Preparation Of Novel Microporous Polymers And Their Applications

The porous materials have diverse potential applications in separation, heterogeneouscatalysis and gas storage. During the last few decades, the surge to develop such usefulmaterials has led the scientists to produce a number of novel porous materials such asmetal organic frameworks (MOFs), porous organic cages and microporous organicpolymers (MOPs), in addition to traditional porous materials such as zeolites and activatedcarbon etc. Among these porous materials, MOPs have some unique properties such aslarge surface area, low skeletal density and high chemical stability. Very recently, aparticular advantage of MOPs has attracted enormous scientific attention due to theirpotential to introduce a range of useful chemical functionalities within the porousframework. In these years, many approaches reported have aimed to develop newmicroporous organic materials with higher surface areas, controlled pore sizes andfunctions. However, the transition metal catalysts or noble metal catalysts used forsynthesis of CMPs, PAFs and some other MOPs are expensive and only lab-scale. It isoften also complicated to synthesize the monomers which must bear halogen, ethynyl orstereocontrolled structures such as spirocyclic monomers used in MOPs. Hence, thesustainable mass production of MOPs is an unanswered challenge.Accordingly, the main task of this PhD thesis is to explore some new versatilemethods to design and synthesize cost-effective and functional MOPs. Characterization ofthese MOPs was realized by nitrogen adsorption/desorption isotherms, solid-state NMRtechniques. Application of these MOPs as gas adsorption materials, heterogeneouscatalysts and toxic metal ion adsorbent were also exploited.Chapter I introduce the research background on microporous materials, andhighlighted the history of MOPs and their application in gas adsorption, heterogenouscatalysts, separation and purification and photoelectric filed.Chapter II describe the method to produce hypercrosslinked polymers (HCPs) with afair control over the pore size and the pore size distribution, and to generate polymer withuniform microporous structure eventually. The mechanism of DVB content controlling thepore structure is proposed. With the DVB content varying from0to10%, the pore size ofHCPs decreases, the pore size distribution become narrower and the micropore volumecontent increases from6.82to61.90%. When the DVB content is higher than7%, theHCPs changes to pure microporous organic polymer. The experimental data indicate that the smaller micropore size and higher microporous volume favor the H2and CO2gasadsorption.Chapter III and Chapter IV propose two kind of new method to synthesizecost-effective and functional MOPs. One method,‘knitting’ rigid building blocks with anexternal crosslinker, use a simple one-step Friedel-Crafts reaction of a low-cost crosslinkerwith ordinary, low functionality aromatic compounds to produce cost-effectivemicroporous polymers with very high surface areas and the only byproduct was methanol.The other method is based on Scholl reaction, a coupling reaction between two arenecompounds with the aid of a Lewis acid. This low-cost method can introduce a very broadvariety of functional groups or functional structures. This method suits for aryl ring, fusering or heterocyclic ring compound, hence, using this method can functionalize MOPs inextensive field, such as gas adsorption, photoelectricity and semiconductorChapter V describe the synthesis of uniform “Davankov-type” microporous polymernanoparticles via emulsion polymerization method and followed by a Friedel-Crafts-typehypercrosslinking. The particles size (39-131nm) are tunable via adjusting emulsifier dose.Friedel-Crafts-type hypercrosslinking reaction of the precursor yields monodispersenanoporous polymer nanoparticles (MPNs) with extremely high surface areas up to ca.1500m2/g (BET surface area). Moreover, MPNs present more micropore volume (0.56cm3/g), higher hydrogen adsorption capacity (1.59wt.%), higher hydrogen adsorptionisosteric heats and faster adsorption rate compared to polydisperse micro-size analogpreviously reported.In Chapter VI and VII, the two methods in Chapter III and Chapter IV are used tosynthesize two kind of MOPs with triphenylphosphine functional group respectively.These two kind functionalized MOPs coordinated with PdCl2are excellent heterogeneouscatalyst of Suzuki-Miyaura coupling reactions of aryl chlorides in aqueous media. Forvarious aryl halide and arylboronic acid, the heterogeneous catalysts all exhibit high yields.Moreover, these work demonstrate that the microporous polymer backbone knitting withphosphine ligand can efficiently disperse Pd to promote the catalytic activity, which ismuch higher than that of homogeneous catalysts under the similar conditions.In the last Chapter, sulfonic acid-modified microporous hypercrosslinked polymerssynthesized by sulfonation of microporous hypercrosslinked polymers have beeninvestigated as a high-capacity adsorbent for toxic metal ions. The results show that themodified resins retained their original microporous structure and spherical morphology,and possess sulfonic acid groups as hydrophilic groups and active sites. Sulfonic acids-modified materials have been found to attain very good adsorption capacity formetal ions, which is due to the synergic effect of microporous structure and active sites.The kinetic data obtained from of adsorption experiments supports a pseudo-second ordermodel and adsorption isotherms obtained at different temperatures are all fitted with theLangmuir isotherms. In addition, the thermodynamic parameters, i.e. Gibbs free energychange (△G0), enthalpy change (△H0), entropy change (△S0) of the adsorption processwere calculated, and the results confirmed the adsorption to be spontaneous andendothermic. Moreover, these modified resins can be recycled several times with minimalloss of adsorption capacity and thus may have potential industrial applications.