Let Sumanta, K Dam Gourab, Fajal Sahel, Ghosh Sujit K
Department of Chemistry, Indian Institute of Science Education and Research Dr Homi Bhabha Road, Pashan Pune 411008 India
Centre for Water Research, Indian Institute of Science Education and Research Dr Homi Bhabha Road, Pashan Pune 411008 India.
Chem Sci. 2023 Sep 7;14(38):10591-10601. doi: 10.1039/d3sc03525e. eCollection 2023 Oct 4.
One-pot cascade catalytic reactions easily allow the circumvention of pitfalls of traditional catalytic reactions, such as multi-step syntheses, longer duration, waste generation, and high operational cost. Despite advances in this area, the facile assimilation of chemically antagonistic bifunctional sites in close proximity inside a well-defined scaffold a process of rational structural design still remains a challenge. Herein, we report the successful fusion of incompatible acid-base active sites in an ionic porous organic polymer (iPOP), 120-MI@OH, a simple ion-exchange strategy. The fabricated polymer catalyst, 120-MI@OH, performed exceedingly well as a cascade acid-base catalyst in a deacetylation-Knoevenagel condensation reaction under mild and eco-friendly continuous flow conditions. In addition, the abundance of spatially isolated distinct acidic (imidazolium cations) and basic (hydroxide anions) catalytic sites give 120-MI@OH its excellent solid acid and base catalytic properties. To demonstrate the practical relevance of 120-MI@OH, stable millimeter-sized spherical composite polymer bead microstructures were synthesized and utilized in one-pot cascade catalysis under continuous flow, thus illustrating promising catalytic activity. Additionally, the heterogeneous polymer catalyst displayed good recyclability, scalability, as well as ease of fabrication. The superior catalytic activity of 120-MI@OH can be rationalized by its unique structure that reconciles close proximity of antagonistic catalytic sites that are sufficiently isolated in space.
一锅法级联催化反应能够轻松规避传统催化反应的诸多缺陷，如多步合成、反应时间长、产生废物以及操作成本高等问题。尽管该领域已取得进展，但在一个明确的支架结构内将化学性质相互拮抗的双功能位点轻松融合——这一合理的结构设计过程仍然是一项挑战。在此，我们报道了通过一种简单的离子交换策略，成功地将不相容的酸碱活性位点融合在离子型多孔有机聚合物（iPOP）120-MI@OH中。所制备的聚合物催化剂120-MI@OH在温和且环保的连续流动条件下，作为级联酸碱催化剂在脱乙酰化-克诺文纳格尔缩合反应中表现出色。此外，大量空间隔离的不同酸性（咪唑鎓阳离子）和碱性（氢氧根阴离子）催化位点赋予了120-MI@OH优异的固体酸碱催化性能。为了证明120-MI@OH的实际应用价值，合成了稳定的毫米级球形复合聚合物微珠结构，并将其用于连续流动条件下的一锅级联催化反应，从而展现出良好的催化活性。此外，这种多相聚合物催化剂还具有良好的可回收性、可扩展性以及易于制备的特点。120-MI@OH卓越的催化活性可归因于其独特的结构，该结构使相互拮抗的催化位点在空间上充分隔离的同时又紧密相邻。
