Better Contact S-Guest/S-Host R-Guest/S-Host with absolute CD signal of 10-20 mdeg (0.1 mM). The absorption (Figure ) and emission spectra (Figure ) in dilute dichloromethane (CH2Cl2) show that 4FMNNI set exhibit intense (Figure , Table ) fluorescence while 4FBrBI have no discernible emission, likely due to the heavy-atom effect. At 77 K, 4FBrBI displays phosphorescence with a lifetime of several milliseconds, while 4FMNNI exhibits no appreciable delayed emission (Figure ), suggesting its low intrinsic phosphorescence yield. The chiral selector R-4FBrBI was first examined as a solidstate host: cyan fluorescence (circa 491 nm,  = 3.62 ns) and red RTP (circa 615 nm) arise simultaneously constituting a visibly white emission color when R-4FMNNI (10 ppm, w/w, see SI for detailed protocols) is mixed with the selector medium (R@R, Figure ). Surprisingly, when its enantiomer (S-4FMNNI) is applied to the R-4FBrBI selector, only fluorescence occurs with no distinguishable RTP. Delayed emissions (DE) show that the enantiomeric RTP enhancement ratio (ef = IRR/ISR) is 139.9 (Figure ), with an R@R RTP lifetime of 73.31 ms (Figure , Table ). Subtraction of the background host signal from the total RTP gives an ef∆ (∆IRR/∆ISR = [IRR-IR]/[ISR-IR]) of 196.6 (Figure ). The achieved RTP chiral recognition via organic chiral solids (OSC), which is essentially an "on-off" mode. DE spectra excited with 365-nm light display lower ef values due to host RTP interference (Figure and S12-14). The selector host S-4FBrBI, the enantiomer of R-4FBrBI, can also achieve enantioselectivity as shown in Figure , where a "mirrorimage relation" of RTP responses is observed toward the enantiomers of the 4FMNNI, i.e., ef (ISS/IRS) = 155.3 with an RTP lifetime of 70.55 ms for S@S confirms the consistency of the chiral recognition method using the guest-host system.