Nitrogen-doped mesoporous carbon-coated titanium dioxide composite photocatalyst, a preparation method and use thereof

Abstract

The invention discloses a nitrogen-doped mesoporous carbon-coated Titanium dioxide composite photocatalyst, a preparation method and use thereof. The preparation method comprises the steps of: dissolving an organic ligand and Ti(OC.sub.3H.sub.7).sub.4 in a mixture of methanol and DMF at a certain ratio, performing a hydrothermal reaction, centrifuging and drying to obtain a Titanium-based metal organic framework (Ti-MOF); pyrolyzing the obtained Ti-MOF under an inert atmosphere, and oxidizing the same for etching to obtain a nitrogen-doped mesoporous carbon-coated Titanium dioxide composite photocatalyst. The obtained composite photocatalyst not only facilitates the adsorption, enrichment and mass transfer of low concentration VOCs, but also efficiently degrades VOCs under sunlight. It has high degradation activity and stability when performing photocatalytic removal of VOCs in the presence of visible light, is simple in synthesis, low in preparation cost, and has strong potential for the use in environmental protection.

Claims

1. A method for preparing a nitrogen-doped mesoporous carbon-coated Titanium dioxide composite photocatalyst, characterized in that it comprises the steps of: S1. mixing an organic ligand, Ti(OC.sub.3H.sub.7).sub.4, methanol and DMF into a reaction vessel with polytetrafluoroethylene; S2. placing the reaction vessel containing the mixed solution in S1 in an oven, rising the temperature to 120-160° C., maintaining this temperature for 24-72 hours, and then cooling to room temperature to obtain a precipitate; S3. cross washing the precipitate obtained in S2 with an alcohol and DMF, centrifuging, and drying under vacuum to obtain an activated Titanium-based MOF material; S4. heating the activated Titanium-based MOF material obtained in S3 to 500-800° C. in an inert gas atmosphere and maintaining the temperature for 2-12 h; after lowering the temperature to 300-500° C., replacing the inert gas with a weak oxidizing gas; maintaining the condition for 30-120 min, adjusting the atmosphere back to the original inert gas atmosphere and the temperature to room temperature, so as to prepare a nitrogen-doped mesoporous carbon-coated TiO.sub.2 composite photocatalyst.

2. The method for preparing a nitrogen-doped mesoporous carbon-coated Titanium dioxide composite photocatalyst according to claim 1, characterized in that the organic ligand in S1 is a mixture of 2-aminoterephthalic acid and terephthalic acid or 2-aminoterephthalic acid alone.

3. The method for preparing a nitrogen-doped mesoporous carbon-coated Titanium dioxide composite photocatalyst according to claim 1, characterized in that the molar ratio of the organic ligand, Ti(OC.sub.3H.sub.7).sub.4, methanol and DMF in S1 is 3:2: (23-25): (118-120).

4. The method for preparing a nitrogen-doped mesoporous carbon-coated Titanium dioxide composite photocatalyst according to claim 1, characterized in that the rate of said rising temperature in S2 is 0.1-10° C/min.

5. The method for preparing a nitrogen-doped mesoporous carbon-coated Titanium dioxide composite photocatalyst according to claim 1, characterized in that the alcohol in S3 is methanol or ethanol.

6. The method for preparing a nitrogen-doped mesoporous carbon-coated Titanium dioxide composite photocatalyst according to claim 1, characterized in that said drying under vacuum in S3 is carried out under 100-170° C. for 8-24 h.

7. The method for preparing a nitrogen-doped mesoporous carbon-coated Titanium dioxide composite photocatalyst according to claim 1, characterized in that the inert gas in S4 is Ar or N.sub.2, and the weak oxidizing gas is CO.sub.2 or air; the rate of said heating is 1-10° C/min, and the rate of said lowering temperature is 1-10° C/min.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a kinetic curve of adsorption and photocatalytic degradation of gas phase styrene by a nitrogen-doped mesoporous carbon-coated TiO.sub.2 (TiO.sub.2@NC) composite photocatalyst in Example 1.

(2) FIG. 2 is an XRD pattern of TiO2@C—N showing various characteristic peaks at 2θ.

