From a Collapse-Prone, Insulating Ni-MOF-74 Analogue to Crystalline, Porous, and Electrically Conducting PEDOT@MOF Composites

Electrically conductive porous metal-organic frameworks (MOFs) show great promise in helping advance electronics and clean energy technologies. However, large porosity usually hinders long-range charge transport, an essential criterion of electrical conductivity, underscoring the need for new strategies to combine these two opposing features and realize their diverse potentials. All previous strategies to boost the conductivity of porous MOFs by introducing redox-complementary guest molecules, conducting polymers, and metal nanoparticles have led to a significant loss of frameworks' porosity and surface areas, which could be otherwise exploited to capture additional guests in electrocatalysis and chemiresistive sensing applications. Herein, we demonstrate for the first time that the in situ oxidative polymerization of preloaded 3,4-ethylenedioxythiophene (EDOT) monomers into the polyethylenedioxythiophene (PEDOT) polymer inside the hexagonal cavities of an intrinsically insulating Ni-2(NDISA) MOF-74 analogue (NDISA = naphthalenediimide N,N-disalicylate), which easily collapses and becomes amorphous upon drying, simultaneously enhanced the crystallinity, porosity, and electrical conductivity of the resulting PEDOT@Ni-2(NDISA) composites. At lower PEDOT loading (similar to 22 wt %), not only did the Brunauer-Emmett-Teller surface area of the PEDOT@Ni-2(NDISA) composite (926 m(2)/g) more than double from that of evacuated pristine Ni-2(NDISA) (387 m(2)/g), but also its electrical conductivity (1.1 x 10(-5) S/cm) soared 10(5) times from that of the pristine MOF, demonstrating unprecedented dual benefits of our strategy. At higher PEDOT loading (>= 33 wt %), the electrical conductivity of Ni-2(NDISA)superset of PEDOT composites further increased modestly (10(-4) S/cm), but their porosity dropped precipitously as large amounts of PEDOT filled up the hexagonal MOF channels. Thus, our work presents a simple new strategy to simultaneously boost the structural stability, porosity, and electrical conductivity of intrinsically insulating and collapse-prone MOFs by introducing small amounts of conducting polymers that can not only reinforce the MOF scaffolds and prevent them from collapsing but also help create a much coveted non-native property by providing charge carriers and charge transport pathways.

Automated summary

In situ oxidative polymerization of preloaded EDOT monomers inside the hexagonal cavities of Ni-2(NDISA) MOF-74 analogue enhanced the crystallinity, porosity, and electrical conductivity of the resulting PEDOT@Ni-2(NDISA) composites, providing a new strategy to boost the properties of MOFs.