Separation processes are substantially more difficult when the species to be separated is highly dilute. To perform any dilute separation, thermodynamic and kinetic limitations must be overcome. Here we report a molten-carbonate membrane that can ‘pump’ CO₂ from a 400 ppm input stream (representative of air) to an output stream with a higher concentration of CO₂, by exploiting ambient energy in the form of a humidity difference. The substantial H₂O concentration difference across the membrane drives CO₂ permeation ‘uphill’ against its own concentration difference, analogous to active transport in biological membranes. The introduction of this H₂O concentration difference also results in a kinetic enhancement that boosts the CO₂ flux by an order of magnitude even as the CO₂ input stream concentration is decreased by three orders of magnitude from 50% to 400 ppm. Computational modelling shows that this enhancement is due to the H₂O-mediated formation of carriers within the molten salt that facilitate rapid CO₂ transport.

当待分离的物质高度稀释时，分离过程会变得更加困难。为了进行任何稀释分离，必须克服热力学和动力学限制。在这里，我们报道了一种熔融碳酸盐膜，它可以通过利用湿度差形式的环境能量，将 CO ₂从 400 ppm 输入流（代表空气）“泵”至具有更高浓度 CO ₂的输出流。膜上巨大的 H ₂ O 浓度差驱动 CO ₂相对于其自身的浓度差“上坡”渗透，类似于生物膜中的主动运输。这种H ₂ O浓度差的引入还导致动力学增强，即使CO ₂输入流浓度从50%降低到400 ppm三个数量级，CO ₂通量也提高了一个数量级。计算模型表明，这种增强是由于熔盐内 H ₂ O 介导的载体形成促进了 CO _{2 的}快速传输。