Visible-Light-Activated Type II Heterojunction in Cu₃(hexahydroxytriphenylene)₂/Fe₂O₃ Hybrids for Reversible NO₂ Sensing: Critical Role of π–π* Transition

Abstract

Metal–organic frameworks (MOFs) with high surface area, tunable porosity, and diverse structures are promising platforms for chemiresistors; however, they often exhibit low sensitivity, poor selectivity, and irreversibility in gas sensing, hindering their practical applications. Herein, we report that hybrids of Cu 3 (HHTP) 2 (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) nanoflakes and Fe 2 O 3 nanoparticles exhibit highly sensitive, selective, and reversible detection of NO 2 at 20 °C. The key parameters to determine their response, selectivity, and recovery are discussed in terms of the size of the Cu 3 (HHTP) 2 nanoflakes, the interaction between the MOFs and NO 2 , and an increase in the concentration and lifetime of holes facilitated by visible-light photoactivation and charge-separating energy band alignment of the hybrids. These photoactivated MOF–oxide hybrids suggest a new strategy for designing high-performance MOF-based gas sensors.

Type-II BiVO4/Ni3(hexahydroxytriphenylene)2 heterojunction photoanodes for effective photoelectrochemical reaction

“…Co 3 (HHTP) 2 and Cu 3 (HHTP) 2 are two other potential conductive MOFs 28 that were coated onto BiVO 4 by a solvothermal reaction to investigate their photoelectrochemical performance. Upon their use, the photocurrent density increased to 2.25 and 1.77 mA cm −2 (Fig.…”

Surface Modification of 2D Photocatalysts for Solar Energy Conversion

“…[ 103–106 ] However, another group of metal oxides (e.g., TiO 2 , ZnO, Fe 2 O 3 , and Cu 2 O) with intrinsic ordered molecular structures in 3D cannot be exfoliated into a layered structure directly. [ 107–110 ] Therefore, it is of great significance to develop bottom‐up self‐assembly strategies for reducing the thickness of the materials with intrinsic ordered 3D structures. Sun et al.…”

Metal-Organic-Frameworks: Low Temperature Gas Sensing and Air Quality Monitoring

“…The former could be attributed to its high resistance change (orders of magnitude) upon NO 2 exposure and the significantly large crystallite size of Ni-MOF-74 (up to 100's of µm), making the difference in mass transport of NO 2 less dominant at short time intervals. The issue of prolonged recovery time towards NO 2 gas sensing might be addressed by using a photoactivation approach [88].…”