NH3 is the most important gaseous alkaline pollutant,
which when accumulated at high concentrations can have a serious impact
on animal and human health. More importantly, NH3 emissions
will react with acidic pollutant gases to form particulate matter
(PM2.5) in the atmosphere, which also poses a huge threat
to human activities. The use of adsorbents for NH3 removal
from emission sources or air is an urgent issue. However, there are
difficulties in the compatibility between high adsorption capacity
and recyclability for most conventional adsorbents. In this work,
a structural transformation strategy using metal–organic frameworks
(MOFs) is proposed for large-scale and recyclable NH3 adsorption.
A series of M(BDC) (M = Cu, Zn, Cd) materials can transform into one-dimensional
M(BDC)(NH3)2 after NH3 adsorption,
resulting in repeatable adsorption capacities of 17.2, 14.1, and 7.4
mmol/g, respectively. These MOFs can be completely regenerated at
250 °C for 80 min with no adsorption capacity loss. Besides,
breakthrough and cycle tests indicate that Cu(BDC) and Zn(BDC) show
good performance in the removal of low concentrations of NH3 from the air. Overall, combining the advantages of high adsorption
capacity and recyclability due to the reversible structural transformation,
Cu(BDC) and Zn(BDC) can be employed as ideal adsorbent candidates
for NH3 removal.
Acetylene, an important petrochemical feedstock, is the starting chemical to produce many polymer products. Separating C2H2 from its by‐product mixtures is still an energy‐consuming process and remains challenging. Here, we present a metal–organic framework[Zn2(bpy)(btec)], with a desirable pore geometry and stable framework, which demonstrated a high separation performance of C2H2 from simulated mixtures. With the desirable pore dimension and hydrogen bonding sites, Zn2(bpy)(btec) shows by far the both highest C2H2/C2H4 and C2H2/CO2 uptake ratios, very high adsorption selectivities and moderately C2H2 uptake of 93.5 cm3/cm3 under 298 K and 1 atm. Not only straightforwardly produced high purity of C2H4, but also recovered high purity of C2H2 (>98%) in the regeneration process (>92% recovery). More notably, Zn2(bpy)(btec) can be straightforwardly synthesized at a large scale under environmentally friendly conditions, and its good water/chemical stability, thermostability, and cyclic stability highlight the promise of this molecular sieving material for industrial C2H2 separation.
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