Tale of COF-on-MOF Composites with Structural Regulation and Stepwise Luminescence Enhancement

Abstract

Integrating metal−organic framework (MOF)− covalent organic framework (COF) allows versatile engineering of hybrid materials with properties superior to pristine components, especially COFs suffered from aggregation-caused quenching (ACQ), unlocking more possibilities to improve the luminescence of COFs. In this work, we prepared various MOF@ COF composites with different COF layer thicknesses, in which stable UiO-66-NH 2 served as the inner substrate and 1,3,5benzenetricarboxaldehyde (BT), and 3,3′-dihydroxybenzidine (DH) were used to construct a COF layer. In addition to the conventional preparation method, we increased the ratio of BT and DH to be 1:2.5, and impressively, the morphologies of acquired UC (1:2.5) materials were quite different from the previous reticular structure and gradually extended from the spherical structure to the prickly structure with the increase of COF monomers. Remarkably, all of the UC materials possessed better luminescence properties than individual COF due to the limited COF layers. Meanwhile, UC-1 materials with an optimal COF layer displayed the strongest emission. In comparison with a single COF, the quantum yields of UC-1 and UC-1 (1:2.5) were increased nearly 7 times and 5 times, respectively. Moreover, the fluorescence of UC-1 materials was progressively enhanced via selective F − sensing. This work is expected to shed light on the potential hybridization of MOF−COF with structural adjustment, morphological design, and luminescence enhancement.

Reticular framework materials for photocatalytic organic reactions

“…Compared to single MOFs or COFs, MOF-COF heterostructures may exhibit excellent performances in the field of photocatalysis due to the efficient interfacial electron transfer and synergy of their different components. 329 In the case of most MOF-COF composites, the MOFs are used as the core and the COFs are always coated as the shell, probably because the covalent bond connected network with high stability can provide stronger protection for the materials. In particular, the interface of MOF-COF composites is mainly constructed via the formation of imine bonds (-CQN-) between the aldehyde monomers of COFs and the reserved -NH 2 groups of MOFs, such as NH 2 -MIL-125 and NH 2 -UiO-66.…”

Covalent Organic Frameworks (COFs) as Multi-Target Multifunctional Frameworks

“…COFs have high thermal stabilities, possessing low mass densities with permanent porosity as they are constructed from light-weight elements connected together through strong covalent bonds [ 8 ]. Different aspects of COFs have been investigated, reviewed, and reported by a number of researchers [ 9 , 10 , 11 , 12 , 13 ]. COFs are further classified into two categories depending on their building block dimensions:…”

Rational design of COF–MOF composites for ratiometric fluorescence detection of phosphate

“…Integrating COF-MOF hybrid materials is an effective way to develop a ratiometric fluorescence method. [25][26][27][28][29][30] To date, several MOF-COF or COF-MOF composites have been designed and prepared; [31][32][33][34][35] however, lanthanide organic frameworks have never been reported to integrate COFs to form composites and they still face some challenges: 1. a layer-by-layer stacked structure and intramolecular rotation in a single layer hinder the emission of COFs; 2. COFs with metal ion binding sites such as carboxyl groups are important for preparing COF-MOF hybrid materials; 36 and 3.…”