In situ synthesis of a MOFs/PAA hybrid with ultrahigh ionic current rectification.

In recent decades, the ionic current rectification (ICR) property of asymmetric nanochannels has been widely explored in applications of energy conversion, gas separation, water purification and bioanalysis/sensors. How to fabricate nanofluidic devices with a high ICR characteristic remains of critical importance to the development of nanofluidics. Herein, we fabricated an asymmetric MOFs/PAA hybrid via in situ synthesis of a zeolitic imidazole framework (ZIF-90) on porous anodic alumina (PAA) nanochannels. The introduction of asymmetric geometry and charge distribution provides the hybrid with ultrahigh ionic rectification, which can be easily measured using an electrochemical detector. This rectification mechanism is elucidated via finite element simulation, which proves that asymmetric geometry as well as the protonation and deprotonation under varied pH values dominates the ICR property. With the advantages of low cost and facile fabrication while supporting high ionic current rectification, the prepared MOFs/PAA hybrid can be considered as a significant paradigm in nanofluidic systems and has potential applications in the fields of new ionic devices and energy conversion systems.