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 {[K₈(PTC)₂(H₂O)_1.5]·4H₂O}_n formed by the self-assembly of K^I and chromophoric linker perylenetetracarboxylate (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 λ_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 × 10^-3 S cm^-1 under ambient conditions (98% RH) with low activation energy.