Huang Pengcheng, Yan Yu, Martinho Ricardo P, Lefferts Leon, Wang Bin, Faria Albanese Jimmy
Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical Engineering, Changzhou University, Changzhou 213164, PR China.
School of Chemical, Biological and Materials Engineering, University of Oklahoma, Norman, Oklahoma 73019, United States.
JACS Au. 2024 Jun 28;4(7):2656-2665. doi: 10.1021/jacsau.4c00389. eCollection 2024 Jul 22.
Enzymes can precisely control the speed and selectivity of chemical reactions by modifying locally the solvent-reactant interactions. To extrapolate these attributes to heterogeneous catalysts, we have employed thermoresponsive poly -isopropylacrylamide (-NIPAM) brushes bonded to silica spheres containing palladium. These polymers can form hydrogen bonds with water molecules at low temperatures (<32 °C) allowing the polymer to stay swollen. Detailed reaction kinetics of nitrite hydrogenation showed that -NIPAM decreases the apparent activation barrier by a factor of 3 at low temperatures. Diffusion-ordered spectroscopy nuclear magnetic resonance and ab initio molecular dynamics simulations showed that when -NIPAM is present, water molecules near the surface are less mobile. This confinement perturbs the water interaction with the metal, reducing the barrier for the proton-electron transfer reduction of nitrite. Notably, this enhancement vanishes at high temperature as the polymer collapses on itself exposing the Pd to unconfined water. The fully reversible nature of this process opens the door for creating homeostatic catalysts with controlled water-confinement.
酶可以通过局部改变溶剂与反应物之间的相互作用来精确控制化学反应的速度和选择性。为了将这些特性外推到多相催化剂上，我们使用了键合到含钯二氧化硅球上的热响应性聚异丙基丙烯酰胺（-NIPAM）刷。这些聚合物在低温（<32°C）下可与水分子形成氢键，使聚合物保持溶胀状态。亚硝酸盐加氢的详细反应动力学表明，-NIPAM在低温下将表观活化能垒降低了3倍。扩散有序光谱核磁共振和从头算分子动力学模拟表明，当存在-NIPAM时，表面附近的水分子流动性降低。这种限制扰乱了水与金属的相互作用，降低了亚硝酸盐质子-电子转移还原的能垒。值得注意的是，随着聚合物自身塌陷，使钯暴露于无限制的水中，这种增强作用在高温下消失。该过程的完全可逆性为创建具有可控水限制的稳态催化剂打开了大门。
