高内相乳液聚合法制备基于微孔有机网络的多级孔膜

The development of the environment, energy, food and medical industries has evoked the booming of the continuous flow analysis and reaction technology. The membrane material with adsorptive and catalytic functions is a major media for continuous flow technology. Currently, these functional membranes are mostly prepared by surface modification on commercial Ultrafiltration/Microfiltration （UF/MF）membranes and suffer from the trade-off relationship between the number of active sites and their approachability and low material tolerance. In order to address these challenges, we are going to synthesize hierarchical porous membranes via the high internal phase emulsion (HIPE) polymerization of monomers for microporous organic networks (MON). Based on the Sonogoshira cross-coupling reaction and the Schiff-base coupling reaction between melamine and polyaldehydes, we are able to prepare hierarchical porous Poly(phenylene ethynylene) (PPE) conjugated microporous polymer (CMP) via water/oil emulsion polymerizations and Shiff-base network (SNW) via nonpolar/polar organic emulsion polymerizations, respectively. In that case, macro/mesoporous channels, which are connected to the micropores formed by the crosslinking reactions of MON monomers, can be templated by the dispersed phase of the emulsions. Specific adsorptive or catalytic active sites for heterogeneous catalysis can be incorporated into micropores via copolymerization with functional monomers or post modifications. The resulted hierarchical porous membranes will be evaluated as materials for solid phase extraction and solid phase synthesis, whose performance can be synergistically optimized by an orthogonal modulation of the porous structure by tuning the emulsion polymerization reactions addressing the macro/meso pores and tuning the monomer structure addressing the micropores. We believe the superiority of MONs on surface area and chemical stability and the superiority of polyHIPEs on transport efficiency and membrane flux can be synergized by the method put forward in this proposal towards novel adsorptive and catalytic polymer membranes.

环境、能源、食品、医药等行业的发展，促发了连续流分析与反应技术的兴起。具有吸附和催化功能的膜材料是一类重要的连续流介质，目前主要通过修饰超微滤膜制得，存在活性位点的负载量与扩散效率无法兼顾以及耐受性低等瓶颈问题。鉴于此，本项目以合成微孔有机网络（MON）的单体为原料，用高内相乳液（HIPE）聚合制备多级孔膜。基于Sonogoshira偶联反应和三聚氰胺-多醛偶联反应，分别通过水/油乳液聚合和非极性/极性有机乳液聚合制备多级孔聚苯乙炔和席夫碱网络。用乳液分散相为模板构筑大（介）孔流道，用MON刚性单体的交联搭建微孔；通过与功能单体共聚和后修饰，在微孔中引入特异性吸附和非均相催化位点；利用乳液聚合条件和单体结构分别对大（介）孔和微孔进行正交调控，优化膜材料固相萃取和合成催化性能。本项目可望结合MON的大比表面积、高化学稳定性和polyHIPEs的高传质效率、大通量，制备新一代吸附膜和催化膜。

表面修饰是制备吸附、催化等功能膜的主要方法。通过在超微滤膜表面接枝引入功能基团，膜材料的功能是通过膜孔中的功能位点与目标物（底物）的相互作用来实现的，功能位点的密度决定了功能膜的（吸附或催化）容量，可接近性决定了传质效率。但是，现有聚合物商品膜比表面积低，通过表面修饰引入的“活性位点容量”与“膜材料孔容量、膜通量以及传质效率”之间存在明显的trade-off关系。因此，本项目力求设计制备兼具微孔、介孔和大孔的多级孔膜材料，利用微孔提供吸附、催化活性位点，利用大孔提供对流传质通道，解决活性位点容量与传质效率之间的矛盾关系。.项目重点研究了以合成微孔有机网络（MON）的单体为原料，用高内相乳液（HIPE）聚合制备多级孔膜的方法。首先，以三聚氰胺和多聚甲醛作为反应单体，以二甲基亚砜(DMSO)为连续相溶剂，以异构烷烃Isopar M为分散相溶剂，以F127为表面活性剂，通过高内相乳液聚合，一步法制备了兼具微孔、介孔、大孔的多级孔聚三聚氰胺甲醛PMF，用于催化CO2与环氧化合物的加成反应，在100℃，2 MPa，在Zn@ah-PMF催化的环氧丙烷环加成催化反应中，0.5 h的转化率可达79.1%，TOF值高达18388 h-1，比当时已经报道的催化剂的TOF值高出6-100倍，验证了设计多级孔膜兼具高活性位点容量和高传质效率的设想。但是，单纯用基于MON的polyHIPEs制膜，容易粉化，无法实现连续流反应（分离）。因此，尝试将PMF 与制膜聚合物共混，相转化制膜，制得具有连续流催化功能的多级孔膜，并在此基础上发展了一系列可以正交调控微孔和大孔，制备多级孔膜材料的方法，包括1）以自具微孔聚合物为制膜原料，采用溶液相转化法制备多级孔膜；2）将大孔化合物、微孔材料接枝到大孔膜表面；3) 成膜与聚合物与多（极）孔材料相转化共混制膜等。制得膜材料用于CO2催化和水体内微量污染物过滤脱除/分离，总结了一些多级孔膜构效关系规律。.项目组已经在ACS Catalysis, J. Mater. Chem. A, Chem. Eng. J，J. Membr. Sci., Appl. Surf. Sci., Sep. Purif. Technol.等膜材料及催化领域国际知名刊物上发表SCI论文18篇，申请中国专利5项，目前授权2项，完成了成果指标。