Strategic energy-level modulation in porous heterojunctions: advancing gas sensing through Type-I to Type-II transitions

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.