Designing an efficient, stable and recyclable solid acid for catalytic conversion of biomass and its derived compounds to synthesize high value-added organic chemicals could effectively alleviate the environmental problems caused by the energy crisis and carbon dioxide emissions. We prepared a Keggin heteropolyacid modified macroporous covalent triazine frameworks (PW12-MCTF) catalyst using a simple template method and post-impregnation technology for efficient conversion of carbohydrates to produce 5-hydroxymethylfurfural (HMF). Abundant structural defects of MCTF can be constructed in situ through incomplete polymerization, which can firmly bind H3PW12O40 through physical confinement effect and bonding interactions. Under optimized conditions, PW12-MCTF exhibited high HMF yield (79.4 % or 44.4 %) and the highest turnover frequency (4.39 min−1 or 1.86 min−1) in microwave-assisted catalytic conversion of fructose or inulin, respectively. Its catalytic activity surpassed that of bulk PW12-CTF and commercial acid zeolite and resin catalysts, due to its appropriate acid properties, well-dispersed nature in DMSO, inter-connected pore structure and outstanding nucleophilic effect of N-rich units. Density Functional Theory (DFT) study provides a plausible mechanism in PW12-CTF-catalyzed fructose dehydration. The catalytic performance of PW12-MCTF remained unchanged after three cycles due to strong bonding interaction between the Keggin units and framework of MCTF. This study will provide a new strategy for the fabrication of heteropolyacid modified covalent organic frameworks with structural defects to achieve the high-value utilization of carbohydrates.

中文翻译：

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富含氰基缺陷的Keggin杂多酸修饰大孔共价三嗪骨架的制备用于碳水化合物的高值利用


设计一种高效、稳定、可回收的固体酸，用于催化转化生物质及其衍生化合物合成高附加值有机化学品，可以有效缓解能源危机和二氧化碳排放造成的环境问题。我们采用简单的模板法和后浸渍技术制备了Keggin杂多酸修饰的大孔共价三嗪骨架（PW12-MCTF）催化剂，用于高效转化碳水化合物生产5-羟甲基糠醛（HMF）。 MCTF可以通过不完全聚合原位构建丰富的结构缺陷，通过物理限域效应和键合相互作用牢固地结合H3PW12O40。在优化条件下，PW12-MCTF 在微波辅助催化转化果糖或菊粉中分别表现出高 HMF 产率（79.4 % 或 44.4 %）和最高周转频率（4.39 min−1 或 1.86 min−1）。由于其适当的酸性质、在DMSO中良好的分散性、互连的孔结构以及富氮单元突出的亲核效应，其催化活性超过了本体PW12-CTF和商业酸性沸石和树脂催化剂。密度泛函理论 (DFT) 研究提供了 PW12-CTF 催化果糖脱水的合理机制。由于 Keggin 单元和 MCTF 框架之间的强键合相互作用，PW12-MCTF 的催化性能在三个循环后保持不变。该研究将为制备具有结构缺陷的杂多酸修饰共价有机骨架以实现碳水化合物的高价值利用提供新策略。