Preparation And Properties Of Hierarchically Porous Monoliths

The hierarchically porous materials are a novel kind of materials with multi-sized porous structure. They are developed from the microporous, mesoporous and macroporous materials, recently. Hierarchically porous materials have various physical and chemical characteristics of pores at different scales, and show a highly potential application value as adsorbent, catalyst carrier, microreactor unit and sensing materials. This thesis is mainly launched a series of studies focusing on the fabrication and surface property adjustment of hierarchically porous materials. It is an effective approach to improve the novel function by the dual coupling from structure and surface. The main research results are as follows:(1) Monolithic silica (HPS) with interconnected hierarchical pores is prepared via "Chemical cooling". By the effective adjustment of surface wettability, the modified-HPS can selectively remove the oil pollutions in water. The hydrophobic HPS is also able to remove the microemulsion droplets and emulsifier molecules, and shows remarkable demulsification performance for stable emulsion. Experimental results show that:It is an important means to construct the oil-water separation materials with good selectivity, high adsorbance and well stability by combining the hierarchically porous structure with the controllable surface wettability.(2) Monolithic hierarchically porous carbon (HPC) is fabricated by a facile dual-templating approach and sol-gel process. The HPC to reveal high specific capacitance value and electrochemical stability as the electrode materials of supercapacitor. The liquid and proton transfer inside the pore channels can be controlled by surface modification. The specific capacitance value of modified HPC can reach up to404F g-1. Furthermore, a series of composite electrode materials can be obtained via depositing conducting polymers on the HPC surface with electrochemical polymerization. The specific capacitance value can reach1488F g-1at maximum. Meanwhile, such composited materials also show considerable electrochemical stability, with at least76.7%of the capacitance being retained after1000cycles.(3) Using the HPS as the solid-reactor, the crystallization process of different materials inside the pore can be controlled via the adjustment of surface chemical properties. Experiments show that there are especial enthalpy change and short-range ordered crystal structure for higher aliphatic hydrocarbon inside the pore channels modified with long-chain alkyl groups. It is able to improve the energy storage capacity. Basing on the conclusion above, hierarchically porous graphite (HPG) monolith is fabricated through confined graphitizing process with FeCl3as the catalyst and HPS as reactor. It balances the benefits of porous structure and degree of crystallization. There is deep signification to construct other inorganic materials with both high crystallinity and high porosity.(4) On the basis of HPS, a facile approach is developed for the construction of durable and reusable microreactors in flow. The silica scaffold with macro-and mesoporous structure suffers from surface modification by the growth of pyrogallol (PG) polymer, followed by in-situ reduction and immobilization of Au nanoparticles (AuNPs). The as-prepared microreactors show high catalytic performance in the reduction of4-nitrophenol (4-NP). More importantly, the easily handling, low-cost and eco-friendly synthetic strategy can be extended to other noble metals and substrates for various reactions.