Development of a 4,4′-biphenyl/phosphine-based COF for the heterogeneous Pd-catalysed telomerisation of 1,3-butadiene

Abstract

The improved synthesis, characterisation and application of a microporous 4,4′-biphenyl/phosphine-based covalent organic framework (COF) for the heterogeneous Pd-catalysed telomerisation of 1,3-butadiene with phenol and glycerol are presented. The solid polyphosphine is amorphous, microporous and an excellent support for Pd(acac)₂. Solid-state NMR and DRIFT analysis of materials of varying Pd-loading show that bis-phosphine complexes of palladium are preferably formed. Under solvent- and base-free conditions, high conversions and selectivities are obtained for this catalyst material with both phenol and glycerol as substrates. The product selectivity, with both butenylation and telomerisation activity observed with phenol, can be tuned by variation of the metal loading. For glycerol it is shown that the selectivity to the undesired tri telomer is low under all applied conditions and, remarkably, that the heterogeneous catalyst outperforms its homogeneous PPh₃-based counterpart.