Construction Of Heteroatom-containing Micronorous Polvmers And Their Gas Adsorption Properties

Microporous organic polymers are a class of porous adsorbent materials with high specific surface area,adjustable pore structure properties,low density,and excellent thermal and chemical stability,which have shown promising application prospect in gas storage,gas adsorption separation,and organic pollutant capture.In this paper,a series of microporous polymer materials containing rich polar heteroatoms(N,O,F)and metal ions(Fe2+)including polyaminal,fluorinated polymer and polyporphyrin are designed and synthesized based on pore structure control and heteroatom functionalization strategies.The influence of the spatial configuration,connecting arms and chemical composition of the building monomer on the specific surface area and pore structure parameters of the polymer was investigated.The relationship between the chemical composition and pore structure of the polymer and CO2 adsorption and separation,H2 storage and volatile organic vapor adsorption was further studied.The main research contents of the paper are as follows:(1)Triphenylamine functionalized ultramicroporous polyaminals were prepared though the polycondensation of triphenylamine-based aldehydes with melamine.This study shows that the rigid three-dimensional structure of triphenylamine is a key to the formation of ultra-microporous structure and the more aldehyde groups,the higher the porosity.The BET specific surface areas of TMPs are between 452-709 m2/g,their pore sizes are located at 0.52 nm,and the N content is high up to 42.88 wt%.TMPs show excellent CO2/N2 and CO2/CH4 selectivities of 186.6 and 23.7 at 273 K and 1.0 bar.Further,four microporous polyaminals MALPs with BET specific surface of 1093-1 179 m2/g were prepared through the polymerization of 1,4-bis(2,4-diamino-1,3,5-triazine)benzene and tetrahedral tetra(4-aldehydephenyl)methane,1,3,5,7-tetra(4-aldehydephenyl)adamantane,tetrakis(4-aldehydephenyl)silane and spirocyclic 2,2',7,7'-tetraaldehydespirobifluorene.The CO2 and H2 uptakes of MALPs are up to 18.6 wt%(273 K/1.0 bar)and 1.64 wt%(77 K/1.0 bar).In addition,MALPs also exhibit exceptional organic vapor adsorption capacities,and the benzene,cyclohexane and toluene vapors uptakes are up to 35.4 wt%,30.7 wt%and 35.7 wt%at 298 K and 0.1 P/Po relative pressure,respectively.(2)A tetraphenyladamantane-based octaaminotriazine with a rigid three-dimensional structure and a large internal molecular free volume was designed and synthesized.Through the aminal polymerization reaction,tetraphenyladamantyl microporous polyaminals with ultra-high specific surface area(1500-1779 m2/g)were prepared,which surpass all the reported polyaminals.Among them,Ad-MALP-2 has a largest micropore specific surface area of 1247 m2/g,and its CO2 and H2 uptakes reached 21.1 wt%(77 K/1.0 bar)and 2.18 wt%(77 K/1.0 bar).In addition,the microporous polyaminals with both aromatic and aliphatic structural units exhibited an extremely high organic vapor adsorption capacity.Even at 298 K and 0.1 P/P0 relative pressure,the uptakes of benzene,cyclohexane and toluene vapors reached 44.0 wt%,39.0 wt%and 38.8 wt%.(3)Baed on a tetrahedral 1,3,5,7-tetra(4-bromophenyl)adamantane,four fluorinated microporous polymers were prepared by C-H arylation reaction with fluoroaromatic hydrocarbons with different molecular structures.The results show that the greater the number of fluoroaromatic hydrocarbon connecting arms and the shorter the length,the higher the porosity of the polymer micropores formed.Among them,FMOP-4 constructed from 1,3,5-trifluorobenzene shows a BET specific surface area of up to 1373 m2/g,and the uptakes of CO2 and H2 are up to 12.2 wt%(273 K/1.0 bar)and 1.32 wt%(77 K/1.0 bar).In addition,the introduction of fluorine improves the hydrophobicity of the polymer backbone,and the strongly hydrophobic FMOPs exhibit excellent organic vapor adsorption properties.At 298 K and P/P0=0.9,the adsorption capacities of benzene,cyclohexane and toluene,n-hexane and methanol vapor reach 149.6 wt%,122.8 wt%,105.9 wt%,80.8 wt%and 76.7 wt%,respectively(4)Based on polyaldehydes with different spatial structures and chemical compositions,a series of microporous polyporphyrin PPNs with different topologies were prepared by solvothermal reaction with pyrrole.It is found that three-dimensional triphenylphosphine and spirobifluorene bulding blocks result in the formation of polyporphyrins with higher porosity,and the BET specific surface area of PPNs are in the range of 582 and 892 m2/g.The microporous polyporphyrin PPNs embracing rich heteroatoms(N,O)and Fe2+show very high CO2 adsorption heats(30.9-38.1 kJ/mol),and the CO2 uptakes can reach up to 17.6 wt%(273 K/1.0 bar),CO2/N2 and CO2/CH4 selectivities are up to 57.6 and 14.6.The H2 uptakes of PPNs are 1.15-1.44 wt%(77 K/1.0 bar),and the heats of adsorption reach 8.34-9.48 kJ/mol.