A Porous Polymer-Based Solid Acid Catalyst with Excellent Amphiphilicity: An Active and Environmentally Friendly Catalyst for the Hydration of Alkynes

Abstract

Developing efficient solid acid catalysts for aqueous organic reactions is of great importance for the development of sustainable chemistry. In this work, a porous polymeric acid catalyst was synthesized via a solvothermal copolymerization and a successive ion-exchange method. Physicochemical characterizations suggested that the prepared polymers possessed large Brunauer-Emmett-Teller (BET) surface areas, a hierarchically porous structure, excellent surface amphiphilicity, and nice swelling properties. Notably, an activity test in phenylacetylene hydration indicated that the prepared solid acid exhibited high catalytic activity in water, which outperformed commercial amberlyst-15, sulfuric acid, and benzenesulfonic acid. Moreover, the prepared solid acid can be easily recovered and reused at least four times. Additionally, a variety of aromatic and aliphatic alkynes could be effectively transformed into corresponding ketones under optimal reaction conditions. Porous organic polymers (POPs), which feature designable chemical functionalities and large surface areas, have recently received great research interest in the field of catalysis, due to their potential to combine the advantages of heterogeneous and homogeneous catalysis [22][23][24][25]. To date, a considerable number of porous polymeric acids have been successfully developed for various acid-catalyzed reactions [26][27][28]. Generally, for solid catalysts in water, the catalysts should be designed to be amphiphilic, thus allowing the nice contact between organic substrates, water, and the solid catalyst [29][30][31]. However, most porous polymeric acids are mainly composed of aromatic frameworks, endowing the catalyst with hydrophobic surface wettability [26,27,32], and thus, restricting their catalytic applications in water. Porous ionic polymers (PiPs) [33,34], which represent a new kind of porous organic polymer (POP) [33][34][35], could be easily prepared from the free radical polymerization of vinyl-functionalized organic salts. When used as the catalytic supports, PiPs can exhibit not only the features of POPs, but also some additional advantages, such as allowing easy functionalization via ion-exchange reactions and easy adjustment of surface wettability of the polymer [35][36][37][38].To develop an efficient and solid acid catalyst for the hydration of alkynes in water, herein, we initiate the synthesis of amphiphilic porous polymeric acids containing both the sulfonic and phosphonium salt groups (P(QPOTf-BSA)) and study their catalytic performances in water-mediated alkyne hydration. The amphiphilic and hyper-cross-linked P(QPOTf-BSA) was facilely synthesized through the free-radical copolymerization of 4-vinylbenzyl-tris-(4-vinylphenyl)-phosphonium chloride (QP) and sodium p-styrene sulfonate, followed by ion-exchange with HSO 3 CF 3 , as shown in Scheme 1. An activity test in phenylacetylene hydration suggested that the obtained P(QPOTf-BSA) exhibited excellent activity, outperforming the activities of heterogeneous amberlyst-15, as well as hom...

Iron–Organic Framework Nanoparticle-Supported Tungstosilicic Acid as a Catalyst for the Biginelli Reaction

“…However, these traditional catalysts suffer from a low yield, nonrecoverability of the catalyst, a long reaction time, and rigorous reaction conditions. To address the shortcoming, various catalysts have been developed, including ion-exchange resins, ionic liquids, solid-phase reagents, magnetic catalysts, SO 3 H-functionalized porous organic polymer, , and others . However, a good deal of these catalytic methodologies involves the use of a tedious work-up procedure, incompatibility with other functional groups, the use of expensive reagents, and environmental hazards .…”

Mesoporous Crystalline Niobium Oxide with a High Surface Area: A Solid Acid Catalyst for Alkyne Hydration

“…Conventionally, this reaction is carried out in the presence of a large number of acidic reagents and highly toxic additives such as mercury­(II) salts and mercury­(II) oxide. , Hence, several homogeneous catalysts have been developed to replace these toxic reagents. − Although these catalysts efficiently convert various alkynes to the corresponding ketones, they suffer from several drawbacks including the use of high-cost noble metals, requirement of additives such as ligands, and problems in separation and reusability of the catalyst. To overcome these issues heterogeneous catalysts including graphene oxide, tin–tungsten mixed oxide, Au-NHC@porous organic polymers, silver-exchanged silicotungstic acid catalyst, polymer-based solid acids, Hβ zeolites, , and poly­(ionic liquid)­s solid acids have been developed recently. Some of these catalysts such as tin–tungsten mixed oxide have shown excellent catalytic activities toward alkyne hydration.…”