Hierarchical Oriented Metal–Organic Frameworks Assemblies for Water‐Evaporation Induced Electricity Generation

Abstract

Advances in metal–organic frameworks (MOFs) are stimulating interest in water‐evaporation induced electricity generation. Establishing design principles for desirable MOFs and revealing the structure‐activity relationship is essential to development of this field. Around this key issue, herein the concept of “hierarchical oriented MOFs” is proposed and the Cu(BDC‐OH) MOFs are organized into hierarchical oriented assemblies by successively using methods of hydrolysis, anion exchange reaction, and heteroepitaxy growth. It is discovered that this hierarchical oriented Cu(BDC‐OH) assemblies‐based generator containing long‐ranged ordered microporous channels exhibits a voltage of 0.6 V and electricity output of 1.56 nW cm–2 in the natural state of water evaporation. Finite element analysis and density functional calculation elucidate that hierarchical oriented structure of Cu(BDC‐OH) MOFs with certain surface charge density have an “aggregation effect,” dominating the final output voltages. This work not only offers valuable theoretical guidance for exploring self‐assembly of MOFs superstructures and water‐evaporation induced electricity generation, but also may open interesting perspectives for understanding some fundamental questions about structure‐activity relationship in MOFs materials science.

Materials for evaporation‐driven hydrovoltaic technology

“…(C) Construction process of hydrovoltaic device based on layered Cu (BDC‐OH) MOFs. [ 74 ] Copyright 2021, Wiley‐VCH. (D) The synthetic process of Cu‐BTC nanorod arrays.…”

“…These results indicated that MOFs, 1D porous nanomaterials with a certain density of surface charge, had an “aggregation effect” through layered directional treatment, which could play an important role in evaporation‐driven electricity generation. [ 74 ] However, degradation of MOFs usually occurs on surfaces with defects or no functional groups, causing instability in water. [ 76 ] As shown in Figure 7D, Li et al designed a hybrid membrane, which combined MOFs (Cu‐BTC complex nanorod arrays) with polyaniline (PANI) conductive polymers to improve the stability of MOFs.…”

“…[97,98] Ma et al prepared a novel AlOOH/UIO-66 hybrid nanomaterial by the growth of UIO-66 nanoparticles on AlOOH nanoflakes, which structures were similar to LDHs. [20] After that, hierarchical oriented Cu (BDC-OH) MOFs assemblies-based EHDs containing long-ranged ordered microporous channels that V oc increased significantly from 0.3 to 0.6 V. [74] Oriented continuous nanochannels have the characteristics of reducing flow resistance and enhancing fluid transport capacity.…”

Harvesting Water‐Evaporation‐Induced Electricity Based on Liquid–Solid Triboelectric Nanogenerator

“…The water‐evaporation‐induced electricity generates accompanying the liquid–solid triboelectrification. [ 24 ] Inspired by this work, researchers improved the performance of the generator by optimizing its materials, [ 25 , 26 , 27 ] structure, [ 28 , 29 , 30 , 31 ] fabrication process [ 32 , 33 , 34 ] or their combinations. [ 2 , 35 , 36 ] The excellent water‐evaporation electricity nanogenerators have significantly improved its key performance indicators such as open‐circuit voltages (<2 V), short‐circuit current (<1 µA).…”

Microfluidic Salinity Gradient-Induced All-Day Electricity Production in Solar Steam Generation

“…Along with the freshwater scarcity, energy is also a big challenge to humanity due to its high demand and limited sources. , Over the past few years, significant efforts have been invested in producing energy together with solar steam generation. ,− For example, the temperature difference between the evaporative surface and bulk water was used to produce thermoelectricity. − Also, by exploiting the enthalpy of the vapor, Li et al were able to generate a maximum open-circuit voltage ( V OC ) of 4.15 V and a short-circuit current ( I SC ) of 0.61 A at a solar intensity of 30 sun . Furthermore, using an ion-selective membrane, Zhou and co-workers have obtained a V OC of 84 mV at a solar intensity of 2 sun from the salinity gradient caused by the water evaporation .…”