Bimetallic nickel complexes for selective CO₂ carbon capture and sequestration

Abstract

Herein we report a dinickel azacryptand complex that enables fast, selective, and tight CO2 binding from air. Exploiting the affinity of the cavitand towards azides, CO2 release was observed. Despite the stability of the azido complex, UV irradiation under atmospheric conditions proved to be a suitable pathway for N3(-) replacement by CO2.

Modulation of the CO2 fixation in dinickel azacryptands

“…, L A OMe and L A Me ) showed absorption bands at ∼390, 480, 560, and 620 nm, the spectra of shared structural motif of the above-mentioned complexes. 23 Likewise, ESI-MS experiments support a similar composition of the compounds by showing comparable mass patterns (Fig. S6 †).…”

“…Both Ni 2+ centers were found to be in the highspin state (S = 1) consistent with the observed octahedral and trigonal-bipyramidal coordinations of the Ni 2+ centers and this finding is in line with previous SQUID measurements. 23 The two triplet states were found to be exchange-uncoupled by broken-symmetry calculations. Though the substituents differ in their electron-donating and withdrawing capacities, no electronic effect was observed at the nickel ions as well as at all amines, as became apparent from unchanged Mulliken charges, bond distances and orbital compositions.…”

“…Å). 23,33 The general coordination of azides within the cavity and the alteration of the Ni-Ni distances within structurally comparable metal complexes underline the influence of the substitution pattern. It also shows that CO 2 is a key component in the different uptake kinetics.…”

“…The azacryptands L A R were synthesized via a two-step synthesis according to literature procedures (Scheme 1). 9,19,20,[23][24][25][26] In a first step, [ (ClO 4 ) 2 in 33% yield by a Ni-catalyzed imine hydrolysis in the presence of water of crystallization (Scheme 2). 27 The molecular structure was unequivocally confirmed by X-ray crystallography ( Fig.…”

“…Structural analysis revealed that one of the two Ni(II)-centers is coordinated by a water molecule and an acetonitrile, while the other is coordinated to a chloride. 23…”