Presence versus Proximity: The Role of Pendant Amines in the Catalytic Hydrolysis of a Nerve Agent Simulant

Abstract

Amino-functionalized zirconium-based metal-organic frameworks (MOFs) have shown unprecedented catalytic activity compared to non-functionalized analogues for hydrolysis of organophosphonate-based toxic chemicals. Importantly, the effect of the amino group on the catalytic activity is significantly higher in the case of UiO-66-NH , where the amino groups reside near the node, compared to UiO-67-m-NH , where they are directed away from the node. Herein, we show that the proximity of the amino group is crucial for fast catalytic activity towards hydrolysis of organophosphonate-based nerve agents. The generality of the observed amine-proximity-dictated catalytic activity has been tested on two different MOF systems which have different topology. DFT calculations reveal that amino groups on all the MOFs studied are not acting as Brønsted bases; instead they control the microsolvation environment at the Zr -node active site and therefore increase the overall catalytic rates.

Nylon–MOF Composites through Postsynthetic Polymerization

“…[1] Thel arge,o pen cavities form an interconnected porous network, and consequently, MOFs display exceptional sorption capacities across ab road range of applications.T his property of MOFs,c oupled with catalytic activity derived from functional units on the ligands and active metal sites at the SBU,have attracted great interest as functional porous materials. [2] Fore xample,Z r 4+ -based MOFs have been investigated as sorbents that can also catalytically degrade chemical warfare agents (CWAs); [3] however, few examples have demonstrated this activity in afunctional form factor. [4] Assembly of composite materials with MOFs has proven to be an effective way to exploit the desired properties of MOFs,such as porosity and catalytic activity,inaform factor that makes their handling and implementation considerably easier than in the native,p owder form.…”

Microwave-Assisted Solvothermal Synthesis of UiO-66-NH2 and Its Catalytic Performance toward the Hydrolysis of a Nerve Agent Simulant

“…This difference is mainly due to the different sizes of MOF catalyst particles and the introduction of different defects. However, these two factors are often intertwined with each It is worth mentioning that there have been several reports concerning the degradation properties of UiO-66-NH 2 powders [19,[25][26][27][28][29][30]. The shortest half-life of degradation of DMNP catalyzed by UiO-66-NH 2 reported in the literature is less than 1 min [26] while the longest half-life reaches 495 min [19].…”

Recent Advances of MOFs and MOF‐Derived Materials in Thermally Driven Organic Transformations

“…DFT calculations revealed that the position of the amino group on the 1,4-benzene dicarboxylate struts influence the microsolvation environment of the active sites on the Zr 6 -SBU, ap henomenon that alters the reaction rate. [27] Cui et al also found that the hydrophobic tert-butyl groups on the ligand found in MOF 1-Cr/Mg/Mn, not only protects the vulnerable M-O coordination bonds improving MOF stabilityu nder harsh conditions, but also exerts steric limitations and further Figure 3. Isoindoline nitroxide radical was anchored onto the ligand to syn-thesizeaCu-MOF,knowna s[ Cu(DPIO) 2 (SiF 6 )],w hich was used for the selective oxidation of alcohols to aldehydes or ketones.…”

“…reported that UiO‐66‐NH 2 with the amino group in the ortho position of the linker showed better catalytic performance in the hydrolysis of a organophosphonate‐based nerve agent, dimethyl 4‐nitrophenyl phosphate (DMNP), than a UiO‐66‐NH 2 analog with the amino group in the meta position. DFT calculations revealed that the position of the amino group on the 1,4‐benzene dicarboxylate struts influence the microsolvation environment of the active sites on the Zr 6 ‐SBU, a phenomenon that alters the reaction rate . Cui et al.…”