Related Experiment Video
Updated: Sep 14, 2025

Infrared Degenerate Four-wave Mixing with Upconversion Detection for Quantitative Gas Sensing
Published on: March 22, 2019
Strategic energy-level modulation in porous heterojunctions: advancing gas sensing through Type-I to Type-II
Yong-Jun Chen1,2, Yi-Ming Xu1,3, Xiao-Liang Ye1,2
1State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences (CAS) Fuzhou, Fujian, 350002, PR China.
Abstract:
To significantly enhance reaction efficiency of porous heterojunctions in various applications, precise engineering of customization heterostructures through energy-level modulation is indispensable. Herein, the preparation of a core-shell porous heterojunction, UiO-66@TDCOF, is reported. Taking advantage of adjustable structure of metal-organic frameworks (MOFs), the energy-level of UiO-66 core is tailored to precisely align with that of porphyrin-based covalent organic framework (denoted as TDCOF) shell. As a results, the heterojunction transitions flexibly from a type-I to a type-II configuration, which remarkably enhances the efficiency of charge separation under light irradiation, resulting in exceptional performances in chemiresistive gas sensing. Notably, the sensitivity of (NH2)1.24-UiO-66@TDCOF towards NO2 is at a high level among all reported heterojunctions under visible-light condition, surpassing the majority of previously reported MOF and COF materials. This research not only presents a strategy for the design of heterojunctions but also gives an approach to material design tailored for chemical applications.
Related Concept Videos
Fermi Level Dynamics
Electron affinity in semiconductors refers to the energy gap between the minimum of its conduction band and the vacuum level and it is a critical parameter in determining how easily a semiconductor can accept additional electrons.
The work...
Types of Semiconductors
Fermi Level
At absolute zero temperature, electrons fill all energy states up to the Fermi level, leaving upper states empty. As the temperature rises,...
Biasing of Metal-Semiconductor Junctions
In Schottky junctions, where the semiconductor is n-type, applying a positive voltage to the metal relative to the semiconductor reduces its Fermi...
Metal-Semiconductor Junctions
Schottky Barriers
Schottky barriers arise when a metal with a work function (Φm) contacts a semiconductor with a different work function (Φs). Initially, electrons transfer until the Fermi levels of the metal and semiconductor align at equilibrium. For instance, if Φm > Φs, the semiconductor Fermi level is higher than the metal's before contact. The...
Energy Bands in Solids
Band Formation:
When atoms are brought close together, as in a solid, these discrete energy levels begin to split due to the overlap of electron orbitals from adjacent atoms. This split occurs because of the Pauli exclusion principle, which states...

