New Pillar-MOF with Nitrogen-Donor Sites for CO2 Adsorption

Abstract

A new pillar-MOF [Zn-2(L)(DABCO)] was solvothermally synthesized by using a new linker (L = 4,4 ‘-(1,4-phenylenebis(3,5-dimethyl-1H-pyrazole-4,1-diyl))dibenzoic acid), Zn(NO3)(2)6H(2)O, and triethylenediamine (DABCO) as pillar linker. It was characterized using single-crystal X-ray diffraction, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) and tested for CO2 adsorption. It exhibits dinuclear paddle-wheel nodes where the Zn(II) cations are coordinated by four equatorial L linkers generating two-dimensional sheets. DABCO acted as a pillar binding the sheets to obtain a neutral three-dimensional framework that shows one-dimensional square channels. The new pillar-layered MOF presents micro- and mesopores, and its crystallinity is preserved after activation at 160 degrees C x 16 h and adsorption of CO2. Due to the presence of the pyrazole nitrogen atoms in the framework, which have an increased affinity toward CO2, this new material exhibited a reasonable CO2 uptake capacity and a low isosteric enthalpy of adsorption (H-ads).