The structure of the acrylate group-containing fluoroborole used in this example was the same as in example 1.
A heterogeneous photocatalyst containing 0.07 wt% of photosensitizer without a pore structure was prepared by a dual coaxial flow microfluidic chip (fig. 3). The aqueous phase was a 5 wt% aqueous solution of PVA-210 (Mw-67000). The formula of the oil phase is as follows: 1.31g of glycidyl methacrylate, 2.00g of trimethylolpropane triacrylate, 0.20g of 2-hydroxy-2-methylpropiophenone, 2.5mg of fluoroboric pyrrole. The oil phase solution and the water phase solution are respectively led into the micro-fluidic chip through an injector and an injector pump, double-emulsion micro-droplets with the diameter of 450 mu m are obtained by adjusting the flow rate, and are solidified through an ultraviolet lamp, and the outer diameter of the solidified micro-droplets is not obviously changed. And washing with deionized water and ethanol in sequence, and drying to obtain the heterogeneous photocatalyst without the pore channel structure.
Fig. 9 is scanning electron micrographs of hollow microspheres and their cross sections at different scales, confirming that the catalyst is non-porous hollow microspheres.
Example 4
Juglone was synthesized using the heterogeneous photocatalyst with 0.07 wt% of borofluoride pyrrole having a porous structure prepared in example 1.
Filling a heterogeneous photocatalyst with a pore structure and containing 0.07 wt% of boron fluoride pyrrole into a flow photoreactor, and carrying out the reaction of synthesizing juglone from 1, 5-dihydroxynaphthalene. In the reaction system, the concentration of 1, 5-dihydroxynaphthalene was 1.5X 10-4M, solvent dichloromethane/methanol 9/1(v/v), heterogeneous catalyst single layer arranged to fill the flow reactor, 20mW/cm2Visible light is used as a light source. The heterogeneous photocatalyst (fluoboric pyrrole, 0.07 wt%) participated in the flow synthesis of juglone yield (88%) and homogeneous reaction (fluoboric pyrrole, c is 1 × 10%-5M) were comparable, while the rate of the heterogeneous reaction was 0.896s-1This is 9.8 times the rate of the homogeneous reaction.
FIG. 10a demonstrates that the preparation method stabilizes the binding of the photosensitizer to the polymer matrix by covalent bonds and no leakage of the BODIPY is detected in the effluent. As shown in fig. 10b, the continuous flow synthesis of juglone using the heterogeneous photocatalyst can be maintained for 30 hours without yield reduction. The above proves that the heterogeneous photocatalyst prepared by the scheme has excellent photocatalytic performance.
Example 5
The preparation method of example 1 was used to replace the structure of the acrylate group-containing fluoroborole of example 1 with the following structure:
a heterogeneous photocatalyst with a pore structure containing 0.07 wt% of borofluoride pyrrole was obtained and applied to the synthesis of juglone from 1, 5-dihydroxynaphthalene described in example 4.
The effluent was analyzed by UV-visible absorption spectrometer to obtain juglone in 82% yield and a reaction rate of 0.746s-1This is 8.2 times the rate of the homogeneous reaction mentioned in example 4.
Example 6
The preparation method of example 1 was used to replace the structure of the acrylate group-containing fluoroborole of example 1 with the following structure:
a heterogeneous photocatalyst with a pore structure containing 0.07 wt% of borofluoride pyrrole was obtained and applied to the synthesis of juglone from 1, 5-dihydroxynaphthalene described in example 4.
The effluent was analyzed by UV-visible absorption spectrometer to obtain juglone in 64% yield and a reaction rate of 0.482s-1This is 5.3 times the rate of the homogeneous reaction mentioned in example 4.
Example 7
By using the preparation method of example 1, only the content of the borofluoride pyrrole was changed to obtain a heterogeneous photocatalyst having a pore structure and containing 0.28 wt% of the borofluoride pyrrole, which was applied to the oxidation reaction (aza-Henry reaction) of benzylamine.
Filling a heterogeneous photocatalyst with a pore structure and containing 0.28 wt% of boron fluoride pyrrole into a flow photoreactor to carry out photocatalytic oxidation on benzylamine. In the reaction system, the concentration of benzylamine was 1X 10-3M, solvent acetonitrile/dichloromethane 5/1(v/v), the heterogeneous catalyst was packed in a single layer arrangement in the flow reactor. The effluent was analyzed by gas-mass spectrometer to obtain a conversion of 100%.
Example 8
The oxidation reaction of terpinene (Alder-ene reaction) was carried out using the heterogeneous photocatalyst containing 0.28 wt% of borofluoride pyrrole having a porous structure prepared in example 7.
Filling a heterogeneous photocatalyst with a pore structure and containing 0.28 wt% of boron fluoride pyrrole into a flow photoreactor to carry out photocatalytic oxidation on terpinene. In the reaction system, the concentration of terpinene is 1X 10-3M, chloroform as solvent, and filling the flow reactor with heterogeneous catalyst in single layer. The effluent was analyzed by gas-mass spectrometer to obtain a conversion of 100%.
Example 9
The oxidation of p-toluenesulthiol (oxidation of thiol to dithiol) was carried out using the heterogeneous photocatalyst containing 0.28 wt% of fluoroborole having a pore structure prepared in example 7.
Filling the heterogeneous photocatalyst with a pore structure and containing 0.28 wt% of boron fluoride pyrrole into a flow photoreactor to carry out photocatalytic oxidation on the p-toluene thiophenol. In the reaction system, the concentration of p-toluene thiophenol is 1X 10-3M, the solvent is 1X 10-3M ethanol solution of triethylamine, and a heterogeneous catalyst is arranged in a single layer and filled in the flow reactor. The effluent was analyzed by gas-mass spectrometer to obtain a conversion of 95%.