多功能锆基MOFs的构筑和晶体缺陷调控及其串联反应协同催化机理研究

Metal-organic frameworks (MOFs) embedded with catalytic units are excellent candidates for heterogeneous catalysis. Despite numerous studies, it is still highly desirable, yet challenging, to synthesize MOF-based catalysts with high density of active sites, excellent chemical stability, and controllable defects. Moreover, the synergetic effect between the installed catalytic units and defects toward catalytic reaction is far from being well understood. In this project, we demonstrate the preparation of a robust TEMPO radical and -NH2 decorated Zr-MOF, by covalent incorporation of TEMPO radical moiety and -NH2 group into a terphenyl-4,4’-dicarboxylic acid ligand and with employment of Zr (IV) as metal node. The use of monocarboxylic acid as modulators are expected to precisely control the defects of Zr-MOFs, through systematical investigation of defects by FT-IR, BET, TGA and EPR. We use selective oxidation of alcohol to its corresponding aldehyde, together with Knoevenagel condensation as a tandem reaction, to evaluate the catalytic activity of TEMPO radical and –NH2 functionalized Zr-MOFs. This study will help to fill the gap of synergistic effect between installed catalytic units and defects, and opens new routes to design highly active and stable MOF catalysts, for example, through defects engineering of metal nodes by modulators, surfactants, and mixed-linker strategy.

设计合成多功能、高密度催化位点、良好化学稳定性MOFs对拓展MOFs在催化领域应用极为重要。MOFs晶体缺陷具有提升MOFs催化性能作用。目前，多功能MOFs的合成以及MOFs晶体缺陷精确调控方面仍面临挑战；MOFs官能团和晶体缺陷协同催化机理亟待解决。本项目提出以Zr-MOFs为平台，采用有机配体侧链引入官能团方式，在三联苯二羧酸侧链嫁接TEMPO自由基和-NH2基团，合成H2tpdc-TEMPO和H2tpdc-NH2，并利用混合配体策略，构筑多功能Zr-MOFs。以单羧酸有机酸为调节剂，利用FT-IR、BET、TGA和EPR等技术系统研究Zr-MOFs晶体缺陷。以醇选择性氧化-Knoevenagel 缩合反应为串联催化模型反应，研究Zr-MOFs催化官能团和晶体缺陷协同催化机理，揭示多功能MOFs催化剂催化性能的构效关系。本项目研究将为开发高性能MOFs催化剂提供实验基础和理论依据。

本项目自实施以来，申请人围绕项目书中确立的研究目标和方法，以功能性金属-有机框架材料（MOFs）、共轭微孔聚合物（CMPs）和半导体薄膜材料的功能化为导向，已经按照计划完成了功能性多孔材料的设计、合成并开展了其在光电催化领域的应用。顺利完成了如下研究内容：（1）利用骨架侧链嫁接功能性有机配体策略，设计合成了30余种功能性有机配体；在此基础上，合成了出功能性MOFs 和CMPs异相催化剂，解决了小分子催化剂（如TEMPO自由基、苯并噻二唑）难以回收利用的难题，并系统研究了上述催化剂催化氧化各种有机分子官能团转化性能，开发出了对各种取代基芳香醇、硫醚具有高效催化氧化的MOFs和CMPs催化剂；（2）自主搭建了一套基于蠕动泵可控温全自动层层自组装系统，通过分步层层生长法（LBL）和自组装单层技术（SAMs）相结合的方法，建立了表面红外反射吸收光谱（IRRAS）研究MOFs表面自组装的新方法，解决了传统“一锅法”难以研究MOFs晶体生长的机理难题；（3）开发了功能性有机/无机半导体薄膜电化学合成方法，以水溶性苝四羧酸钾盐为原料，利用电化学氧化脱羧反应，在各类导电基底表面可控沉积苝聚合物薄膜，研究了光电催化苯甲醇性能。