Retention of crystallinity of GUF-14 after exfoliation into MONs was demonstrated by the powder X-ray diffractogram collected on a sample isolated by centrifugation at 4500 rpm for 2 h (Figure ) Removal of monotopic "capping" carboxylate units at MOF/MON secondary building units can generate Lewis and Brønsted 53 acidic sites capable of promoting organic transformations. As the GUF-14 hxl and hns phases contain Zr6 clusters with potentially labile coordinated formate groups, we hypothesised that acid washing and subsequent activation could generate catalytically active acidic sites. Following the protocol reported by Stoddart and co-workers, samples of GUF-14 as the hxl and hns phases were washed with aqueous 1 M HCl (SI, Section S8.1). The materials obtained were collected by centrifugation and activated at 423 K, with 1 H NMR spectra of NaOD digests showing loss of >80% of capping formats and no structural degradation observed by PXRD. Their catalytic activities towards the imine condensation reaction between 4′-fluoroacetophenone and benzylamine in toluene were assessed and compared with those of pristine samples of the Zr-EDB MOF in the fcu topology (SI, Section S8.2). After 24 h, F NMR spectroscopy (Table )