Modulating the electrical conductivity of metal–organic framework films with intercalated guest π-systems

Abstract

The access to electroactive metal–organic frameworks (MOFs) and the ability to manipulate their electrical properties with external stimuli are vital for the realization of MOF-based electronic and photonic devices. To this end, we have constructed a new blue colored pillared-paddlewheel (PPW) MOF, namely BMOF composed of redox-active N,N′-bis(4-pyridyl)-2,6-dipyrrolidyl naphthalenediimide (BPDPNDI) pillars and 1,2,4,5-tetrakis-(4-carboxyphenyl)benzene (TCPB) struts, and grown stable, uniform BMOF films on ZnO substrates via a bottom-up method for device integration and testing. The electrical conductivity (σ) of BMOF films is ca. 6 × 10⁻⁵ S m⁻¹ (25 °C), which surges up to 2.3 × 10⁻³ S m⁻¹ upon infiltration of π-acidic methyl viologen (MV²⁺) guests, but remains unaffected by large C₆₀ molecules that are size excluded. These results demonstrate for the first time that the conductivity of MOFs can be fine-tuned by complementary guest π-systems that can promote long-range electron delocalization by forming extended π-stacks with the redox-active ligands.