Enhanced photoluminescence quantum yield of terbium nano-MOFs synthesized by microwave assisted solvothermal method

In the present work luminescent metal–organic frameworks consisting of terbium ions as the metallic center and 1,4 benzene-dicarboxylic acid (BDC), benzene-tricarboxylic (BTC) acid and 1,3 thiophane-dicarboxylic acid (TDC), as the organic ligands, are synthesized by the microwave assisted solvothermal method at a relatively short time. The samples are studied before and after a thermal annealing process at 400°C. The structural and chemical analysis indicate the formation of nanocrystals of about 8.8 nm, 5.0 nm and 127 nm for BDC, BTC and TDC samples, respectively. All the samples show carbon and oxygen in excess attributed probably to remnants of the N,N-Dimetilformamide used as solvent during the synthesis or to diffused particles from the atmosphere. The luminescent analysis shows a high quantum yield value for the BDC framework, 99.6%, after the annealing process, attributed to an antenna effect; whereas both the BTC and TDC samples show a higher quantum yield before annealing; 64.1% and 13.3%, respectively. The luminescence decay time is also computed in the samples resulting between 1 and 1.5 ms for both BDC and BTC samples, whereas for the TDC sample the decay time was about 0.2 ms. A noticeable daylight visible PL emission is observed in all samples.