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The search for new highly proton-conducting materials has been a subject of intense research because of their potential applications in fuel cells, sensors, and other areas. In recent years, metal–organic frameworks (MOFs) with well-defined pores have been investigated for this purpose because guest molecules, such as water and imidazole in the channels, and/or functional groups lining the channels can provide proton conduction pathways. However, to date, most MOFs do not show high proton conductivity, long-term stability, or durability in moisture. Similar to MOFs, in principle, are organic molecular porous materials, which may serve as good proton conductors, but their proton conduction behavior has never been investigated. We recently reported an organic molecular porous material based on cucurbit[6]uril (CB[6]), a member of the hollowed-out pumpkin-shaped macrocycle family cucurbit[n]uril (CB[n], n= 5–8, 10) having a hydrophobic cavity accessible through two polar carbonyl-laced portals. The organic molecular porous material has permanent porosity and high thermal and chemical stability, which makes it useful for gas storage and other applications. While investigating its crystal structure, we noticed that there is an array of water and acid molecules filling in the channels of the porous material, which prompted us to investigate the proton conductivity of this and related materials. Herein, we present the high and highly anisotropic proton conductivity in cucurbituril-based organic molecular porous materials, which can be modulated by the nature and amount of guest acid molecules present in the channels. Their proton conductivity along the channel direction, which was demonstrated by single-crystal conductivity measurements, is comparable or superior to that of most MOFs or organic proton conductors. To the best of our knowledge, this investigation of the proton conductivity in organic molecular porous materials with permanent porosity is unprecedented. Recrystallization of CB[6] from 2.4m HCl and 2.4m H2SO4 solutions produced the isostructural organic molecular porous materials CB[6]·1.1HCl·11.3H2O (1) and CB[6]·1.2H2SO4·6.4H2O (2), respectively. Single-crystal Xray analysis revealed that both 1 and 2 have a honeycomb-like structure with one-dimensional (1D) channels with an average diameter of 7.5 and an aperture of about 6 along the c axis (Figure 1a), which are filled with water and |
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