In a paper appearing this week in ACS Central Science, a journal of the American Chemical Society, UC Berkeley’s Omar Yaghi and his colleagues describe the latest version of their water harvester, which can pull more than five cups of water (1.3 liters) from low-humidity air per day for each kilogram (2.2 pounds) of water-absorbing material, a very porous substance called a metal-organic framework, or MOF. That is more than the minimum required to stay alive. During field tests over three days in California’s arid Mojave Desert, the harvester reliably produced 0.7 liters per kilogram of absorber per day — nearly three cups of clean, pure H2O. That’s 10 times better than the previous version of the harvester.