Functionalized Metal–Organic Frameworks for the Efficient Removal of Low Concentrations of Ammonia

Abstract

The excellent ammonia adsorption properties of [Cu(bpy)2(OTf)2]n (ELM‐12; bpy=4,4′‐bipyridine, OTf=trifluoromethanesulfonate) make it unique for the removal of ammonia at low concentrations, but its instability under humid conditions restrict its practical applications. Herein, a functionalized ELM‐12@PDMS (PDMS=polydimethylsiloxane) composite was prepared by coating a nanoscale PDMS layer on the ELM‐12 surface, which significantly increased its hydrophobicity. The dynamic ammonia adsorption properties of ELM‐12 and ELM‐12@PDMS were explored by means of kinetic breakthrough measurements under dry and humid conditions. ELM‐12@PDMS can effectively capture ammonia at 100 ppm when maintained under 80 % relative humidity, which makes it promising for real applications.

Reversible ammonia uptake at room temperature in a robust and tunable metal–organic framework

“…2b), which are comparable with other NH 3 adsorbing MOFs. 5–19,29 Notably, JCM-1 surpasses other materials in terms of framework stability upon regeneration, which are the critical properties of energy-efficient NH 3 adsorbent materials. Although a substantial number of MOFs were tested for ammonia adsorption thus far, they suffer from structural deformation after exposure to corrosive NH 3 gas.…”

“…Although a substantial number of MOFs were tested for ammonia adsorption thus far, they suffer from structural deformation after exposure to corrosive NH 3 gas. 5,7–19,39,41 Many of the MOFs show decreased porosity with the degradation of crystallinity during repeated NH 3 adsorption–desorption processes, resulting in peak broadening in powder X-ray diffraction (PXRD) patterns. In contrast, JCM-1 could maintain the initial crystallinity and the porosity after NH 3 adsorption experiments, which was confirmed by the almost unchanged PXRD patterns and N 2 sorption isotherms (Fig.…”

“…Metal–organic frameworks (MOFs) have emerged as a promising material for the capture of toxic chemicals such as NH 3 , 5–19 NO x , 20–23 SO x , 24–26 and volatile organic compounds 27,28 because well-ordered porosity with feasible chemical and structural tunability of pore surfaces enables such applications. Synthesis of MOFs with high structural stability toward corrosive species is a critical issue for real-world applications.…”

“…In this regard, several MOFs that can take up NH 3 under atmospheric condition has been developed recently. 5–19,29 Nevertheless, structural instability of adsorbent and high regeneration temperature are still remaining challenges for practical applications. 5,7–19 MOFs showing recyclable ammonia adsorption while retaining its porosity are still very rare.…”

“…5–19,29 Nevertheless, structural instability of adsorbent and high regeneration temperature are still remaining challenges for practical applications. 5,7–19 MOFs showing recyclable ammonia adsorption while retaining its porosity are still very rare. The limited stability of MOFs under ammonia conditions is ascribed to the coordinating nature of NH 3 .…”