Strategic Design of Non-d 10 Luminescent Metal-Organic Frameworks as Dual-Mode Ultrafast and Selective Sensing Platforms for Aldehydes at the ppb Level.

Utilizing a cautious design of luminescent MOFs of non-d 10 divalent transition metals based on two factors (metal nodes in an octahedral geometry to minimize nonradiative energy dissipation and tailored organic chromophores), this work reports {[Ni 2 (oxdz) 2 (tpbn)]} n ( 1 ), {[Ni 2 (oxdz) 2 (tphn)]} n ( 2 ), and {[Ni 2 (oxdz) 2 (tpon)]} n ( 3 ), synthesized at room temperature, varying the spacer length of tpbn/tphn/tpon (four, six, and eight CH 2 groups, respectively). This subtle change in 1 - 3 is correlated to their hydrophobicity and polarizing power via water vapor sorption and selective and sensitive detection of aldehydes at the ppb level, respectively. A decrease in water vapor uptake (14.8, 8.95, and 3.19 mmol g -1 for 1 - 3 , respectively) is observed with an increase in their hydrophobicity. On the other hand, the solution phase detection limits of acetaldehyde and benzaldehyde (2.42 and 6.71 ppb for 1 , 2.77 and 4.08 ppb for 2 , and 10.35 and 10.4 ppb for 3 , respectively) show a similar trend for their polarizing power. The best performance of 1 is expanded to the vapor-phase detection of acetaldehyde (297% luminescence enhancement) under different pH conditions. The second mode of detection of acetaldehyde via the metal-centered electrochemical behavior of 1 provides detection limits of 38.2 and 71.5 ppb at pH 7 and 13, respectively.