Adsorption of Lower Alkanes on a Zinc Based Metal Organic Framework

Abstract

In this work, we report the gas adsorption properties of C2H6, C3H8, i-C4H10, and n-C5H12 on Zn2(bdc)2(dabco)(H2O)0.5(DMF)4 commonly known as ZnDABCO metal organic framework (MOF). Gravimetric adsorption measurements were performed at three different temperatures (294, 314, and 350 K) and a wide pressure range. For the linear alkanes, the isotherms were of Type-I; however, i-C4H10 exhibits a Type-IV isotherm at 294 K. Adsorption capacities on ZnDABCO are found to be higher than that on convention adsorbents like activated carbons and silicalites. The isotherms for linear alkanes were fit to a modified virial model. Enthalpy of adsorption was calculated using model parameters; it increases with loading indicating the role of lateral interactions. As is to be expected, a linear correlation was observed between the polarizability of the adsorbates and the enthalpy at zero loading (vertical interactions).

Hydrocarbon Separations in Metal–Organic Frameworks

“…The strength of adsorption between longer alkanes and the surfaces of metal–organic frameworks is generally correlated with the potential for van der Waals interactions. Accordingly, the reported strengths of adsorption followed the order n -pentane > propane > butane in Zn 2 (bdc) 2 (dabco) (dabco =1,4-diazabicyclo[2.2.2]octane), which has a structure in which two-dimensional sheets of bdc 2– -linked zinc-paddlewheel units are pillared by dabco . This trend can presumably explain the behavior of an analogous framework, Zn 2 (bdc) 2 (bpy) (bpy =4,4′-bipyridine), which can separate n -pentane from n -hexane .…”

“…Accordingly, the reported strengths of adsorption followed the order npentane > propane > butane in Zn 2 (bdc) 2 (dabco) (dabco =1,4diazabicyclo[2.2.2]octane), which has a structure in which twodimensional sheets of bdc 2− -linked zinc-paddlewheel units are pillared by dabco. 60 This trend can presumably explain the behavior of an analogous framework, Zn 2 (bdc) 2 (bpy) (bpy =4,4′-bipyridine), which can separate n-pentane from nhexane. 61 Similarly, a porphyrin-linked covalent polymer, PCPF-1, demonstrates linearly increasing adsorption capacities for C5−C8 linear hydrocarbons.…”

Efficient Mechanochemical Synthesis of MOF-5 for Linear Alkanes Adsorption

“…Therefore, the efficient separation of linear alkanes is of great significance in the petrochemical industries . Currently, adsorption is a cost-effective and highly efficient energy technique for alkanes separation. , An adsorbent is the key of adsorption technology. Thus, extensive efforts have been made to develop new adsorbents with superior linear alkanes separation.…”

Adsorption and Separation of Carbon Dioxide Using MIL-53(Al) Metal-Organic Framework

“…have been widely investigated for adsorption and separation of CO 2 . In addition, over the past decade, a new class of porous adsorbent commonly known as metal-organic frameworks (MOFs) has been widely synthesized and investigated by several researchers for CO 2 capture and separation applications. − …”