Aryl boronic acids are a broad class of organic intermediates. Here, we show that their cyclic-esterification with appropriate dihydric alcohols is a simple and effective approach for screening organic room-temperature phosphorescent (RTP) and mechanoluminescent (ML) materials. Non RTP and ML active 4-(carbazol-9-yl)phenylboronic acid can be made into long-lived RTP emitters with lifetimes of 264 and 430 ms and a bright ML dye with blue emission by cyclic-esterification with 1,3-propanediol, 2,2-dimethyl-1,3-propanediol, and glycol, respectively. Systematic single crystal analysis and quantum chemical calculations indicate that cyclic borates dominate the molecular packing structures and intermolecular interactions, which is responsible for the different optical properties.