Aliphatic Aldehyde Detection and Adsorption by Nonporous Adaptive Pillar[4]arene[1]quinone Crystals with Vapochromic Behavior.

The detection and adsorption of volatile low-molecular-weight aliphatic aldehydes is of significance, owing to their physical volatility, chemical toxicity, and widespread applications in chemical industrial processes. Here, nonporous adaptive pillar[4]arene[1]quinone (EtP4Q1) crystals with vapochromic behavior are used for the volatile aliphatic aldehyde uptake and sensing. When desolvated EtP4Q1 crystals (EtP4Q1α) are exposed to aliphatic aldehydes with different carbon chain lengths, they quantitatively adsorb vapors of these aldehydes, accompanied by different color changes. Crystal structure analyses show that the structure of EtP4Q1 transforms from EtP4Q1α into the corresponding new structures after the adsorption of these aldehydes, which leads to different color changes. The selectivity of EtP4Q1α crystals, which function as both sensors and adsorbents upon exposure to mixed aldehyde vapors, is also explored. Finally, it is demonstrated that EtP4Q1α crystals can be recycled many times without loss of performance.