Method for preparing porous aromatic framework membranes based on inorganic salt template method
The present disclosure relates to the field of porous material synthesis, and particularly to a method for preparing porous aromatic framework membranes based on an inorganic salt template method. It aims at the problem of difficulty of preparation of porous aromatic framework membranes in large scale and large size. It uses alkynyl-containing building units and bromine-containing building units as raw materials and obtains continuous, dense, defect-free porous aromatic framework membranes through Sonogashira-Hagihara coupling polymerization. It specifically successfully prepares porous aromatic framework nanosheets on an inorganic salt substrate, and then produces a centimeter-scale large size continuous porous aromatic framework membrane through self-assembly. The method has mild conditions, a simple preparation process, and it is easy to operate. The prepared membranes have high yield and large area, and meet the requirements of actual industrial production.
1 . A method for preparing a porous aromatic framework membrane based on an inorganic salt template, comprising the following steps:
mixing an inorganic salt template, an alkynyl-containing building unit and a bromine-containing building unit, adding solvent and triethylamine to the mixture, and then adding catalyst under nitrogen protection, and mixing evenly to obtain a mixed solution; and
under nitrogen protection and liquid nitrogen, subjecting the mixed solution to a freeze-vacuum-thaw cycle, then heating the mixed solution to 60-150° C. for 48-96 hours to yield an inorganic salt layer, collecting the inorganic salt layer, and removing inorganic salt from the inorganic salt layer to obtain porous aromatic framework nanosheets, and then processing the porous aromatic framework nanosheets via a pressure-assisted method to obtain a porous aromatic framework membrane,
wherein the bromine-containing building unit is a bromine-containing organic monomer, the alkynyl-containing building unit is an alkynyl-containing monomer, and the numbers of bromine and alkynyl in the respective monomers are both greater than 1.
2 . The method for preparing a porous aromatic framework membrane based on an inorganic salt template according to claim 1 , wherein the bromine-containing building unit comprises 1,3,5-tribromobenzene, 1,3,5-tribromobenzene-2,4,6-triol, 1,4-dibromo-2-(methyl imidazole methyl ethyl) benzene, 1,3,5-tris (4-bromophenyl) benzene, tetrabromotetraphenylmethane, tris (4-(bromomethyl) phenyl) amine, 1,4-dibromobenzene, 2,4,6-tribromo-1,3,5-trimethylbenzene, tetra (4-bromomethylphenyl) ethylene, or 1,4-dibromo-2,5-diethylbenzene; and
the alkynyl-containing building unit comprises tris (4-ethynylphenyl) amine, 1,3,5-tris (4-ethynylphenyl) benzene, 5,10,15,20-tetrakis (4-ethynyl phenyl porphyrin), 1,3,5-triethynylbenzene, 1,4-diethynylbenzene, 4,4′-diethynylbiphenyl, tetrakis (4-ethynylbenzene) methane, 1,3,6,8-tetraethynylpyrene, or 3,3′,5,5′-tetraethynyl-1,l′-biphenyl.
3 . The method for preparing a porous aromatic framework membrane based on an inorganic salt template according to claim 1 , wherein a ratio of a mass of the inorganic salt template, an amount of the alkynyl-containing building unit, and an amount of the bromine-containing building unit is (10-20) g:(0.005-0.02) mmol:(0.005-0.02) mmol.
4 . The method for preparing a porous aromatic framework membrane based on an inorganic salt template according to claim 1 , wherein the inorganic salt template comprises a material selected from a group consisting of sodium chloride, potassium chloride, magnesium chloride, calcium chloride, aluminum chloride, sodium sulfate, magnesium sulfate, and potassium sulfate.
5 . The method for preparing a porous aromatic framework membrane based on an inorganic salt template according to claim 1 , wherein the solvent is selected from toluene, mesitylene, o-dichlorobenzene, N,N′-dimethylformamide, N,N′-dimethylacetamide, tetrahydrofuran, dichloromethane, triethylamine, and ethylenediamine.
6 . The method for preparing a porous aromatic framework membrane based on an inorganic salt template according to claim 1 :
wherein the bromine-containing building unit is 1,3,5-tribromobenzene and the alkynyl-containing building unit is tris (4-ethynylphenyl) amine to yield the following reaction formula of the porous aromatic framework membrane:
wherein the bromine-containing building unit is 1,3,5-tribromobenzene-2,4,6-triol and the alkynyl-containing building unit is tris (4-ethynylphenyl) amine to yield the following reaction formula of the porous aromatic framework membrane:
or wherein the bromine-containing building unit is 1,4-dibromo-2-(methyl imidazole methyl ethyl) benzene and the alkynyl-containing building unit is tris (4-ethynylphenyl) amine to yield the following reaction formula of the porous aromatic framework membrane:
wherein, n≥1.
7 . The method for preparing a porous aromatic framework membrane based on an inorganic salt template according to claim 1 , wherein a ratio of an amount of the bromine-containing building unit to a volume of the triethylamine is 0.01 mmol: 10-40 mL.
8 . The method for preparing a porous aromatic framework membrane based on an inorganic salt template according to claim 1 , wherein the catalyst is composed of tetrakis (triphenylphosphine) palladium and cuprous iodide, and a mass ratio of the tetrakis (triphenylphosphine) palladium to the cuprous iodide is 10-15:2-5; and a ratio of an amount of the bromine-containing building unit to a mass of the tetrakis (triphenylphosphine) palladium is 0.01 mmol: 10-15 mg.
9 . The method for preparing a porous aromatic framework membrane based on an inorganic salt template according to claim 1 , wherein the pressure-assisted method comprises a suction filtration operation.
10 . The method for preparing a porous aromatic framework membrane based on an inorganic salt template according to claim 1 , wherein removing the inorganic salt comprises: washing the inorganic salt layer with chloroform, methanol, and water.