Pumping between phases with a pulsed-fuel molecular ratchet.

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.

Rotary and linear molecular motors driven by pulses of a chemical fuel.

Many biomolecular motors catalyze the hydrolysis of chemical fuels, such as adenosine triphosphate, and use the energy released to direct motion through information ratchet mechanisms. Here we describe chemically-driven artificial rotary and linear molecular motors that operate through a fundamentally different type of mechanism. The directional rotation of [2]- and [3]catenane rotary molecular motors and the transport of substrates away from equilibrium by a linear molecular pump are induced by acid-base oscillations.