Direct air capture of CO2 for solar fuel production in flow

Abstract

Direct air capture is an emerging technology to decrease atmospheric CO₂ levels, but it is currently costly and the long-term consequences of CO₂ storage are uncertain. An alternative approach is to utilize atmospheric CO₂ on-site to produce value-added renewable fuels, but current CO₂ utilization technologies predominantly require a concentrated CO₂ feed or high temperature. Here we report a gas-phase dual-bed direct air carbon capture and utilization flow reactor that produces syngas (CO + H₂) through on-site utilization of air-captured CO₂ using light without requiring high temperature or pressure. The reactor consists of a bed of solid silica-amine adsorbent to capture aerobic CO₂ and produce CO₂-free air; concentrated light is used to release the captured CO₂ and convert it to syngas over a bed of a silica/alumina-titania-cobalt bis(terpyridine) molecular-semiconductor photocatalyst. We use the oxidation of depolymerized poly(ethylene terephthalate) plastics as the counter-reaction. We envision this technology to operate in a diurnal fashion where CO₂ is captured during night-time and converted to syngas under concentrated sunlight during the day.