Recent advances in nanoarchitectures of monocrystalline coordination polymers through confined assembly

Various kinds of monocrystalline coordination polymers are available thanks to the rapid development of related synthetic strategies. The intrinsic properties of coordination polymers have been carefully investigated on the basis of the available monocrystalline samples. Regarding the great potential of coordination polymers in various fields, it becomes important to tailor the properties of coordination polymers to meet practical requirements, which sometimes cannot be achieved through molecular/crystal engineering. Nanoarchitectonics offer unique opportunities to manipulate the properties of materials through integration of the monocrystalline building blocks with other components. Recently, nanoarchitectonics has started to play a significant role in the field of coordination polymers. In this short review, we summarize recent advances in nanoarchitectures based on monocrystalline coordination polymers that are formed through confined assembly. We first discuss the crystallization of coordination polymer single crystals inside confined liquid networks or on substrates through assembly of nodes and ligands. Then, we discuss assembly of preformed coordination polymer single crystals inside confined liquid networks or on substrates. In each part, we discuss the properties of the coordination polymer single crystals as well as their performance in energy, environmental, and biomedical applications.

Cs sorption of Mn-Fe based Prussian blue analogs with periodic precipitation banding in agarose gel

We report the understanding of Cs sorption/desorption properties of Mn-Fe based Prussian blue analogs (Mn-Fe PBA) and Prussian blue (PB) in agarose gel via X-ray fluorescence spectroscopy and scanning electron microscopy. After contacting a 2 mass% agarose gel containing 100 mmol dm^-3 [Fe(CN)₆]^3- ions (inner electrolyte gel) with a 1 mass% agarose gel containing 550 mmol dm^-3 Mn²⁺ or Fe²⁺ ions (outer electrolyte gel) in a plastic straw for 11 days, the clipped 10 mm-long gel columns of uniformly formed precipitates (named "Mn-Fe PBA gel" and "PB gel") were used to investigate their Cs sorption/desorption properties. The Mn-Fe PBA gel showed several interesting features that were not observed in the PB gel. The Cs sorption capacity of the Mn-Fe PBA gel increased over time, and after ∼1200 h reached a value comparable to the most optimal values previously reported. During Cs sorption, Mn²⁺ ions were constantly released from the Mn-Fe PBA gel, and several periodic precipitation bands were generated. The positions of the periodic bands agreed with those of the peak distributions of Cs, Mn, and Fe, suggesting that the concentration fluctuation of Mn^II-Fe^III PBA in the gel resulted in the periodic band formation. In these bands, large crystallites (>10 μm) were dominant, suggesting the contribution of Ostwald ripening. During Cs desorption, while Mn²⁺ ions were released from the Mn-Fe PBA gel, the release of Cs⁺ ions was considerably suppressed (∼1/3 for the PB gel). Based on these results, a model for Cs sorption by the Mn-Fe PBA gel was proposed, and its potential applications were discussed.