Multifunctional Cd(II) Metal-Organic Framework with Abundant Lewis Acidic and Basic Sites: Selective Gas Adsorption and Separation, CO2 Catalytic Fixation, and Fluorescence Recognition of Uric Acid.

The development of new porous materials for the selective adsorption and fixation of CO2, as well as the selective capture of C2H2, is essential for environmental protection and energy security. Herein, a versatile coordination polymer, {[Cd(btbpa)(H2O)]·3H2O·4NMP·DMA}n (Cd-btbpa, H2btbpa = 4,4'-bis(1H-1,2,4-triazole-1-yl)-[1,1'-biphenyl]-3,3'-dicarboxylic acid), has been prepared, which not only exhibits good chemical and thermal stability but also possesses adaptive nanochannels. Gas uptake studies disclosed the selective adsorption properties of MOF Cd-btbpa for CO2 and C2H2 over other gases (N2, CH4, C2H4, and C2H6), contributing to a record-high IAST selectivity of ca. 3905 (50/50 of CO2/CH4, v/v). The adsorption selectivity values for C2H2/C2H4 and CO2/N2 at 298 K are 2.14 and 41.79, respectively. Breakthrough experiments were carried out to confirm its practical application value for CO2/CH4, CO2/N2, and C2H2/C2H4 separation. In addition, it can drive heterogeneous cycloaddition of CO2 with various epoxides under mild conditions (75 °C, 1 atm) and boost the yield of produced cyclic carbonates almost to 100% for the epoxides such as 1,2-epoxybutane and epichlorohydrin. Besides, Cd-btbpa shows excellent recognition ability for uric acid (UA) with high KSV (3.9378 × 104 M-1) and sensitivity (LOD: 0.14 μM).