A high surface area silica-supported aldehyde as a flow-compatible amine scavenger

Abstract

A silica-supported aldehyde scavenger (SSA-3) was prepared from SBA-15 silica by sequential NaOH activation, alkylation with 1,2-dichloroethane, and Kornblum oxidation of the resulting alkyl chloride in DMSO/K₂CO₃. The material was characterised by FTIR, PXRD, TGA/DSC, SEM, and BET physisorption, confirming successful surface functionalisation and a dramatic increase in surface area upon imine formation with probe amines. Loading capacity was experimentally determined to be 0.43–1.31 mmol g⁻¹, comparable to commercial polystyrene-aldehyde resins. A D-optimal design of experiments (22 runs) evaluated the effects of solvent type (mapped by PCA), flow rate (0.1–1.0 mL min⁻¹), temperature (30–90 °C), and amine concentration (0.2–1.0 M) on scavenging efficiency. Only solvent type had a significant influence on performance: hydrophobic solvents afforded near-quantitative scavenging, while polar non-polarisable solvents (notably acetonitrile) reduced efficiency to approximately 75% due to a solvation screening mechanism. The scavenger is flow-compatible and demonstrates utility as an in-line purification tool for continuous flow synthesis of small-molecule libraries.