六元氮杂环类MOF碳化制备氮掺杂有序微孔活性碳的规律及其性能研究

Metal organic frameworks (MOF) is now a hot research topic due to its high ordered structure and crystalline porous and has emerged as promising materials in the fields of gas storage, separation and catalysis. MOF is constructed from assembly of organic ligands with metal ions through coordination bond and its stability is less than carbon, therefore the carbonization using MOF or ZIF as precursor to prepare porous carbon has attracted more and more attentions. ZIF-derived porous carbons have showed efficient electrocatalysis for oxygen reduction reaction (ORR), which originates from the conjugation between the graphene π system and the nitrogen lone pair. Comparing to quintuple nitrogen containing heterocyclic compounds, in principle, hexahydroxy N- heterocyclic compounds should have more aromatic characteristics and much stronger catalytic activity. However, there is no any report in literature about carbonization using a MOF containing hexahydroxy N-heterocyclic ligands. In this research, a series of MOFs will be synthesized using hexahydroxy N-heterocyclic ligands and then a series of microporous carbons with highly ordered six-membered heterocyclic N-C structures will be prepared by carbonizing these MOFs. The transfer behaviours of ordered constructions and N-C structures in MOF to porous carbon during carbonization will be studied extensively. The natures of electrocatalysis and gas sorption for these novel N-doped carbons will also be studied. Doing this project will help us to understand the laws of MOF carbonization and at same time the new structures of MOFs and novel materials of N-doped carbon will be produced out.

MOF因其高度有序性和晶态多孔性而成为近年来的研究热点，在气体存储、分离及催化等方面具有很好的应用前景。但MOF是靠金属中心和配体以配位键的方式自组装而成，稳定性不如碳材料，所以用MOF或ZIF做前躯体进行碳化的研究引起了广泛关注。因为咪唑类五元氮杂环的芳香性π体系和氮原子孤对电子的协同效应，ZIF型碳显示出优良的电催化性能。从理论上讲，六元氮杂环的芳香性更强，与氮原子协同作用产生的催化效果应该更好。然而，由含六元氮杂环MOF碳化制备氮掺杂碳材料还未见公开报道。本申请拟用各种含六元氮杂环配体合成一系列MOF并进行碳化，制备出一系列新的具有六元N-C结构的有序微孔氮掺杂碳材料，研究MOF的有序性和N-C结构在碳化过程中的传导和移植规律，考察这些新型碳材料的电催化性能和气体吸附特性。该研究不仅能够构建新型MOF结构和新型氮掺杂碳材料，实现材料创新，而且在MOF碳化规律方面具有很强理论意义。

MOF材料作为一种有机无机杂化晶态多孔材料，具有结构均一、可设计性以及比表面积高、结构可调等优势，通过在高温下碳化，可得到一系列具有不同孔结构和功能基团的碳材料。由六元氮杂环MOF材料所具有的高度共轭性和芳香性带来的特性对所得的氮掺杂碳材料的影响尤为突出。在本研究中，重点研究了这类特定MOF在不同条件下碳化所得的碳材料的结构特征，考察了这类功能碳材料在气体吸附与分离、电催化氧还原、电催化析氢、析氧、二次电池电极材料、有机物催化加氢等领域的特性，探究碳材料的结构特性对特定应用的影响规律。研究结果表明：含有六元氮环结构的吡啶氮是二氧化碳的优先吸附位点，通过碳化含有吡啶氮的MOF材料可获得含有高密度吡啶氮的碳材料；MOF碳的六元环吡啶氮的含量、石墨化程度以及孔结构三者协同作用对氧还原（ORR）催化性能具有明显的提升作用；以MOF材料为前驱体，通过调控MOF材料的金属、形貌和碳化条件，可对碳材料的活性位点、电子结构、孔结构以及形貌进行人为调控，从而制备出高效的电催化析氢、析氧的非贵金属催化剂；利用MOF内金属离子高度分散的特点，通过一步碳化可获得高度分散的金属-碳复合材料，用于锂电、钠电、钾电等二次电池的电极材料、超级电容器的电极材料或有机物催化加氢的催化剂。除此之外，本研究在研究内容上还进行了扩展，开展微液滴法制备特殊形貌MOF材料的研究。在项目执行期内，在Advanced Functional Materials, Journal of Materials Chemistry A, Chemistry of Materials等国际期刊上发表了SCI研究论文23篇，其中SCI一区论文17篇，二区论文2篇，3篇论文被评为ESI高被引研究论文，顺利完成了预定的项目目标和任务。