Abstract
To develop promising adsorbent candidates for adsorptive denitrogenation, we screened the adsorption of NO, NO2, and NH3 in 19 M-HKUST-1 (M = Be, Fe, Ni, Cr, Co, Cu, V, Zn, Mo, Mn, W, Sn, Ti, Cd, Mg, Sc, Ca, Sr, and Ba) systematically using first-principle calculations. Of these, four variants of M-HKUST-1 (M = Ni, Co, V, and Sc) yield more negative adsorption Gibbs free energy ΔGads than the original Cu-HKUST-1 for three adsorbates, suggesting stronger adsorbate binding. Ti-HKUST-1, Sc-HKUST-1, and Be-HKUST-1 are predicted to have the largest NO, NO2, and NH3 adsorption energies within the screened M-HKUST-1 series, respectively. With the one exception of NO2 dissociation on V-HKUST-1, dissociative adsorption of NO, NO2, and NH3 molecules on the other considered M-HKUST-1 is energetically less favorable than molecular adsorption thermodynamically. The barrier calculations show that the dissociation is difficult to occur on Cu-HKUST-1 kinetically due to the very large dissociation barrier. Electronic analysis is provided to explain the bond nature between the adsorbates and M-HKUST-1. Note that the isostructural substitution of Cu to the other metals is a major simplification of the system, representing the ideal situation; however, the present study provides interesting targets for experimental synthesis and testing.
Highlights
To develop efficient denitrogenation techniques is extremely important due to the detrimental effects of nitrogen-containing compounds (NCCs) on the human health and environment [1,2].Among various denitrogenation techniques, adsorptive denitrogenation (ADN) is preferred because of its mild operating conditions
We focus on the adsorption performance of NCCs, including NO, NO2, and NH3, on M-HKUST-1 to investigate the effect of the metal center on the adsorption performance of NCCs on HKUST-1
We first performed a geometric optimization of the bulk structure of 19 M-HKUST-1
Summary
To develop efficient denitrogenation techniques is extremely important due to the detrimental effects of nitrogen-containing compounds (NCCs) on the human health and environment [1,2].Among various denitrogenation techniques, adsorptive denitrogenation (ADN) is preferred because of its mild operating conditions. Levasseur et al [14] prepared GO (graphite oxide) and HKUST-1 composites and conducted NO2 adsorption studies under dry and humid conditions. Their results showed that compared with a single adsorbent, only under dry conditions, the composite adsorbent increased the adsorption capacity of NO2 significantly. Borfecchia et al [15] studied the interaction of NH3 with HKUST-1 by a multitude of characterization techniques They found NH3 chemisorbed on the Cu site under the dry condition and induced the distortion framework, retained the crystallinity of the material [15]. According to previous research [8,12,13,14,15], it can be found that HKUST-1 exhibits excellent performance in adsorbing three kinds of NCCs (NO, NO2, and NH3) and preferentially adsorbed sites are the coordinatively unsaturated metal sites
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