Multistep N₂ Breathing in the Metal−Organic Framework Co(1,4-benzenedipyrazolate)

Abstract

A variety of spectroscopic techniques combined with in situ pressure-controlled X-ray diffraction and molecular simulations have been utilized to characterize the five-step phase transition observed upon N(2) adsorption within the high-surface area metal-organic framework Co(BDP) (BDP(2-) = 1,4-benzenedipyrozolate). The computationally assisted structure determinations reveal structural changes involving the orientation of the benzene rings relative to the pyrazolate rings, the dihedral angles for the pyrazolate rings bound at the metal centers, and a change in the metal coordination geometry from square planar to tetrahedral. Variable-temperature magnetic susceptibility measurements and in situ infrared and UV-vis-NIR spectroscopic measurements provide strong corroborating evidence for the observed changes in structure. In addition, the results from in situ microcalorimetry measurements show that an additional heat of 2 kJ/mol is required for each of the first four transitions, while 7 kJ/mol is necessary for the last step involving the transformation of Co(II) from square planar to tetrahedral. Based on the enthalpy, a weak N(2) interaction with the open Co(II) coordination sites is proposed for the first four phases, which is supported by Monte Carlo simulations.

Host–Guest [2+2] Cycloaddition Reaction: Postsynthetic Modulation of CO2 Selectivity and Magnetic Properties in a Bimodal Metal–Organic Framework

“…2016, 22,7792 -7799 www.chemeurj.org nedipyrazolate) MOF (14.7 kJ mol À1 ), [10] but are comparable to the values observed in alkali metal ion exchange zeolites( 19-26 kJ mol À1 ). [11] Similart oM OF1 a, three binding sites also exist in MOF2 a. However,a fter PSM, the guest bpee molecules are bondedt ot he framework, and thus, both unsaturated Co II metal (UMS)s ites are inaccessible for CO 2 binding.…”

Uniaxial negative thermal expansion and metallophilicity in Cu3[Co(CN)6]

“…In this context, supramolecular interactions assume a particular importance, given that their energy scales are so much lower than those of electrostatic or covalent interactions. Hence the prevalence of hydrogen-bonding [9], halogenbonding [10], π -π [11], van der Waals (vdW) [5], host-guest [12,13], and metallophilic [14] interactions amongst many of the important materials in the field.…”

Structural Origin of Unusual CO2 Adsorption Behavior of a Small-Pore Aluminum Bisphosphonate MOF

“…Flexible MOFs show adsorption isotherms that sometimes deviate strongly from the standard convex shape of the expected I-type (at 77 K) or Langmuir-shaped (at room temperature) isotherm 17 and often exhibit inflection points 18 or steps. 19 We have previously made tremendous effort to understand the guest-induced flexible behavior of intermediate and large pore MOFs, [11][12][13][14]20,21 mostly based on polycarboxylate ligands. To complement this, we are currently investigating structural changes of small-pore-type MOFs with pore dimensions below 5 Å and the resulting effect on the adsorption of guest molecules with comparable size.…”