Moisture-tolerant diamine-appended metal–organic framework composites for effective indoor CO2 capture through facile spray coating

Abstract Reducing the concentration of indoor carbon dioxide (CO2) to an acceptable safe level of 1,000 ppm is an important issue because a high level of CO2 in closed spaces causes lethargy and fatigue. Although diamine-functionalized metal–organic framework (MOF) adsorbents with high CO2 capacities under indoor air conditions are available, the moisture-induced degradation of MOFs and their shaping remains a challenge for practical applications. Herein, we report the fabrication of epn-functionalized Mg2(dobpdc) composites, which proceeded by mixing with a polystyrene-block-polybutadiene-block-polystyrene (SBS) hydrophobic polymer (epn = 1-ethylpropane-1,3-diamine; dobpdc4− = 4,4′-dioxido-3,3′-biphenyldicarboxylate). The composites were successfully shaped in the form of membranes with different amounts of MOF (epn-MOFX@SBS; X  = 60–80 wt%). Specifically, epn-MOF80@SBS exhibited a significant CO2 adsorption of 2.8 mmol g−1 at 1,000 ppm with recyclable working capacity. The composites were further coated on the surfaces of different supports, such as a Ti mesh, an air filter, and granular activated carbon via a facile and simple spraying method. The experimental conditions were 1,000 ppm CO2 and 60% relative humidity in a 50-L chamber; the coated materials displayed invariant CO2 removal performances over 10 cycles and even after 7 days of exposure. The recyclable and long-term CO2 adsorption capacities demonstrate that the MOF-polymer composites and their coating on various supports provide a useful and effective route for indoor CO2 capture under realistic conditions.