*3.4. Catalytic Cyanosilylation*

Typical reaction mixtures were prepared as follows: in a small vessel, solid catalyst (typically 3 mol%) was suspended in dichloromethane (2.5 mL) and then an aldehyde substrate (0.50 mmol) and a cyanosilylation agen<sup>t</sup> trimethylsilyl cyanide (1.0 mmol) were added. The reaction was kept under stirring at room temperature (~25 ◦C) for the desired time. Then, the catalyst was separated by centrifugation and the filtrate was subjected to solvent evaporation under reduced pressure to form a crude solid. This solid was dissolved in CDCl3 and analyzed by 1H NMR spectroscopy for product quantification (for details, see Supplementary Materials, Figures S5 and S6). In the catalyst recycling experiments, the catalyst was centrifuged, washed with CH2Cl2, dried at room temperature, and reused in subsequent steps that were done as described above. Blank tests without any catalyst or using metal salt or H4dpa as catalyst were also carried out for comparative purposes.


**Table 3.** Crystal data for CPs **1**−**3**.
