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Although a widely used and important industrial gas, ammonia (NH3) is also highly toxic and presents a substantial health and environmental hazard. The development of new materials for the effective capture and removal of ammonia is thus of significant interest. The capture of ammonia at ppm-level concentrations relies on strong interactions between the adsorbent and the gas, as demonstrated in a number of zeolites and metal-organic frameworks with Lewis acidic open metal sites. However, these adsorbents typically exhibit diminished capacity for ammonia in the presence of moisture due to competitive adsorption of water and/or reduced structural stability. In an effort to overcome these challenges, we are investigating the performance of porous polymers functionalized with Brønsted acidic groups, which should possess inherent structural stability and enhanced reactivity towards ammonia in the presence of moisture. Herein, we report the syntheses of six different Brønsted acidic porous polymers exhibiting -NH3Cl, -CO2H, -SO3H, and -PO3H2 groups and featuring two different network structures with respect to interpenetration. We further report the low- and high-pressure NH3 uptake in these materials, as determined under dry and humid conditions using gas adsorption and breakthrough measurements. Under dry conditions, it is possible to achieve NH3 capacities as high as 2 mmol g-1 at 0.05 mbar (50 ppm) equilibrium pressure, while breakthrough saturation capacities of greater than 7 mmol g-1 are attainable under humid conditions. Chemical and structural variations deduced from these measurements also revealed an important interplay between acidic group spatial arrangement and NH3 uptake, in particular that interpenetration can promote strong adsorption even for weaker Brønsted acidic functionalities. In situ infrared spectroscopy provided further insights into the mechanism of NH3 adsorption, revealing a proton transfer between ammonia and acidic sites as well as strong hydrogen bonding interactions in the case of the weaker carboxylic acid-functionalized polymer. These findings highlight that an increase of acidity or porosity does not necessarily correspond directly to increased NH3 capacity and advocate for the development of more fine-tuned design principles for efficient NH3 capture under a range of concentrations and conditions.

Metal-organic frameworks (MOFs) in their free powder form have exhibited superior capacities for many gases when compared to other materials, due to their tailorable functionality and high surface areas. Specifically, the MOF HKUST-1 binds small Lewis bases, such as ammonia, with its coordinatively unsaturated copper sites. We describe here the use of HKUST-1 in mixed-matrix membranes (MMMs) prepared from polyvinylidene difluoride (PVDF) for the removal of ammonia gas. These MMMs exhibit ammonia capacities similar to their hypothetical capacities based on the weight percent of HKUST-1 in each MMM. HKUST-1 in its powder form is unstable toward humid conditions; however, upon exposure to humid environments for prolonged periods of time, the HKUST-1 MMMs exhibit outstanding structural stability, and maintain their ammonia capacity. Overall, this study has achieved all of the critical and combined elements for real-world applications of MOFs: high MOF loadings, fully accessible MOF surfaces, enhanced MOF stabilization, recyclability, mechanical stability, and processability. This study is a critical step in advancing MOFs to a stable, usable, and enabling technology.

Metal–organic frameworks (MOFs) necessitate buffers or basic amine moieties for high activity and turnover in the hydrolysis of organophosphates. While polymeric amine buffers can be integrated with a MOF, all solid-state formulations suffer from active site poisoning of the secondary building units (SBUs) within MOFs which inhibits further catalytic turnover. Herein, we developed a simple soaking procedure with a basic aqueous solution that reactivates the active sites of spent MOFs after organophosphate catalysis. Moreover, we develop amine functionalized MOF-808 derivatives through de novo synthesis with H3-BTC-NH2 (BTC = 1,3,5-benzenetricarboxylic acid) and post-synthetic modification (PSM) that are highly active for organophosphate hydrolysis under non-buffered aqueous conditions. [ABSTRACT FROM AUTHOR]

Current approaches to create zirconium‐based metal–organic framework (MOF) fabric composites for catalysis, water purification, wound healing, gas sorption, and other applications often rely on toxic solvents, long reaction/post processing times, and batch methods hindering process scalability. Here, a novel mechanism was reported for rapid UiO‐66‐NH2 synthesis in common low‐boiling‐point solvents (water, ethanol, and acetic acid) and revealed acid–base chemistry promoting full linker dissolution and vapor‐based crystallization. The mechanism enabled scalable roll‐to‐roll production of mechanically resilient UiO‐66‐NH2 fabrics with superior chemical protective capability. Solvent choice and segregated spray delivery of organic linker and metal salt MOF precursor solutions allowed for rapid MOF nucleation on the fiber surface and decreased the energy and time needed for post‐processing, producing an activated composite in less than 165 min, far outpacing conventional MOF‐fabric synthesis approaches. The MOF‐fabric hydrolyzed and blocked permeation of the chemical warfare agent soman, outperforming the protection‐standard activated carbon cloth. This work presents both chemical insights into Zr‐MOF powder and fabric composite formation by a rapid, industrially relevant approach and demonstrates its practicality and affordability for high‐performing personal protective equipment. [ABSTRACT FROM AUTHOR]