Exploration On Pore-surface Micro-environment Regulation And Functional Applications Of Porous Organic Framework Materials

Porous organic frameworks(POFs),as an important branch of porous materials,are favored by numerous researchers for their excellent physical and chemical stability and abundant and varied pore structures.As the research hotspot,POFs provide such an important platform to achieve preset pore structures through a reasonable combination of building units and polymerization mechanisms,thus achieving excellent customized functions and applications.At present,POFs have shown an important position and bright application prospects in multiple fields such as catalysis,sensing,adsorption and separation,energy transmission and storage,and biomedicine.In view of the excellent structural properties of POFs,we take the micro-environment regulation of pore-surface of POFs as a foothold,and realize the multifunctional application of POFs as the guiding ideology,focusing on active sites,characteristic groups and coordination effects of POFs.We have researched the performance and application of POFs in the fields of proton conduction,gas adsorption and separation,and nonlinear optics.Accordingly,the main research content of this thesis includes the following four aspects:First focusing on the regulation of basic sites in the POF skeleton,we prepared the covalent triazine framework membranes(CTF-Mx)of superacid in-situ doped and studied their anhydrous proton conductivity over a wide temperature range.We show a simple and convenient way to prepare CTF-Mx with acid in-situ doping for anhydrous proton conduction in wide temperature range from subzero to elevated temperature(160°C).The low proton dissociation energy and continuous hydrogen bond network in CTF-Mx make the membrane achieving high proton conductivity from 1.21×10^-3 S cm^-1(-40°C)to 2.08×10^-2 S cm^-1(160°C)under anhydrous condition.Molecular dynamics and proton relaxation time analyses reveal proton activation by the regulation of basic sites at low activation energies with greatly enhanced mobility in the CTF membranes.Second focusing on the regulation of electron-rich groups in pore channels,we synthesized the polypyrene-hexadiyne porous organic framework for separation of semiconductor special gas.We designed a porous organic framework material with electron-rich groups(PD-POF).The sp-hybridized alkyne bridge?-conjugated POF has been formed with low density,high physical/chemical stability and excellent pore structures.The electron-rich groups can provide abundant active adsorption sites and regulate the charge transfer on pore structures the same as electron-withdrawing groups,thereby achieving efficient adsorption/separation of semiconductor electronic gas.In addition,fixed-bed breakthrough measurements and desorption tests prove that PD-POF has excellent capability of selective adsorption and cyclic regeneration.Third focusing on heavy metal ions coordination regulating the pore-surface charge density,we synthesized polyphthalocyanine porous organic frameworks for nonlinear optical properties.Phthalocyanine with an 18?-electron conjugated structure has intrinsic nonlinear optical response,while their agglomeration in solution and film between phthalocyanines is the bottleneck toward its optical limiting device processing.We developed three sp³-hybridized carbon bridge polyphthalocyanine porous organic frameworks(Pc-POFs)with an enhanced nonlinear absorption effect and optical limiting properties.The strong covalent bond linked porous structures in Pc-POFs could improve their optical limiting property by inhibiting the relaxation of the molecule and increasing their excited state absorption.Moreover,the Sn-Pc-POF which introducing Sn metal ion in phthalocyanine central,exhibited an optical limiting threshold of 0.37J/cm² at 532 nm nanosecond laser,which is highly competitive in comparison with state-of-art 2D optical limiting materials.Fourth focusing transition-metal ions coordination regulating the pore-surface electric field,we synthesized two-dimensional metal-polyphthalocyanine conjugated porous frameworks for promising optical limiting properties.Two-dimensional transition-metal-containing polyphthalocyanine conjugated porous frameworks(MPc-CPFs)synthesized and transition-metal(TM)ions ranging from Fe,Co,Ni,Cu and In are chose to combine in phthalocyanine centers to tune their delocalized electronic structure.The fully closed planar delocalized?-conjugated frameworks exhibit efficient nonlinear absorption and excellent optical limiting performance under ns pulse laser.In addition,the coordination of ferromagnetic transition metal ions(Co,Ni)in the center of phthalocyanine will produce resonance enhancement of nonlinear excited state absorption,which significantly improves the nonlinear optical response of MPc-CPFs.