Gallium Species Incorporated into MOF Structure: Insight into the Formation of a 3D Polycrystalline Gallium–Imidazole Framework

Abstract

The formation of a polycrystalline 3D gallium–imidazole framework (MOF) was closely studied in three steps using ssNMR, XRPD, and TGA. In all steps, the reaction products show relatively high temperature stability up to 500 °C. The final product was examined by structural analysis using NMR crystallography combined with TG and BET analyses, which enabled a detailed characterization of the polycrystalline MOF system on the atomic-resolution level. 71Ga ssNMR spectra provided valuable structural information on the coexistence of several distinct gallium species, including a tunable liquid phase. Moreover, using an NMR crystallography approach, two structurally asymmetric units of Ga­(Im6)6– incorporated into the thermally stable polycrystalline 3D matrix were identified. Prepared polycrystalline MOF material with polymorphic gallium species is promising for use in catalytic processes.

Construction of Polymers with Highly Dispersed Reactive Phases and Open Pores for Catalyzing the Efficient Synthesis of CO2 to α‐Methylene Cyclic Carbonates

“…The synthesized catalysts or precursors were analyzed for their chemical composition using characterization tools such as Solid State 13 C‐NMR, FT‐IR and XPS. The NMR spectra of homopolymer PII and copolymer CP‐PII are shown in Figure 1A and B, where the peaks of 120–150 ppm at the chemical shifts can be observed, and these peaks are on behalf of C atoms of imidazole or benzene structures [11] . Simultaneously, the characteristic peaks of 15–50 ppm are attributed to C atom peaks of methyl (−CH 3 ), methylene (−CH 2 −), and methyne (−CH−) produced by free‐radical polymerization in imidazolium iodide salt monomers [12] .…”

“…The NMR spectra of homopolymer PII and copolymer CP-PII are shown in Figure 1A and B, where the peaks of 120-150 ppm at the chemical shifts can be observed, and these peaks are on behalf of C atoms of imidazole or benzene structures. [11] Simultaneously, the characteristic peaks of 15-50 ppm are attributed to C atom peaks of methyl (À CH 3 ), methylene (À CH 2 À ), and methyne (À CHÀ ) produced by freeradical polymerization in imidazolium iodide salt monomers. [12] This tentatively confirms the formation of PII and CP-PII polymeric network structures.…”

“…The BrØnsted base species suitable for the carboxylative cyclization reaction were screened, and it was found that, except for DBU, no target product αCC was generated regardless of the addition of the organic bases TEA and DIEA or the inorganic bases Cs 2 CO 3 and K 2 CO 3 as the base additives (Table 1 Entry [7][8][9][10][11]. As shown in Table 1 Entry 12-14, the effect of BrØnsted base DBU dosage on the conversion of carboxylative cyclization reaction was studied.…”

Reconstructing Reliable Powder Patterns from Spikelets (Q)CPMG NMR Spectra: Simplification of UWNMR Crystallography Analysis

“…The computational procedure was followed, which was most recently successfully applied by some of us to the 71 Ga NMR parameters in reference [ 44 ], where further details can be found. In short, it applies the plane wave DFT-based calculations as implemented in the CASTEP 16.1 code [ 45 ] to first optimize the periodic structures of investigated crystals, and, subsequently, predict their NMR parameters by applying the GIPAW method [ 46 , 47 ].…”