Iodine Adsorption in a Redox-Active Metal-Organic Framework: Electrical Conductivity Induced by Host-Guest Charge-Transfer.

Xinran Zhang,Alena M Sheveleva,Martin Schröder,Sihai Yang,Ivan Da Silva,Ming Li,Rodrigo Fazzi,Ben F Spencer,Floriana Tuna,Xue Han,Sergey A Sapchenko,Eric J L Mcinnes

doi:10.1021/acs.inorgchem.9b02176

Xinran Zhang, Alena M Sheveleva + Show 10 more

Open Access

https://doi.org/10.1021/acs.inorgchem.9b02176

Copy DOI

Abstract

We report a comparative study of the binding of I2 (iodine) in a pair of redox-active metal–organic framework (MOF) materials, MFM-300(VIII) and its oxidized, deprotonated analogue, MFM-300(VIV). Adsorption of I2 in MFM-300(VIII) triggers a host-to-guest charge-transfer, accompanied by a partial (∼30%) oxidation of the VIII centers in the host framework and formation of I3– species residing in the MOF channels. Importantly, this charge-transfer induces a significant enhancement in the electrical conductivity (Δσ = 700000) of I2@MFM-300(VIII/IV) in comparison to MFM-300(VIII). In contrast, no host–guest charge-transfer or apparent change in the conductivity was observed upon adsorption of I2 in MFM-300(VIV). High-resolution synchrotron X-ray diffraction of I2@MFM-300(VIII/IV) confirms the first example of self-aggregation of adsorbed iodine species (I2 and I3–) into infinite helical chains within a MOF.

Highlights

Nuclear energy shows promise to bridge future gaps in the supply of electricity.[1]
The binding of I2 in Metal−organic framework (MOF) with redox-active metal centers (e.g., FeII/III, CrII/III, VIII/IV, and NiII/III) remain largely unexplored, which can be attributed to the scarcity of reported stable redox-active MOFs.[12−15] collapse or, to a lesser extent, degradation of the MOF upon inclusion of I2 can occur, restricting the investigation of the host−guest binding via a charge-transfer mechanism
MFM-300(VIII), [V2(OH)2(L)] (H4L = biphenyl-3,3′,5,5′-tetracarboxylic acid), crystallizes in a tetragonal system in which the VIII center is coordinated by six O donors, four from carboxylates and two from bridging hydroxyl groups μ2-OH

Summary

■ INTRODUCTION

Nuclear energy shows promise to bridge future gaps in the supply of electricity.[1]. the radionuclides generated from the nuclear power plant can pose significant risks on both human health and ecosystems if emitted into the environment.[2]. IIII2 and IIV2 adopt low occupancies (0.16 and 0.10, respectively), reside in the center of the channel, and are stabilized by intermolecular interactions (Figure S10) These results confirm partial oxidation of the framework by adsorbed I2 molecules to afford a mixed-valence I2@MFM-300(VIII/IV) material. 1.901(2) 2.014(1) 2.070(9) 130.1(1) 3.447 3.278 detailed examination of [V2(O)2(L)]·2.2I2 confirmed that the confined I2 molecules within the pores aggregate to form an unusual helical chain running through the channel with a distance of 3.51(4) Å between adjacent I2 molecules × 10−10 S/cm, but I2@MFM-300(VIII/IV) shows a significant enhancement (Δσ = 700000) in conductivity in the dark to 1.2 × 10−4 S/cm (Figure S14) This can be attributed to both the oxidized V−O(H)−V skeletons and generated iodide chains that provide further transport pathways to facilitate electron transfer.[26] The value is comparable to the state-of-the-art conductivity observed I2@Cu[Ni(pdt)2]1 for. Bacipidh,eannydl-3H,4e′b,5ic-t=ric2a-rebtohxyyl-l1atHe,-bHe2n-z5o-t[bdi]pim=id5a-tzeorlte-b-5u-tcyalrisboopxhytlihcaaliccida.cibdF,iHlminsaw=eriesounseicdotfionricteasctiindg, Hof2-tDheL-elalecct=rilcaacltciconacdiudc,tHivpityyb. zcS=in4g-lpeycrriydsytlablesnwzeoriec used for testing of the electrical conductivity. dPressed pellets were used for testing of the electrical conductivity

■ CONCLUSION

■ ACKNOWLEDGMENTS

■ REFERENCES