DETAILED EMBODIMENT

(3) The contents of the present invention are further described below in conjunction with the specific embodiments, but are not to be construed as limitation of the invention. The technical means used in the examples are not conventionally known to those skilled in the art, unless otherwise specified. Unless otherwise indicated, the reagents, methods, and devices employed in the present invention are routine reagents, methods, and devices in the art.

Example 1

(4) 1. Preparation of Photocatalytic Material

(5) S1. Mix 2-aminoterephthalic acid, Ti(OC.sub.3H.sub.7).sub.4, methanol and DMF at a molar ratio of 3:2:23:118 and add them to a reaction vessel with polytetrafluoroethylene;

(6) S2. Place the reactor in an oven, set the program, raise the temperature to 150° C. at a rate of 1° C./min, then maintain the temperature for 48 h, finally cool down at a rate of 5° C./h down to room temperature to obtain a precipitate;

(7) S3. Cross wash the precipitate obtained in S2 with methanol and DMF, conduct centrifugation and vacuum drying at 150° C. for 12 h to obtain an activated Titanium-based MOF material;

(8) S4. Place the activated Titanium-based MOF material prepared in S3 in a tube furnace, raise the temperature from room temperature to 600° C. at a rate of 1° C./min under Ar atmosphere, and maintain this temperature for 6 h; then, lower the temperature to 500° C. at a rate of 1° C./min and keep it for 30 min, during which Ar is replaced with CO.sub.2; finally, adjust the atmosphere back to Ar atmosphere, and reduce the temperature to room temperature at a rate of 1° C./min to obtain a nitrogen-doped mesoporous carbon-coated TiO.sub.2 composite photocatalyst.

(9) 2. Performance Test:

(10) FIG. 1 is a kinetic curve of adsorption and photocatalytic degradation of gas phase styrene by a nitrogen-doped mesoporous carbon-coated TiO.sub.2 composite photocatalyst according to the present example. It can be seen from FIG. 1 that the adsorption rate of styrene reaches 91.7% within 60 min, and the degradation rate of gas phase styrene reaches 74.5% within 80 min. The results show that the photocatalyst has good adsorption and photocatalytic activity, and the one treated by weak oxidizing gas exhibits better effect. The nitrogen-doped mesoporous carbon-coated TiO.sub.2 composite photocatalyst prepared by the invention is a novel material with high adsorption and photocatalytic activity.

Example 2

(11) S1. Mix 2-aminoterephthalic acid, Ti(OC.sub.3H.sub.7).sub.4, methanol and DMF at a molar ratio of 3:2:23:118 and add them to a reaction vessel with polytetrafluoroethylene;

(12) S2. Place the reactor in an oven, set the program, raise the temperature to 150° C. at a rate of 5° C./min, then maintain the temperature for 72 h, finally cool down at a rate of 5° C./h down to room temperature to obtain a precipitate;

(13) S3. Cross wash the precipitate obtained in S2 with methanol and DMF, conduct centrifugation and vacuum drying at 120° C. for 24 h to obtain an activated Titanium-based MOF material;

(14) S4. Place the activated Titanium-based MOF material prepared in S3 in a tube furnace, raise the temperature from room temperature to 700° C. at a rate of 2° C./min under Ar atmosphere, and maintain this temperature for 7 h; then, lower the temperature to room temperature at a rate of 2° C./min to obtain a nitrogen-doped mesoporous carbon-coated TiO.sub.2 composite photocatalyst.

Example 3

(15) S1. Mix 2-aminoterephthalic acid, Ti(OC.sub.3H.sub.7).sub.4, methanol and DMF at a molar ratio of 3:2:23:118 and add them to a reaction vessel with polytetrafluoroethylene;

(16) S2. Place the reactor in an oven, set the program, raise the temperature to 150° C. at a rate of 1° C./min, then maintain the temperature for 48 h, finally cool down at a rate of 5° C./h down to room temperature to obtain a precipitate;

(17) S3. Cross wash the precipitate obtained in S2 with methanol and DMF, conduct centrifugation and vacuum drying at 150° C. for 8 h to obtain an activated Titanium-based MOF material;

(18) S4. Place the activated Titanium-based MOF material prepared in S3 in a tube furnace, raise the temperature from room temperature to 500° C. at a rate of 3° C./min under Ar atmosphere, and maintain this temperature for 9 h; then, lower the temperature to 300° C. at a rate of 3° C./min and keep it for 60 min, during which Ar is replaced with CO.sub.2; finally, adjust the atmosphere back to Ar atmosphere, and reduce the temperature to room temperature at a rate of 3° C./min to obtain a nitrogen-doped mesoporous carbon-coated TiO.sub.2 composite photocatalyst.

