pH开关型高效Pickering乳液体系构建及界面催化效应研究

Catalyst nanoparticles with properly hydrophobic surface can stabilize oil or water droplets in an organic/aqueous biphasic system (these particles are considered to have interfacial activity), forming a Pickering emulsion catalysis system. Due to its reaction interface area, Pickering emulsion catalysis system has high catalysis efficiency. However, as an emerging catalysis research direction, the reported Pickering emulsion systems yet suffer from the poor stability at high temperature due to the thermo-induced droplet coalesence, and difficulty in separating nanocatalysts adsorbed strongly on the emulsion droplets surface. To this end, this application will prepare pH-responsive, efficient, interfacially active catalysts, and thereby construct a novel Pickering emulsion catalysis system that is stable at high temperature but able to demulsify at room temperature, so as to realize high reaction efficiency and in situ recycling nanocatalysts. Furthermore, using aqueous hydrogenation as model reaction, the application will elaborate the underlying correlations among catalyst surface properties, catalyst structures, emulsion properties and catalytsis efficiency. Also, the application will attempt to build the intrinsic relations between catalytic selectivity and microscopic information on the Pickering emulsion interface including reactant molecule orientation and molecule hydrogen bonding.

具有适当疏水性的纳米催化剂颗粒能稳定油水双相体系中的油滴或水滴（该纳米颗粒被认为具有界面活性），形成Pickering乳液催化体系，巨大的反应界面使其具有高催化效率。然而，作为新兴的研究方向，该体系尚存在着高温下因剧烈热运动发生乳滴聚并、室温下因纳米催化剂强吸附在乳滴表面而不易分离的问题。为此，申请拟制备pH响应的高效界面活性纳米催化剂，以构建一个高温下能形成稳定乳液、室温下易破乳的新型催化体系，进而实现高的反应效率和纳米催化剂的原位分离再循环使用。在此基础上，以水相加氢反应为例，阐述催化剂表面性质、催化剂结构、乳液性质与催化效率之间相互关联的科学问题，并试图建立催化选择性与Pickering乳液界面上反应物分子取向、分子氢键等微观信息的内在联系。

项目针对目前国际上Pickering乳液催化体系破乳困难而导致催化剂难以分离的瓶颈问题，开展了具有pH开关功能的高效Pickering乳液体系构建及界面催化效应研究。取得的重要进展主要包括：（1）发展了同时具有pH响应能力和亲疏水性可连续调控的SiO2表面修饰方法，构建了pH-响应型的Pickering乳液催化体系及Pickering微泡催化体系，将加氢反应催化效率提高2-9倍，实现了pH诱导Pickering乳液破乳；（2）成功合成了pH-响应型和双组份Janus界面活性颗粒，构建了Janus颗粒稳定的Pickering乳液催化体系，通过离心方法从实验上证实了该乳液体系的高稳定性，阐明了Janus颗粒结构、乳液性质与催化效率之间的关系，同时通过控制金属纳米粒子在Janus颗粒上区域分布，显著提高了两相反应体系催化反应效率；（3）提出Pickering乳滴固定床催化体系，实现了酶催化反应2000小时连续运行，避免Pickering乳液体系催化剂的分离过程。这些研究工作，突破了传统Pickering乳液催化体系的瓶颈，解决了催化剂特别是酶催化效率、循环使用、连续反应等关键问题，为精细化学品的绿色催化合成奠定了理论与技术基础。相关研究成果发表在 JACS, Angew, Langmuir, 催化学报、Chinese Chemical Letters等期刊上，被Nature和C＆EN 等核心刊物亮点报道。在国内外重要学术会议上作邀请报告10余次，培养了2名博士研究生和5名硕士研究生，并与英国Hull大学Bernard Paul Binks教授和英国 Leeds大学Rammile Ettelaie副教授开展了深入合作，提升了研究团队的创新能力，在国内外产生积极学术影响。