Stimulus-responsive proton conduction materials have attracted enormous interest as a new kind of “smart material”. It is desirable to develop the appropriate stimulus signal and high proton-conducting materials with an excellent proton-conducting switch ratio (γ), but it remains a great challenge. Here, it can be found for the first time that 4-((2-hydroxybenzylidene)amino)benzenesulfonic acid (HBABSA) has obvious thermal isomerization when porous solids act as matrixes at the ambient temperatures, which is different from that in the crystalline state at 77 K. Therefore, we proposed a host–guest metal–organic framework (MOF) composite, namely, MOF-808 incorporated with HBABSA (HBABSA@MOF-808), which has a proton-conducting switch ratio (γ) of 16 between 338 and 343 K due to the thermally induced isomerization of HBABSA molecules in the MOF pores. The strong binding between the keto-type HBABSA and MOF at the relatively low temperatures can efficiently suppress the proton conduction, while the enol-type one provides more mobile protons for conduction at the high temperatures due to the excited-state intramolecular proton transfer mechanism. Further, the HBABSA@MOF-808 as a filler is blended into polyvinyl alcohol and poly(2-acrylamide-2-methyl-1-propane sulfonic acid) to form hybrid membranes. The hybrid membrane with the highest content of the MOF composite displays a high proton conductivity of 5.57 × 10–3 S·cm–1 under 353 K and 57% RH along with a good switch ratio of 5.4. The development of thermal-response proton-conducting MOF materials is opening up a unique pathway for remote control, thermal sensing, intelligent batteries, and other fields.
Lu Zhou,Hao Fu,Zhe Wang,Ligang Chen,Guanhua Ren,Tao Jiang,Chenjie Gu,Liyuan Liu,Wentao Zhang,Weili Zhang,Jun Zhou,Jiaguang Han
Introducing novel nanomaterials into azobenzene (AB) and its derivatives enables a remarkable influence on the molecular isomerization and thus is of great interest for a variety of applications. We systematically study the thermal and photoinduced isomerization of p -aminoazobenzene ( p AAB) directly anchored on MoS 2 /GO nanocomposites by employing in-situ and real-time surface-enhanced Raman scattering (SERS) spectroscopy. The MoS 2 /GO nanocomposite provides the enhancements for the thermal isomerization efficiency of p AAB of more than 3-fold compared with that of the bare p AAB. We also show that the MoS 2 /GO nanocomposite has little impact on the UV-induced isomerization of the p AAB, but has apparent impact on the reverse cis -to- trans isomerization of the p AAB under blue light illumination. The results reveal that the effect of MoS 2 /GO nanocomposite on the photoinduced isomerization of p AAB depends on irradiation wavelength, which can be attributed to the competing interplay of charge transfer and structural relaxation in the hybrid system composed of p AAB and MoS 2 /GO nanocomposites. The study helps elucidate how the isomerization of azobenzene molecules is affected as incorporated into nanoscale assemblies, and thus open new opportunities for the applications of the isomerization of azobenzene in complex hybrid nanodevices.
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