Porous Organic Polymers Derived Energy Materials with Tunable Hierarchical Morphologies
Author:Zhang Wen Bei
organic porous polymers are widely used in photoelectric conversion,gas adsorption and separation,catalysis,energy storage and conversion,due to their high specific surface area,controllable pore structure,good chemical and thermal stability,and facile functionalization.And organic porous polymer materials can be synthesized facilely with certain dimension morphology.Herein,organic porous polymers with different morphologies and specific function were prepared by a series of condensation reaction.the results are summarized as follows:(1)We developed a facile synthetic method to prepare a series of Fe/N-doped hierarchical porous carbons with hollow structure by using conjugated microporous polymer and silica spheres as precursor and template respectively.The resulting carbon materials possess high surface areas and high content Fe/N co-doping characters,rendering them suitable for being as non-precious metal electrochemical catalysts for ORR reaction.The samples exhibited excellent electrochemical performance in comparison with the commercially available Pt/C catalysts.(2)Heteroazaporphyrinoids-based polymer nanosheets were synthesized and used as precursors in the fabrication of Fe/N/S-doped porous carbon nanosheets without any additon template.The resulting 2D carbon materials have relatively high surface area and Fe/N/S co-doping characteristics,making them suitable as non-precious-metal electrocatalyst for the ORR in both alkaline and neutral media.This study not only provides a new approach for the design and development of porous carbon nanosheets by using polymer nanosheet as precursor,but also offers porous carbon nanosheets with rich heteroatom and transition metal active sites as electrocatalysts for energy storage and conversion.(3)We utilize commercially available dianhydrides namely pyromellitic dianhydride(PMDA),naphthaene-1,4,5,8-tetracarboxylic dianhydride(NTCDA)and 3,4,9,10-Perylenetetracarboxylic dianhydride(PTCDA)as building blocks to polymerize with 1,3,5-benzene-tricarbohydrazide for fabricating dianhydride-based polyimides(PIs).The amino-groups of 1,3,5-benzene-tricarbohydrazide located on three directions could effectively build up expended cross-linked network.Stable and conjugated framework are polymerized by dynamic covalent bond.With the improvement on the electrochemical stability and electronic conductivity,these materials could afford more reactive sites for electrode-electrolyte interaction and accelerate electron and ion transportation during reversible sodiation/desodiation processes.As cathode for LIBs,the materials shows the characteristics of high capacity and long cycle life.(4)We report the template-free construction of a conjugated porous polymer microtube-fused bundles.In this process,driven by dynamic covalent chemistry of acylhydrazon linkage,the building blocks of 1,7-para-formylphenyl-perylene-3,4,9,10-tetracarboxylic imide and 1,3,5-benzene-tricarbohydrazide,featuring spatial spacer and curvature controls,were polycondensed to form microtubular skeletons preferentially,which were further woven to the surface-smooth microtubular bundles via the chaingrowth fusion either in individual-or inter-tubes.The resulting defined hierarchical morphology manifests the high shape persistence,co-used tubular walls and orientated sub-micrometer channels with tens of micron lengths,allowing for the full exposure of the elemental active sites,and the rapid transport of mass/charge.As the electrode materials in lithium/sodium-ion batteries,the as-synthesized porous polymer exhibited a high availability of redox active sites,with instant insertion/deinsertion of Li/Na ions during the charge/discharge process.