Following crystal structure characterisation, scanning electron microscopy (SEM) images confirmed the expected differences in microstructure. A-CuHHTP was formed of weakly agglomerated 'flake-like' particles, with diameters of 0.5 -2.9 μm and thicknesses of 30 -110 nm based on measurements on a range of different particles seen in SEM images (Fig. ; SI Fig. , Table ). This gives a lengthto-width aspect ratio for this sample of 0.01 -0.23. Transmission electron microscopy (TEM) confirmed that the pores run perpendicular to the face of the flakes, showing that particles of A-CuHHTP have a pore network made up of many short pores (Fig. , SI Fig. ). This illustrates that using ammonia as a modulator in the synthesis of Cu3(HHTP)2 leads to inhibited crystal growth in the c crystallographic direction and enhanced growth in the ab plane. In marked contrast, samples of B-CuHHTP showed weakly agglomerated 'rod-like' particles, with diameters of 110 -340 nm and lengths of 0.5 -4 μm observed in SEM images (Fig. ; SI Fig. , Table ). TEM images, and the determination of the fringe spacing in these, confirmed that the pores run parallel to the length of the rods (Fig. ). This verifies that employing DMF as a modulator leads to a significant increase in growth in the c crystallographic direction, with a length-to-width aspect ratio of 1 -37 estimated from SEM images. This results in a pore network of relatively long pores and few pore openings, contrasting with that of A-CuHHTP. Interestingly, comparing the fast Fourier transform (FFT) image from this sample with simulated FFT images from Cu3(HHTP)2 with both eclipsed and near-eclipsed stacking sequences supports the XRD analysis that B-CuHHTP has near-eclipsed layer stacking (SI Fig. ). While both A-CuHHTP and B-CuHHTP displayed weak agglomeration, C-CuHHTP exhibited a strongly agglomerated microstructure of ca. 0.5 -1 μm spherical clusters of nanoscale 'flake-like' particles (Fig. ). Due to the thickness of the agglomerates, TEM imaging was unable to examine the pore network in this sample. These results confirms that coordination modulation is an effective means to reliably obtain layered MOFs with distinctly different sample microstructures. It must be noted, however, that all samples displayed relatively large polydispersities, with a range of length-to-aspect ratios observed for the crystallites in each sample. Future work should focus on developing new synthesis methods to produce samples with more uniform particle dimensions.