Thermochemical Evidence for Strong Iodine Chemisorption by ZIF-8

Abstract

For the first time, using aqueous solution calorimetry, we clearly identify the chemisorption of an unusually strong iodine charge-transfer (CT) complex within the cages of a metal-organic framework. Specifically, we studied the sorption of iodine gas in zeolitic imidazolate framework-8 (ZIF-8, Zn(2-methylimidazolate)2). Two iodine-loaded ZIF-8 samples were examined. The first, before thermal treatment, contained 0.17 I2/Zn on the surface and 0.59 I2/Zn inside the cage. The second sample was thermally treated, leaving only cage-confined iodine, 0.59 I2/Zn. The energetics of iodine confinement per I2 (relative to solid I2) in ZIF-8 are ΔHads = -41.47 ± 2.03 kJ/(mol I2) within the cage and ΔHads = -18.06 ± 0.62 kJ/(mol I2) for surface-bound iodine. The cage-confined iodine exhibits a 3-fold increase in binding energy over CT complexes on various organic adsorbents, which show only moderate exothermic heats of binding, from -5 to -15 kJ/(mol I2). The ZIF-8 cage geometry allows each iodine atom to form two CT complexes between opposing 2-methylimidazolate linkers, creating the ideal binding site to maximize iodine retention.

Foldable interpenetrated metal-organic frameworks/carbon nanotubes thin film for lithium–sulfur batteries

“…To investigate the MOFs pore size effect on Li–S performance, HKUST-1 ((Cu 3 (BTC) 2 , cavity of 1.1 nm with 0.9 nm entrance and active copper sites; BTC: 1,3,5-benzenetricarboxlic acid)25, MOF-5 ((Zn 4 O(BDC) 3 , cavity of 1.5 nm with 0.8 nm entrance; BDC: benzene-1,4-dicarboxylic acid)26, and ZIF-8 ((Zn(mim) 2 , cavity of 1.16 nm with 0.34 nm entrance; mim: 2-Methylimidazole)27 based CNT composite thin films were prepared (Fig. 1, Supplementary Fig.…”

Thermally Robust 3-D Co-DpyDtolP-MOF with Hexagonally Oriented Micropores: Formation of Polyiodine Chains in a MOF Single Crystal

“…[102][103][104][105][106][107][108] Interestingly, when the robust solvent-free framework I was immersed into a solution of iodine in cyclohexane, its hexagonally-arranged channels allowed iodine to form very intriguing polyiodine chains. The iodine-captured framework of I, I_I 2 , was structurally characterized by X-ray crystallography ( Table 1).…”

Monitoring iodine adsorption onto zeolitic-imidazolate framework-8 film using a separated-electrode piezoelectric sensor

“…ZIF-8 is an excellent sorbent for molecular I 2 because of its suitable pore aperture size, large specific surface area, and high chemical and thermal stability [18,19]. With ZIF-8 film grown on PQC surface, the kinetic process of the adsorption I 2 vapor on the film was monitored by the SEPS.…”