Processing metal-organic frameworks (MOFs) as films with controllable thickness on asubstrate is increasingly crucial for many applications to realizef unction integration and performance optimization. Herein, we report af acile cathodic deposition process that enables the large-area preparation of uniform films of zeolitic imidazolate frameworks (ZIF-8, ZIF-71, and ZIF-67) with highly tunable thickness ranging from approximately 24 nm to hundreds of nanometers. Importantly,t his oxygen-reduction-triggered cathodic deposition does not lead to the plating of reduced metals (Zn and Co). It is also operable cost-effectively in the absence of supporting electrolyte and facilitates the construction of well-defined submicrometer-sized heterogeneous structures within ZIF films.Metal-organic frameworks (MOFs), ac lass of porous crystalline materials with large surface areas,r egular pore sizes,a nd tailorable surface chemistry, [1] have received considerable attention in av ariety of fields. [2][3][4][5][6][7][8] Form any applications,s uch as separations, [3] energy storage [5] and conversion, [6] chemical sensing, [7] and electronics, [8] it is often necessary to process MOF materials as films on as pecific substrate.A mong methods established for preparing MOF films, [9,10] strategies based on electrochemical synthesis are attractive for many advantages including technological flexibility,scalable preparation, and industrial production potential. [11] Nevertheless,t heir potential for preparing MOF films with precisely tunable morphology and thickness has not been fully explored. These variables,h owever,a re critically important for structure integration and performance optimization in (especially device) applications. [8,9] MOFs could be deposited on the electrode surface anodically [12] or cathodically. [13] In cathodic deposition, reduction of some special molecules or ions (e.g.n itrate ions) on electrode surface results in an increase in pH, which promotes the deprotonation of organic ligands and induces the formation of MOFs.Atfirst glance,cathodic deposition appears to be attractive for the direct synthesis of MOFs on conductive substrates.H owever,r eports on the cathodic deposition of MOFs are comparably few.The challenge arises from the more negative reduction potential of nitrate ions relative to those of some important metal ions,f or example, Zn II ,C o II ,a nd Cu II ,w hich constitute the most extensively studied MOFs. [13b,g] As ar esult, cathodic deposition of these MOF materials is commonly accompanied with plating of the corresponding metals, [13a,e] which is in most cases undesirable.Herein, we report the first cathodic deposition of zeolitic imidazolate framework materials (ZIFs), an important subgroup of MOFs that have been extensively studied owing to their outstanding thermal stability and chemical robustness. [14,15] Our strategy is based on an oxygen reduction triggered-electrochemical-chemical-reaction Scheme responsible for the formation of ZIF materials (Scheme 1). Electrochemical oxyge...
Microporous metal–organic frameworks (MOFs) are promising candidate materials for chemical sensing, but the reproducible fabrication of MOF-based sensors with optimized and stable performances remains a significant challenge. Here, we report the fabrication of MOF optical sensors with steady but tunable optical properties via assembling UiO-66 crystals with controllable sizes and missing-linker defects. The well-defined but tunable microscopic and mesoscopic structural features of MOF sensing components greatly facilitate the optimization of device performance. The UiO-66 crystal-assembled sensors display fast response (2.00 s) and short recovery (3.00 s) to ethanol vapor (one of the analytes we tested). Our systematical investigation indicates that the mesoporous features of sensing components contribute greatly to the enhanced sensitivity (by ∼24.6% to the saturated ethanol vapor), response speed (by ∼42.9%), and recovery speed (by ∼59.7%) of the crystal-assembled sensors in comparison to their dense counterpart. The building crystal sizes show a slight influence on the response speed but profound effects on the sensitivity and recovery performances of sensors. The missing-linker defects have obvious beneficial effects on the desorption kinetics of analyte and can cause a faster recovery of sensors.
This paper aims to discuss cross-cultural empathy and ways to promote the development of empathy in various cultures. Empathy is considered one of the most indispensable traits in every society. However, the concept of empathy differs in different communities, due to social, cultural, and religious influences. According to Mencius, empathy contributes to the expansion of moral cultivation. A core concept in Confucianism, benevolence (Ren), represents the relationship between people. The practice of compassion requires the ability to conduct moral reasoning. The development of such an ability relies heavily on empathy. Since empathy is crucial to people’s daily life in developing critical skills and relationships, fostering empathy in different cultures is helpful. Even though empathy varies significantly in many ways among different cultures, it possesses some fundamental similarities in all of them. The Golden Rule is an excellent example of an ethical principle that could be found in almost all civilizations. Respecting the differences in various cultures, learning more about other cultures and their social norms, and avoiding talking about sensitive topics can help people become more empathetic.
Processing metal–organic frameworks (MOFs) as films with controllable thickness on a substrate is increasingly crucial for many applications to realize function integration and performance optimization. Herein, we report a facile cathodic deposition process that enables the large‐area preparation of uniform films of zeolitic imidazolate frameworks (ZIF‐8, ZIF‐71, and ZIF‐67) with highly tunable thickness ranging from approximately 24 nm to hundreds of nanometers. Importantly, this oxygen‐reduction‐triggered cathodic deposition does not lead to the plating of reduced metals (Zn and Co). It is also operable cost‐effectively in the absence of supporting electrolyte and facilitates the construction of well‐defined sub‐micrometer‐sized heterogeneous structures within ZIF films.
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