A Multifunctional Co-Based Metal-Organic Framework as a Platform for Proton Conduction and Ni trophenols Reduction.

The design and development of proton conduction materials for clean energy-related applications is obviously important and highly desired but challenging. An ultrastable cobalt-based metal-organic framework Co-MOF , formulated as [Co 2 (btzip) 2 (μ 2 -OH 2 )] (namely, LCUH-103 , H 2 btzip = 4, 6-bis(triazol-1-yl)-isophthalic acid) had been successfully synthesized via the hydrothermal method. LCUH-103 exhibits a three-dimensional framework and a one-dimensional microporous channel structure with scu topology based on the binuclear metallic cluster {Co 2 }. LCUH-103 indicated excellent chemical and thermal stability; peculiarly, it can retain its entire framework in acid and alkali solutions with different pH values for 24 h. The excellent stability is a prerequisite for studying its proton conductivity, and its proton conductivity σ can reach up to 1.25 × 10 -3 S·cm - 1 at 80 °C and 100% relative humidity (RH). In order to enhance its proton conductivity, the proton-conducting material Im@ LCUH-103 had been prepared by encapsulating imidazole molecules into the channels of LCUH-103 . Im@ LCUH-103 indicated an excellent proton conductivity of 3.18 × 10 -2 S·cm - 1 at 80 °C and 100% RH, which is 1 order of magnitude higher than that of original LCUH-103 . The proton conduction mechanism was systematically studied by various detection means and theoretical calculations. Meanwhile, LCUH-103 is also an excellent carrier for palladium nanoparticles (Pd NPs) via a wetness impregnation strategy, and the nitrophenols (4/3/2-NP) reduction in aqueous solution by Pd@ LCUH-103 indicated an outstanding conversion efficiency, high rate constant ( k ), and exceptional cycling stability. Specifically, the k value of 4-NP reduction by Pd@ LCUH-103 is superior to many other reported catalysts, and its k value is as high as 1.34 min -1 and the cycling stability can reach up to 6 cycles. Notably, its turnover frequency (TOF) value is nearly 196.88 times more than that of Pd/C (wt 5%) in the reaction, indicating its excellent stability and catalytic activity.