Mixed N,O-donor Directed Blue Emissive Nano-dispersed Mesoporous Mn(II)-MOF: Dual Sensing Probe for Recyclable and Ultrasensitive ppb-Level Recognition of TNP and Cr(VI)-Oxoanions.

A new mesoporous Mn(II)-MOF [Mn 2 (phen) 2 (nia) 2 ] ∞ with 4-c uninodal net topology and reiterating rectangular channels in its cargo-net like extension was synthesized using π-conjugated phenanthroline (phen) and syn-syn bridging 5-nitroisopthalic acid (nia) linkers. The MOF (1) exhibited phase purity, uniform morphology, photo and thermal stability, and robustness; duly triggered by the exceptional framework rigidity via intermolecular H-bonding and interlayer π-π stacking interactions. The bright-blue luminescence of the MOF nano-dispersion was explored for sensitive, specific and ultrafast detection of trinitrophenol (TNP) with extremely low LOD (90.62 nM), high K SV (18.27×10 4  M -1 ) and Kq (4×10 14  M -1 s -1 ). The vapor-phase TNP sensing was also accomplished. Additionally, 1 served towards discriminatory, aqueous-phase monitoring of Cr(VI)-oxoanions, depicting LODs: 36.08 and 35.70 ppb; K SV : 3.46×10 4 and 4.87×10 4  M -1 ; Kq: 3.26×10 13  M -1 s -1 and 4.31×10 13  M -1 s -1 ; and response time: 32 and 40s for CrO 4 2- and Cr 2 O 7 2- respectively. The quenching mechanisms (i. e., RET, PET, IFE, weak interactions, collisional quenching and π⋅⋅⋅π stacking) was explained from several experimental investigations and theoretical DFT calculations. The recyclable sensing events and quantification from complex environmental matrices with admirable recovery rates and high K SV (13.02-22.44×10 4 ; ~6.31-10.98×10 4 and ~6.60-11.42×10 4  M -1 for TNP, CrO 4 2- and Cr 2 O 7 2- ) undoubtedly advocated the consistency of the probe.