Trace-doped metal–organic gels with remarkably enhanced luminescence

A novel approach has been proposed to fabricate MOF-based luminescent gel materials with trace amounts of doping in order to study the role of trace defects in metal–organic gel materials. UiO-66-based ZrBDC (BDC = 1,4-benzene dicarboxylate) gels were first prepared from Zr4+ and H2BDC under mild conditions, and subsequently trace doping (as low as 0.01 mol%) of the ZrBDC gel materials with H4TCPE (tetrakis(4-carboxyphenyl)ethylene) was achieved successfully. The resulting ZrBDC–TCPE0.01% gel material features mild synthetic conditions and retains the high porosity of parent UiO-66 gel materials. Moreover, trace doping causes a remarkable change to the luminescence properties and the gel emits blue luminescence with high quantum yield (59%). ZrBDC–TCPE0.01% shows responses with high sensitivity and selectivity for nitroaromatics (picric acid) in the aqueous phase and detects picric acid as low as parts per billion (24 ppb). The present luminescent gel materials provide new insights into developing functional metal–organic materials through trace defects, which may remarkably alter the properties of metal–organic materials.