Electron-Beam-Driven Ag Nanoparticle Evolution at ZIF-8/Ag3PO4 Heterointerfaces

Abstract

Silver orthophosphate (Ag3PO4) is a promising visible-light photocatalyst in which lattice Ag+ ions can be reduced to metallic Ag0 under external stimuli, but the subsequent evolution of these Ag species at heterogeneous interfaces remains poorly understood. Coupling Ag3PO4 with porous, electron-transport-active frameworks such as zeolitic imidazolate framework-8 (ZIF-8) offers a route to modulate this behavior, yet how reduced Ag species migrate across such heterointerfaces remains unexplored. Here, electron-beam irradiation (EBI) combined with time-resolved high-resolution transmission electron microscopy (HRTEM) reveals a previously unreported sequence of structural transformations in ZIF-8/Ag3PO4 heterostructures. Under continuous irradiation, reduced Ag species generated within Ag3PO4 diffuse through the ZIF-8 framework toward its outer surface, where they nucleate and grow into metallic Ag nanoparticles; prolonged exposure then drives their redistribution into the Ag3PO4 matrix, showing that this interfacial silver transport is fully dynamic. Density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations reproduce the early stages of this process, revealing preferential electron accumulation within Ag3PO4, enhanced mobility of reduced Ag species, and the formation of Ag–Ag dimers as nucleation precursors. Together, these experimental and theoretical results establish a mechanism for electron-induced interfacial mass transport in MOF/semiconductor heterostructures, in which ZIF-8 acts not as a passive support but as an active medium that mediates silver migration and reversible interfacial reconstruction.