Tröger’s Base Chemistry in Solution and in Zr(IV)-Based Metal–Organic Frameworks

Abstract

Troger's base (TB) and its derivatives have been studied extensively due to their unique concave shape stemming from the endomethylene strap. However, the strap-clipped TB chemistry has been largely overlooked in metal−organic framework (MOF) solids, leading to a gap in our knowledge within this field. In this work, we report the in situ strap elimination of a carboxylate-carrying TB in the presence of formic acid, both in solution and in Zr(IV)-based MOFs. In the solution system, the methanodiazocine nucleus can be exclusively transformed into an N,N′-diformyl-decorated phenhomazine derivative, regardless of the solvent used (DMF, DMA, or DEF), as unambiguously uncovered by single crystal X-ray crystallography. In contrast, while in the MOF synthetic system, the degree of derivatization reaction can be effectively controlled to give either the secondary diamine or formyl-decorated diamine, depending on the solvent used (DMF or DEF), resulting in the formation of two Zr-MOFs with 8connected bcu (NU-1900) and 12-connected fcu (NU-407) topologies, respectively. The derivatization mechanism is proposed to be topology-guided and dependent on the local acid concentration during the MOF formation processes. Moreover, we discovered a novel post-synthetically water-induced in situ linker formylation process in NU-1900 through sequential formic acid elimination, migration, and condensation processes, affording an isostructural framework with the same linker as in NU-407, which further corroborates our proposed mechanism. Additionally, the highly defective NU-1900 with abundant accessible Zr sites was demonstrated to be an outstanding catalyst for the detoxification of a nerve agent simulant with a half-life of less than 1 min.

Engineering of Stable Anionic/Neutral MOFs with Zinc-Adeninate Building Units for Efficient C2H2/CO2 Separation

“…Therefore, the scattering arising from the disordered solvent and Et 2 NH 2 was eliminated by utilizing the SQUEEZE subroutine of the PLATON software suite. Similarly, the free solvents in the crystal structure of 2 also were removed by the same method. , Thus, the final formulas are inconsistent with those in Table S1 generated after the SQUEEZE process during the structure refinement.…”

“…Based on the aforementioned considerations, (Et 2 NH 2 )­[Zn 3 (TCPE)­(adenine) 2 CH 3 COO]·DEF·3H 2 O ( 1 ), an anionic framework, was synthesized using Zn 2+ ions, adenine, and H 4 TCPE. By regulating the deprotonation and hydrolysis capacity of the solvent used for synthesis, , another neutral framework was obtained, [Zn 3.5 (adenine)­(TCPE) 1.5 (DMA)­(H 2 O) 0.5 ]·2DMA·2H 2 O ( 2 ) (Scheme ). Besides high stability, both MOFs contain high porosity, adsorption capacity for C 2 H 2 , and excellent C 2 H 2 /CO 2 selective separation performance.…”

Encapsulation of H4SiW12O40 into an Amide-Functionalized MOF: A Highly Efficient Nanocomposite Catalyst for Oxidative Desulfurization of Diesel Fuel

“…Metal–organic frameworks (MOFs) possess unique porosity, stability, and chemical and physical properties . This class of materials has been widely employed in a myriad of applications including the heterogeneous catalysis. − MOFs can be exploited as a solid catalyst in the ODS reactions due to their high density of active sites, various metal centers, adjustable pore shapes and sizes, high surface areas, and permanent porosities. , Furthermore, MOF pores can serve as individual “reactors” given their ability to host other catalytically significant molecules. , Although many MOF materials have been identified and synthesized, only a few studies have been devoted to the application of pristine MOFs as ODS catalysts. , Besides, the ODS catalytic behavior of MOFs could be enhanced through functionalization (especially by amide functional groups) and/or in combination with other catalytically active molecules (e.g., POMs) …”

Two Proton Conductive Coordination Polymers Constructed by an Unprecedented Structural Transformation of a Phosphine-Based Tricarboxylate Ligand

“…Studies have shown that the self-assembly of a metal ion and polycarboxylates with the assistance of an N-donor ligand is a very effective method . However, under specific reaction conditions, organic ligands may undergo unexpected transitions when interacting with metal centers, thus wonderfully tuning the physical properties of the complexes. − Such deformations of ligands are of great interest in coordination chemistry.…”