Example 4

(19) S1. Mix 2-aminoterephthalic acid, Ti(OC.sub.3H.sub.7).sub.4, methanol and DMF at a molar ratio of 3:2:25:120 and add them to the reaction vessel with polytetrafluoroethylene;

(20) S2. Place the reactor in an oven, set the program, raise the temperature to 160° C. at a rate of 10° C./min, then maintain the temperature for 24 h, finally cool down at a rate of 5° C./h down to room temperature to obtain a precipitate;

(21) S3. Cross wash the precipitate obtained in S2 with methanol and DMF, conduct centrifugation and vacuum drying at 150° C. for 20 h to obtain an activated Titanium-based MOF material;

(22) S4. Place the activated Titanium-based MOF material prepared in S3 in a tube furnace, raise the temperature from room temperature to 800° C. at a rate of 10° C./min under nitrogen atmosphere, and maintain this temperature for 2 h; then, lower the temperature to 500° C. at a rate of 5° C./min and keep it for 90 min, during which nitrogen is replaced with CO.sub.2; finally, adjust the atmosphere back to nitrogen atmosphere, and reduce the temperature to room temperature at a rate of 5° C./min to obtain a nitrogen-doped mesoporous carbon-coated TiO.sub.2 composite photocatalyst.

Example 5

(23) S1. Mix 2-aminoterephthalic acid, Ti(OC.sub.3H.sub.7).sub.4, methanol and DMF at a molar ratio of 3:2:25:120 and add them to the reaction vessel with polytetrafluoroethylene;

(24) S2. Place the reactor in an oven, set the program, raise the temperature to 120° C. at a rate of 0.1° C./min, then maintain the temperature for 72 h, finally cool down at a rate of 5° C./h down to room temperature to obtain a precipitate;

(25) S3. Cross wash the precipitate obtained in S2 with methanol and DMF, conduct centrifugation and vacuum drying at 170° C. for 16 h to obtain an activated Titanium-based MOF material;

(26) S4. Place the activated Titanium-based MOF material prepared in S3 in a tube furnace, raise the temperature from room temperature to 600° C. at a rate of 2° C./min under Ar atmosphere, and maintain this temperature for 12 h; then, lower the temperature to 500° C. at a rate of 2° C./min and keep it for 120 min, during which Ar is replaced with CO.sub.2; finally, adjust the atmosphere back to Ar atmosphere, and reduce the temperature to room temperature at a rate of 10° C./min to obtain a nitrogen-doped mesoporous carbon-coated TiO.sub.2 composite photocatalyst.

Example 6

(27) S1. Mix 2-aminoterephthalic acid, Ti(OC.sub.3H.sub.7).sub.4, methanol and DMF at a molar ratio of 3:2:25:120 and add them to the reaction vessel with polytetrafluoroethylene;

(28) S2. Place the reactor in an oven, set the program, raise the temperature to 120° C. at a rate of 1° C./min, then maintain the temperature for 72 h, finally cool down at a rate of 5° C./h down to room temperature to obtain a precipitate;

(29) S3. Cross wash the precipitate obtained in S2 with methanol and DMF, conduct centrifugation and vacuum drying at 150° C. for 8 h to obtain an activated Titanium-based MOF material;

(30) S4. Place the activated Titanium-based MOF material prepared in S3 in a tube furnace, raise the temperature from room temperature to 600° C. at a rate of 2° C./min under Ar atmosphere, and maintain this temperature for 5 h; then, lower the temperature to 300° C. at a rate of 2° C./min and keep it for 30 min, during which nitrogen is replaced with air; finally, adjust the atmosphere back to nitrogen atmosphere, and reduce the temperature to room temperature at a rate of 5° C./min to obtain a nitrogen-doped mesoporous carbon-coated TiO.sub.2 composite photocatalyst.

(31) The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited thereto, and any other changes, modifications, substitutions, combinations, combinations and simplification made thereof made without departing from the spirit and scope of the invention should all be equivalent replacements and are included in the scope of the present invention.