Ambient temperature NO2 removal by reversible NO2 adsorption on copper-based metal-organic frameworks (MOFs)-derived nanoporous adsorbents

Nitrogen dioxide (NO2) is a potent atmospheric pollutant generated from fossil fuel combustion at power plants, industrial plants, and vehicles, which raises serious health concerns (e.g., respiratory diseases) and contributes to severe environmental pollution issues (e.g., acid rain and ground-level ozone). Adsorption is an efficient approach for ambient temperature NO2 removal, whose efficiency highly depends on the design of the adsor-bents. The widely reported activated carbon adsorbents suffer from low and typically irreversible NO2 capacity apart from co-generation of considerable amounts of polluting NO (up to 50% of adsorbed NO2), which is released back into the atmosphere. Herein we report copper-based metal-organic framework (MOF)-derived carbon materials (i.e., Cu@C(CuBTC) and Cu@C(CuBDC)) featuring high NO2 capacity coupled with minimal release of NO and outstanding reusability for NO2 removal under ambient temperature. Both Cu@C(CuBTC) and Cu@C(CuBDC) showed an impressive improvement (up to 13.5 times) in NO2 capacity over their pristine MOFs counterparts, with Cu@C(CuBTC) showing the highest NO2 capacity (4.97 mmol/g) and minimal (<20 % of adsorbed NO2) release of NO in this study. Such a massive improvement in the NO2 capacity of carbonized composites is attributed to highly active and homogenously dispersed Cu nanoclusters, which serve as adsorption sites and play the dominant role in NO2 removal. Further, for the first time, Cu@C(CuBTC) exhibited outstanding reusability for NO2 removal under humid conditions, reflected by stable NO2 capacity in the cyclic adsorption tests (5 cycles), suggesting a great potential for real-world applications. This study provides a general and facile strategy for designing highly dispersed, water-resistant, and stable copper nanoclusters on carbon support for efficient adsorptive removal of various toxic gases under ambient temperature.