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Crystallinities/morphologies of nano-/micromaterials are decisive features for their applications and can be controlled by both kinetics and thermodynamics. Adding competitors as reversible terminators/inhibitors slows down the reaction, permitting thermodynamic control of the reaction and generation of more ordered products. Here, we introduce a reversible polycondensation-termination method to switch a kinetically controlled (irreversible) reaction to thermodynamic control for the synthesis of an emerging nanoporous material, specifically a 2D covalent organic framework with high crystallinity and well-defined morphology.

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TiO2 nano-sheet film (TiO2 NSF) was prepared by a hydrothermal method. Ag nanoparticles (NPs) were then deposited on the surface of TiO2 NSF (Ag/TiO2 NSF) under microwave-assisted chemical reduction. The prepared samples were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible (UV-vis) absorption spectroscopy, x-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectroscopy, and Raman scattering spectroscopy. The results revealed that the Ag NPs were well dispersed on the anatase/rutile mixed-phase TiO2 nano-sheet surface with a metallic state. The visible light absorption and Raman scattering of TiO2 were enhanced by Ag NPs based on its surface plasmon resonance effect. Besides, Ag NPs could also effectively restrain the recombination of photogenerated electrons and holes. Photocatalytic water splitting was conducted on the films to obtain hydrogen, and the experimental results indicated that plasmonic Ag NPs could greatly enhance the photocatalytic activity of TiO2 due to the synergistic effect between electron transfer and surface plasmon resonance enhanced absorption. The hydrogen yield obtained from the optimal sample reached 8.1 μmol cm(-2) and the corresponding energy efficiency was about 0.47%, which was 8.5 times higher than that of pure TiO2 film. Additionally, the formation mechanism of TiO2 nano-sheet film is preliminarily discussed.

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Three water-stable luminescent MOFs [Zn4(bptc)2(NMP)3(DMF)­(H2O)2] n (1-a), [Cd4­(bptc)2­(NMP)3­(DMF)2­(H2O)1] n (1-b), and {[Zn2­(bptc)­(DMA)­(H2O)2]·​(DMA)2·​H2O} n (2), possessing similar chemical components (M2:L1:Sol3) and topology structures, were synthesized by solvents control. Their excellent sensing on iron­(III) cation and nitroaromatic explosives (NACs) with great selectivity, sensitivity and a high K sv (4.54 × 104 for 1-b on PNP) were observed by quenching effects. Furthermore, Zn-MOFs exhibit interesting stimuli-responsive luminescence enhancement after the encapsulation of a series of IIIB cations stimulated different luminescent emitting and intensity enhancement through host–guest processes of the pores in MOFs, especially for two distinct responses of Zn-MOF on a Tb3+ cation.