Photocatalytic reduction of CO2 in water using a single integrated system utilizing sunlight is the ultimate goal for artificial photosynthesis. Here, we report the design and multistep synthesis of Zr-MBA-Ru/Re-MOF...

Insights into developing innovative routes for the stabilization of photogenerated charge-separated states by suppressing charge recombination in photocatalysts is a topic of immense importance. Herein, we report the synthesis of a metal−organic framework (MOF)-based composite where CdS nanoparticles (NPs) are confined inside the nanosized pores of Zr 4+ -based MOF-808, namely, CdS@MOF-808. Anchoring L-cysteine into the nanospace of MOF-808 via postsynthetic ligand exchange allows the capture of Cd 2+ ions from their aqueous solution, which are further utilized for in situ growth of CdS NPs inside the nanosized MOF pores. The formation of CdS@MOF-808 opens up a possibility for visible-light photocatalysis as CdS NPs (1−2 nm) are a well-studied semiconductor system with a band gap of ∼2.6 eV. The confinement of the CdS NPs inside the MOF pores, close to the Zr 4+ cluster, opens up a shorter electron transfer route from CdS to the catalytic Zr 4+ cluster and shows a high rate of H 2 evolution (10.41 mmol g −1 h −1 ) from water with a loading of 3.56 wt % CdS. In contrast, a similar composite in which CdS NPs are stabilized on the external surface of MOF-808 reveals poor activity (0.15 mmol g −1 h −1 ). CdS NPs stabilized on the MOF-808 surface show slower and inefficient electron transfer kinetics compared to CdS stabilized inside the nanospace of the MOF, as realized by the transient absorption measurements. Therefore, this work unveils the critical role of stabilizing the photosensitizer NPs in close proximity of the catalytic sites in MOF systems towards developing highly efficient H 2 evolution photocatalysts.

Here, we demonstrate mimicking of photophysical properties of native green fluorescent protein (gfp) by immobilizing the gfp chromophore analogues in nanoscale MOF-808 and further exploring the bioimaging applications. The two virtually nonfluorescent gfp chromophore analogues carrying different functionalities, BDI-AE (COOH/COOMe) and BDI-EE (COOMe/ COOMe) were immobilized in nanosized MOF-808 via postsynthetic modification. An 1 H NMR and IR study confirms that BDI-AE was coordinated in NMOF-808, whereas BDI-EE was just noncovalently encapsulated. Interestingly, the extremely weakly fluorescent monomers BDI-AE and BDI-EE (QY = 0.01−0.03%, lifetime = 0.01−0.03 ns) showed a 10 2 -fold increase in quantum efficiency with a significantly longer excited-state lifetime (QY = 1.8−5.6%, lifetime 0.89−1.49 ns) after immobilization in the NMOF-808 scaffold.

In recent years, extensive research has been directed toward the successful preparation of nanoscale luminescent thermometers with high sensitivities operative in a broad temperature range. To achieve this goal, we have devised a unique design and facile multistep synthesis of Zr-ctpy-NMOF@ Tb x Eu y compounds by confining Ln-complexes (Ln = Eu 3+ /Tb 3+ ) into a robust nanoscale Zr-NMOF (MOF-808) via postsynthetic modification. Covalent grafting of 4-(4′-carboxyphenyl)-2,2′:6,2″terpyridine ligand (ctpy) with a high triplet state energy and corresponding immobilization of bimetallic Ln 3+ ions resulted in yellow light-emitting Zr-ctpy-NMOF@Tb 1.66 Eu 0.14 to achieve a sensitivity of 5.2% K −1 (thermal uncertainty dT < 1 K) operative over a broad temperature range of 25−400 K. To defeat the odds related to the detection of minute temperature changes using luminescent materials, we prepared a white light-emitting Zr-ctpy-NMOF@Tb 1.4 Eu 0.31 that showed temperature-modulated multispectrum chromism where the color drastically changes from green (at 25 K, Q.Y.: 20.21%) to yellowish-green (at 200 K, Q.Y.: 23.13%) to white (at 300 K, Q.Y.: 26.4%) to orange (at 350 K, Q.Y.: 26.93%) and finally red (at 400 K, Q.Y.: 28.2%) with a high energy transfer efficiency of 49.8%, which is further supported by electron−phonon coupling.