ACR Journal

CMYK / .ai CMYK / .ai CMYK / .ai acrjournal.uk 27 AIR TREATMENT porosities (up to 10,000m 2 /g). They can be developed to target everything from ethylene and ammonia to carbon dioxide and methane from complex gas mixtures. Creating healthier, more productive air Given the tuneable properties of MOFs and their ability to hold vast amounts of medium, the implication for creating better indoor environments is clear. In schools, for example, these products could be used to specifically target and capture the carbon dioxide that can quickly build up in the average 30-seat classroom. For example, one teacher in Surrey found that CO 2 levels rocketed after double lessons with the windows closed. In just 90 minutes, levels had reached 2,300 parts per million (ppm), or 0.23 per cent of the air, far exceeding the normal level of circa 400ppm. This is far from a trivial issue, particularly in education, where the ability to concentrate is closely linked with future academic success. For example, research from Harvard University in 2016 found that, on average, a typical participant’s cognitive scores dropped by 21 per cent when the room’s CO 2 was increased by just 400ppm beyond baseline concentration. In addition, critical response, information usage and strategy plummeted, all of which are key indicators of higher-level function and decision-making. Unsurprisingly these results also pose problems for the corporate workforce, especially in countries where productivity is low, and the ongoing challenge of sick building syndrome (SBS) costs businesses millions in missed working days every year. While the exact causes of SBS are still up for debate, some have identified the outgassing of materials from newspapers, furniture and building fabric as a possible candidate for the chronic symptoms people suer, as well as volatile organic compounds released from things like aerosols, solvents and disinfectants. Fortunately, MOFs can also play a role here with their ability to capture specific problem molecules while bypassing others needed for good indoor air quality. Some might argue that simply opening the windows is sucient, especially when tackling CO 2 build up in small classrooms. In many cases, this will be eective; however, depending on the season, natural ventilation may not be possible due to either very high or very low external temperatures. Likewise, in other environments such as large lecture theatres or oce blocks, there won’t be any windows to open, and fresh air will be provided through a fitted ventilation system. It’s also important to note that some inner-city buildings will be found next to busy roads where outdoor air quality is poor and noise is high, so other methods will be necessary. As such, there is a broad range of everyday scenarios where fitted ventilation is the only way to refresh air while sustaining a comfortable and healthy ambient indoor temperature. Efficiency Using MOFs to improve air quality also benefits buildings with demand-control ventilation (DCV). These systems optimise indoor air quality through sensor-based airflow management, providing rooms with the right amount of fresh air when it is needed. In an ideal world, DCVs would recycle 100per cent of the air they use, but the CO 2 that naturally builds up over time means more has to be introduced at certain times. Introducing a MOF-based material into an existing DCV system oers a route out of this problem. Building managers, for example, could easily retrofit their existing HVAC systems, removing CO 2 without the need for invasive modifications to their current system. In addition, the unique properties of MOFs allow them to be easily regenerated and reused, continuously removing CO 2 and maintaining ideal conditions. The same principle applies to air travel when air is recycled back into the passenger cabin during a flight. Perhaps the most significant benefit of this strategy is the ability to reduce the amount of energy used for temperature control during hotter months. For example, a typical oce building in the summer will use air conditioning to cool a room and introduce warmer outdoor air to ensure CO 2 is kept within an acceptable range. With MOFs, though, more of the already-cooled air could be recycled back into the system without the need to worry about pollutants, in turn lowering the cooling duty and energy penalty incurred. This approach would prove especially eective in countries that experience more prolonged periods of warm weather and rely heavily on HVAC systems. More attention is now given to the air that we breathe. This is due to the emerging research and the eect of the COVID-19 pandemic, which has helped to make an explicit link between indoor conditions and people’s health. With society slowly returning to something resembling normality, now seems like an ideal opportunity to explore better strategies for managing the air in oces, schools and other buildings where large groups of people meet. https://www.moftechnologies.com/