Department of Chemistry, University of Manchester, Manchester, UK.
School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, China.
Nat Nanotechnol. 2022 Jul;17(7):701-707. doi: 10.1038/s41565-022-01097-1. Epub 2022 Apr 4.
The sorption of species from a solution into and onto solids underpins the sequestering of waste and pollutants, precious metal recovery, heterogeneous catalysis, analysis and separation science, and other technologies. The transfer between phases tends to proceed spontaneously in the direction of equilibrium. For example, alkyl ammonium groups mounted on silica nanoparticles are used to chemisorb cucurbituril macrocycles from solution through host-guest binding. Molecular ratchet mechanisms, in which kinetic gating inhibits or accelerates particular steps, makes it possible to progressively drive dynamic systems away from equilibrium. Here we report on molecular pumps immobilized on polymer beads that use an energy ratchet mechanism to directionally transport substrates from solution onto the beads. On the addition of trichloroacetic acid (CClCOH) fuel, micrometre-diameter polystyrene beads functionalized with solvent-accessible molecular pumps sequester from the solution crown ethers appended with fluorescent tags. After fuel consumption, the rings are mechanically trapped in a higher-energy, out-of-equilibrium state on the beads and cannot be removed by dilution or exhaustive washing. This differs from dissipative assembled materials, which require a continuous supply of energy to persist, and from conventional host-guest complexes. The addition of a second fuel pulse causes the uptake of more macrocycles, which drives the system further away from equilibrium. The second macrocycle can be labelled with a different fluorescent tag, which confers sequence information on the absorbed structure. The polymer-bound substrates can be released back to the bulk either one compartment at a time or all at once. Non-equilibrium sorption by immobilized artificial molecular machines enables the transduction of energy from chemical fuels for the use, storage and release of energy and information.
物种从溶液中进入和吸附到固体中的吸附作用支撑着废物和污染物的隔离、贵金属回收、多相催化、分析和分离科学以及其他技术。相间的转移往往会自发地朝着平衡的方向进行。例如，负载在硅胶纳米粒子上的烷基铵基团通过主客体结合，从溶液中化学吸附葫芦脲大环。分子棘轮机制，其中动力学门控抑制或加速特定步骤，使得可以逐步使动态系统远离平衡。在这里，我们报告了固定在聚合物珠上的分子泵，它们使用能量棘轮机制将底物从溶液定向输送到珠上。在添加三氯乙酸（CClCOH）燃料后，功能化的具有溶剂可及性的分子泵的微米级聚苯乙烯珠从溶液中螯合带有荧光标记的冠醚。在燃料消耗后，这些环在珠上被机械捕获在更高能量的非平衡状态，并且不能通过稀释或彻底洗涤去除。这与需要连续供应能量才能持续存在的耗散组装材料以及传统的主客体复合物不同。添加第二个燃料脉冲会导致更多大环的吸收，从而使系统进一步远离平衡。第二个大环可以用不同的荧光标记标记，这为吸收的结构提供了序列信息。聚合物结合的底物可以一次一个隔室或全部释放回主体。固定化人工分子机器的非平衡吸附使化学燃料中的能量能够被转化为能量和信息的利用、储存和释放。
