A thiazolo[5,4-: D] thiazole-bridged porphyrin organic framework as a promising nonlinear optical material

Porphyrin-based porous organic frameworks are an important group of materials gaining interest due to their structural diversity and distinct opto-electronic properties. However, these materials are seldom explored for nonlinear optical (NLO) applications. In this work, we investigate a thiazolo[5,4-d]thiazole-bridged porous, porphyrin framework (Por-TzTz-POF) with promising NLO properties. The planar TzTz moiety coupled with integrated porphyrin units enables efficient π-conjugation and charge distribution in the Por-TzTz-POF resulting in a high nonlinear absorption coefficient (β = 1100 cm GW-1) with figure of merit (FoM) σ1/σ0 = 5571, in contrast to analogous molecules and material counterparts e.g. metal-organic frameworks (MOFs; β = ∼0.3-0.5 cm GW-1), molecular porphyrins (β = ∼100-400 cm GW-1), graphene (β = 900 cm GW-1), and covalent organic frameworks (Por-COF-HH; β = 1040 cm GW-1 and FoM = 3534). This journal is © The Royal Society of Chemistry

Heated quartz crystal microbalance with highly controlled integration of ZIF-67 for ultra-reliable humidity sensing

The quartz crystal microbalance (QCM) is widely utilized in various fields for detecting parameters such as relative humidity (RH). However, the reliability of QCM as an RH sensor can be compromised by the nonuniform integration of sensing materials and the absence of a dehumidification system for calibration. Damping of the sensor performance may occur due to excessive water molecule adsorption on agglomerated sensing materials, while ineffective desorption of water molecules from these materials renders QCM-based humidity sensors unreliable in highly humid environments. This study presents an innovative approach to achieve area-specific and highly-controlled integration of ZIF-67 on a quartz crystal microbalance (QCM) using electrospray deposition (ESD). The proposed method effectively decorates the sensor surface with exceptional picogram (pg) mass resolution. Additionally, an integrated microheater facilitates rapid sensor heating, eliminating residual water molecules and enhancing the proposed self-recalibration method. The comparative analysis demonstrates that the heated sensor exhibits a remarkable improvement of 47 times in hysteresis and 8 times in drift performance compared to the non-heated sensor. These findings hold great promise for enhancing the reliability of QCM-based humidity sensors, thereby finding utility in diverse research and application fields. © 2023 Elsevier B.V.FALS

Role of Lewis acid metal centers in Metal-Organic Frameworks for ultrafast reduction of 4-nitrophenol

Metal-Organic Frameworks (MOFs) can be a good alternative to conventional catalysts because they are non-toxic and can be selective without compromising efficiency. Nano MOFs such as UiO-66 have proven themselves to be competitive in the catalytic family. In this study, we report the excellent catalytic behavior of UiO-66 MOF in the reduction of a model reaction: 4-Nitrophenol (4-NP) to 4-Aminophenol (4-AP) over MOF-5 (Zn-BDC) and MIL-101 (Fe-BDC). Nano UiO-66 crystals were synthesized by a hydrothermal process and characterized by Powder X-ray Diffraction, Diffused Reflectance UV-Vis spectroscopy, Scanning Electron Microscopy, and Transmission Electron Microscopy. The catalysts' performance during the hydrogenation reduction reaction from 4-NP to 4-AP was investigated in the presence of a reducer, NaBH4. The UiO-66 nano crystals exhibited excellent catalytic behavior owing to its large surface area and Lewis acidic nature at the metal nodes. Furthermore, UiO-66 showed excellent recyclability behavior, verified during repeated consecutive use in a sequence. The catalyst yielded similar catalytic behavior during the reduction of nitrophenols at each cycle, which is a novel finding

Triazine skeletal covalent organic frameworks: A versatile highly positive surface potential triboelectric layer for energy harvesting and self-powered applications

Covalent organic frameworks (COFs) with triazine skeleton have been developed via reticular chemistry. In this present work, a triazine-based nitrogen-rich organic moiety has been used for the COF synthesis and then tested for the output performance of a triboelectric nanogenerator (TENG) using the same. The synthesized COF has been characterized by several physical characterization techniques. For the first time, the surface potential of the prepared COF material was tested experimentally using Kelvin probe force microscopy, which indicates a very high positive triboelectric potential of 2.03 V. The single unit of COF-based TENG delivered 70 V, 0.6 μA, and 38 nC as an electrical output. In the case of multiunit TENG, the current and voltage values are boosted as the parallel connection of four units of TENG gave the peak-to-peak current output rises by 6.3 μA. In comparison, the series connection of four units of TENG gave a high peak-to-peak voltage of 175 V. This work describes the synthesis of N-rich COF material, fabrication of the TENG, and the excellent energy harvesting performance with the realization of low-cost self-powered hand strengthening device. This result paves the way to achieve fruitful exercise monitoring units towards improving lifestyle. © 2022 Elsevier LtdFALS

Significant effect of synthesis methodologies of metal-organic frameworks upon the additively manufactured dual-mode triboelectric nanogenerator towards self-powered applications

Triboelectric nanogenerators (TENG) is an effective approach for the development of self-powered systems, as it offers several flexibilities, such as wide material choice, high power density, simple fabrication process, etc. In this present work, the zeolite imidazole framework (ZIF-8) is synthesized by two approaches: solvent-assisted (SA) and solvent-free (HG), and explored its applicability in TENG devices for energy harvesting. The formation of the highly crystalline ZIF-8 is established from structural and morphological studies. An attempt has been made to understand the surface roughness and surface potential of the synthesized materials that could directly fit their scopes in the addition of the conventional triboelectric series due to their positive surface potential. A cost-effective and facile approach of re-using the waste 3D printing parts is attempted to design vertical contact separation and single electrode mode TENG. The correlation between the material's properties, such as surface potential and surface roughness, supports the ZIF-8 (HG)/Kapton-based dual-mode TENG device to deliver higher electrical output. The triple-unit TENG was designed and fabricated using an additive manufacturing route to achieve a voltage of 150 V and a current of 4.95 µA. Further, both the dual-mode TENG devices are demonstrated to explore self-powered applications by integration with robotics tilt table and biomechanical energy harvesting. © 2022 Elsevier LtdFALS

A new insight into the ZIF-67 based triboelectric nanogenerator for self-powered robot object recognition

Harvesting mechanical energy from the surroundings can be a promising power source for micro/nano-devices. The triboelectric nanogenerator (TENG) works on the principle of triboelectrification and electrostatic induction. So far, metals and polymers have mostly dominated the conventional triboelectric series, but there is a need to find novel materials to extend the triboelectric series and further improve the performance of a TENG. Herein, a zeolitic imidazole framework (ZIF-67) was synthesized using a room temperature solvent-assisted route. Extensive material analysis was performed to understand its structural and chemical properties. Further, a simple vertical contact mode S-shaped TENG device (abbreviated further as S-TENG) was fabricated using an additive manufacturing approach. ZIF-67 acted as a positive triboelectric layer while Teflon/PDMS acted as a negative triboelectric layer. The multi-unit S-TENG device was further utilized for self-powered recognition of the various gaits using a digital signal processing approach. The S-TENG device based on ZIF-67 and Teflon produced a voltage of 118 V, a current of 1.7 μA, and a power density of 15 μW cm2at a load resistance of 50 MΩ. The gait analysis of different volunteers was recorded by employing the S-TENG device and the digital signal processing route to effectively distinguish the gait patterns for the prevention of falls and injury. The S-TENG device was utilized to charge a commercial capacitor for powering a wristwatch and further it was attached to a robotic gripper for object identification. © The Royal Society of Chemistry 2021.1