New Preparation Methods And Properties Of Heteroatomic Porous Organic Polymers

Porous organic polymers（POPs）have attracted widespread attention in fields such as adsorption and catalysis due to their high Brunauer-Emmet-Teller（BET）specific surface area(S_BET),unique pore structure,and diverse chemical structures.Bonding heteroatoms such as nitrogen,oxygen,and sulfur onto the framework of POPs can introduce acid-base interactions,coordination interactions,hydrogen bonding,and dipole interactions in the adsorption and catalytic processes,thereby improving the performance of POPs.Therefore,new synthesis strategies are adopted to prepare heteroatom functionalized POPs with high specific surface area and unique pore structure,and to explore the structure-activity relationship between synthesis,structure,adsorption,and catalytic properties,it has important academic value for developing new types of POPs and expanding their application fields.Therefore,this paper explored new methods for preparing POPs,constructs a series of heteroatom functionalized POPs,studied the chemical and pore structures of POPs,and systematically studied their applications in adsorption and CO₂photocatalytic reduction.The main contents are as follows:（1）The melamine（MA）knitted polymer PMA was prepared by Schiff base reaction of aromatic monoketone,diketone and triketone with MA using dimethyl sulfoxide（DMSO）as solvent.The study of reaction mechanism shows that DMSO first decomposes into formaldehyde and then condensates with MA to form intermediates.Further,PMA was prepared by inserting aromatic ketones into polymer chains of intermediates by Schiff base reaction.Moreover,the pore structure of PMA can be effectively regulated by regulating the amount of carbonyl group of aromatic ketone and the amount of MA added.PMA-3-8 has the highest S_BET（772 m²/g）and pore volume(V_total,0.82 cm³/g),showing excellent CO₂ adsorption（171 mg/g,298 K/1.0 bar）and Hg²⁺removal performance（equilibrium adsorption capacity:702 mg/g）（2）A rich carbonyl-containing polymer TPA-TPC was prepared by Friedel Crafts acylation reaction using a mixture of carbon disulfide（CS₂）and nitrobenzene（Ph NO₂）as solvent,（CF₃SO₃）₂Sn as catalyst,and triphenylamine（TPA）and terephthaloyl chloride（TPC）as precursors.The results showed that the solvent played a key role in the preparation of TPA-TPC.TPA-TPC（3/1）prepared with 3:1 ratio of CS₂ to Ph NO₂ has suitable S_BET,V_total（446 m²/g and 0.21 cm³/g）and abundant carbonyl group.Furthermore,the polymer TPA-TPC-MA was functionalized with MA,and had high S_BET（680 m²/g）,V_total（1.01 cm³/g）and nitrogen content（50.04at.%）.The adsorption experiments showed that TPA-TPC-10MA with the highest V_total（1.01 cm³/g）could effectively adsorb iodine vapor（505 wt.%）,while TPA-TPC-8MA with the highest nitrogen content（50.04 at.%）could effectively remove Hg²⁺（equilibrium adsorption capacity:781 mg/g）.（3）Using TPA,1,3,5-triphenylbenzene（TPB）and triphenylmethane（TPM）as precursors and TPC as the acylation reagent,POPs（TPA-TPC,TPB-TPC and TPM-TPC）containing abundant carbonyl groups were prepared under solvent-free conditions by a trifluoromethanesulfonic acid（TFA）vapor catalyzed method.It was found that varying the reaction time,temperature and TFA addition could modulate the pore structure of POPs,and the S_BET of TPA-TPC,TPB-TPC and TPM-TPC could reach 357 m²/g,505 m²/g and 362 m²/g,respectively,which were much higher than those of the polymers prepared by the solvothermal method.Particularly,no coupling reaction of the precursor itself occurs in this method,which provides a new idea for Friedel-Crafts acylation for efficient and rapid preparation of POPs containing abundant carbonyl groups.（4）The triazine-based polyporphyrin CTF-PP was prepared,using 5,10,15,20-tetra（4-cyanophenyl）porphyrin as monomers which were self-polymerized under solvent-free conditions by TFA vapor catalysis.The results showed that the structure of the porphyrin ring in CTF-PP prepared by TFA vapor catalyzed method conditions was effectively retained and the catalyst could be removed readily compared with the ionothermal method.The S_BET of CTF-PP prepared by the catalytic reaction of 75μL TFA at270°C for 24 h reached 523 m²/g,and the pore distribution was mainly microporous.The photoelectric performance test results showed that CTF-PP could effectively adsorb CO₂（114 mg/g,298 K/1.0 bar）and photocatalytically reduce CO₂ to CO with a 4 hours yield of 41.5μmol/g.（5）Organic-inorganic hybrid materials Bi WO@CTFs with core-shell structures were prepared by mixing Bi₂WO₆ with 1,4-dicyanobenzene under solvent-free conditions using a vapor-catalytic method.From the results,it was found that the inorganic Bi₂WO₆ and organic CTFs form a type II heterojunction at the interface through the coordination between nitrogen atoms and metals,which improves the photoelectric performance of the material.The photocatalytic reduction of CO₂ to CO has excellent performance,and the rate of CO formation of Bi WO@CTF-10 reached32.8μmol/（g·h）.Through the analysis of the energy band structure,it is hypothesized that the type-II heterojunction generated in the hybrid material can effectively separate the photogenerated carriers and electron holes,accelerate the electron migration rate,and enhance the photocatalytic performance.