超/亚临界CO2体系中介孔g-C3N4基材料的低温液相制备及其多功能催化性研究

Visible-light photocatalysis is an effective method to solve the present serious problems of energy shortage and environmental deterioration. Graphitic carbon nitride (g-C3N4), as ideal visible-light-driven photocatalyst, has drawn great attention owing to its suitable band gap and band positions, high stability, and excellent performance in water splitting and degradation of organic pollutants. Unsatisfactorily, its photocatalytic efficiency is still restricted due to the high recombination rate of photogenerated electron-hole pairs and low surface area. Moreover, g-C3N4 is always synthesized by condensation of precursors at high temperature of 550°C, which to some extent results in the nitrogen depletion and kinetic problem. Additionally, in organic solvents, poor mass diffusion of organic precursors in the nanochannels of the templates and the competitive adsorption coming from H2O or other solvents in starting materials result in considerable textural structure defects of g-C3N4 material. To overcome these troubles existed in solid-state synthesis at high temperature and solvent solution-processed approach, in this project, we develop a novel synthesis avenue for mesoporous g-C3N4 and active materials dispersed g-C3N4 composites using templating method in super/subcritical CO2 at low temperature. Recently super/subcritical CO2 has become a potentially superior solvent for the synthesis and processing of nanomaterials due to its unique features of tunable physical properties characterized with low viscosity, high diffusivity and absence of surface tension. The photocatalytic performances of the mesoporous g-C3N4 and their composites are evaluated through degrading dyes and phenolic compounds under visible-light irradiation. Moreover, photocatalytic reduction of CO2 into renewable fuel or valuable chemicals is also investigated. Besides, the catalytic property over mesoporous g-C3N4 based composites is extended to the non-photocatalysis of CO2 conversion to cyclic carbonates. Based on the advanced characterization techniques combined with theoretical calculations, catalytic mechanisms for photocatalysis and non-photocatalysis processes are tentatively proposed, which in turn will direct the catalyst design.

光催化技术是解决能源短缺和环境恶化的有效手段之一，目前理想的可见光催化剂g-C3N4存在电荷分离效率差，比表面积低，其高温固相合成造成能耗高、氮流失，及液相合成存在的前驱体扩散差、溶剂竞争吸附等弊端,严重限制了g-C3N4材料广泛应用。针对这些问题，我们利用超/亚临界流体高扩散等特性，在超/亚临界CO2中采用模板法低温溶剂热合成各种形貌介孔g-C3N4及负载活性组分的复合物；以染料及难降解内分泌干扰物酚类为模型污染物来考察介孔g-C3N4及复合材料的光催化性能；CO2作为主要的温室气体也是丰富的C1资源，实现其资源化利用具有十分重要的经济和环境意义。我们将在超/亚临界CO2体系中制备的介孔g-C3N4基材料用于催化CO2转化利用，通过光催化和非光催化活化转化制清洁能源和有机化学品，拓展g-C3N4基材料的催化应用领域。通过现代表征并结合理论计算考察催化反应机理，为材料设计合成提供理论基础。

光催化技术是解决能源短缺和环境恶化的有效手段之一，目前理想的可见光催化剂g-C3N4存在电荷分离效率差，比表面积低等弊端,严重限制了g-C3N4材料广泛应用。二氧化碳是主要的温室气体，将CO2转化为增值的化学品引起了学术界和工业界的广泛关注。其中，利用环氧化物与CO2进行原子利用率为100%的环加成反应生产出环状碳酸酯是该领域最有前途的策略之一。项目负责人团队在多孔g-C3N4基催化材料设计合成及多功能性能方面如其光/电分解水和CO2,，对CO2的吸附及温和条件下热催化转化CO2合成高附加值的化学品的方面开展了一些具体的深入的研究工作，并将催化材料进一步拓展到MOF 基材料和离子液体材料。该项目的执行对于解决能源短缺，制备清洁能源及二氧化碳温室气体的减排和有效利用具有重要的科学意义。项目执行期间以通讯作者在Journal of Catalysis, Nano Energy, Catalysis Reviews, Chemical Engineering Journal, ACS Appl. Mater. Interfaces等高档次的期刊发表课题相关的SCI论文共37篇和1篇《科学通报》中文论文，其中2篇论文入选ESI前1％高被引论文，负责人孙建敏再次入选2018年英国皇家化学会RSC Top 1% 高被引中国学者，入选黑龙江省首批头雁团队计划。负责人及团队成员参加国内外学术会议6人次，负责人担任第一届全国二氧化碳资源化利用学术会议学术委员，在第一届全国二氧化碳资源化利用学术会议和 workshop on Green Synthesis and Catalysis Technology国际研讨会做邀请报告2次。项目期间共培养在读博士生11名，硕士生9名，毕业博士生2名，硕士生6人，1人获得哈工大优秀毕业论文金奖。