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Mid‐infrared spectroscopy is often used to identify material. Thousands of spectral points are measured in a time‐consuming process using expensive table‐top instrument. However, material identification is a sparse problem, which in theory can be solved with just a few measurements. Here the sparsity of the problem is exploited to develop an ultra‐fast, portable, and inexpensive method to identify materials. In a single‐shot, a mid‐infrared camera can identify materials based on their spectroscopic signatures. This method does not require prior calibration, making it robust and versatile in handling a broad range of materials.

A radiative vapor condenser sheds heat in the form of infrared radiation and cools itself to below the ambient air temperature to produce liquid water from vapor. This effect has been known for centuries, and is exploited by some insects to survive in dry deserts. Humans have also been using radiative condensation for dew collection. However, all existing radiative vapor condensers must operate during the nighttime. Here, we develop daytime radiative condensers that continue to operate 24 h a day. These daytime radiative condensers can produce water from vapor under direct sunlight, without active consumption of energy. Combined with traditional passive cooling via convection and conduction, radiative cooling can substantially increase the performance of passive vapor condensation, which can be used for passive water extraction and purification technologies.