Two Terbium Metal–Organic Frameworks Showing Fluorescence Sensing and Proton Conductivity

Two new terbium-based metal–organic frameworks, {[Tb(ADBA)(CH3COO)(H2O)]·H2O}n (MOF 1) and [Tb(ADBA)(HCOO)(DMF)]n (MOF 2) (H2ADBA = 4,4′-(9,10-anthracenediyl) benzoic acid), were synthesized by the solvothermal method. Structural analysis indicates that the TbIII ions in MOFs 1 and 2 are coordinated to acetic and formic acids, respectively, leading to differences in the structures. Fluorescence measurements show that both MOFs 1 and 2 are fluorescence sensors for Al3+ and Ga3+ with fluorescence enhancement and a blue shift. The detection limits of MOF 1 are 0.067 μM for Al3+ and 0.093 μM for Ga3+, and the detection limits of MOF 2 are 0.064 for Al3+ and 0.086 μM for Ga3+. The proton conductivity measurements of MOFs 1 and 2 indicate that the proton conductivities of MOFs 1 and 2 increase in resistance with increasing humidity. MOF 1 is more sensitive to humidity with a maximum conductivity of 1.07 × 10–5 S·cm–1 under 40 °C and 98% RH. Therefore, MOFs 1 and 2 are potential multifunctional MOF materials.