Coordination-Driven Fluorescent J-Aggregates in a Perylenetetracarboxylate-Based MOF: Permanent Porosity and Proton Conductivity

Abstract

Here we report the synthesis and structural characterizations of a new 3D functional metal-organic framework {[K-8(PTC)(2)(H2O)(1.5)]center dot 4H(2)O}(n) formed by the self-assembly of K-I and chromophoric linker perylenetetra-carboxylate (PTC). The structure determination shows a 3D pillared-layer framework, where perylene cores are arranged in an unusual end-to-end off-slipped and zigzag arrangement directed by K-I-carboxylate bonding. Photophysical studies revealed a broad absorption band with lambda(max) of 531 nm and bathochromically shifted red emission centered at 655 nm. This characteristic emission has been assigned due to J-coupling of the PTC linkers in the solid state. The framework contains 1D water-filled channel, and the desolvated framework shows permanent porosity, "as realized by type-I CO2 adsorption profile at 195 K. Interestingly, the guest and coordinated water molecules in the framework are connected via H-bonding and based on these characteristics, the framework was further exploited for proton conduction. It shows remarkable conductivity of 1 x 10(-3) S cm(-1) under ambient conditions (98% RH) with low activation energy.