A Fundamentally New Mode of Adsorption Makes its Debut

During the past 90 years, adsorption of molecules on surfaces and at interfaces has been investigated extensively in equilibrium systems with the focus on van der Waals interactions associated with physisorption and electronic interactions in the case of chemisorption. Now, a team of researchers in the Stoddart laboratory have demonstrated mechanisorption, which results from non-equilibrium pumping to form mechanical bonds between the adsorbent and the adsorbate. This active mode of adsorption has been realized on the surfaces of metal-organic frameworks grafted with arrays of molecular pumps. Adsorbates are transported from one well-defined compartment – the bulk – to another well-defined compartment – the interface – thereby creating large potential gradients in the form of chemical capacitors wherein energy is stored in metastable states. Mechanisorption extends, in a fundamental manner, the scope and potential of adsorption phenomena and offers a transformative approach to the control of chemistry at surfaces and interfaces. If we chemists can work out how mechanisorption can be incorporated into active structures, the storage of gases like hydrogen, carbon dioxide and methane will enter a whole new world and become a different ball game altogether. The challenge is essentially one of how do we create nanoconfinement away-from-equilibrium?

The research was published in the journal Science.

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