To conduct the synthesis, the functionalized glass wool 1 was prepared (Scheme 2). The required compounds 2 and 3 were purchased from commercial sources. Compound 4 was synthesized on-stie (see supporting information and Scheme s1). Glass wool (Figure ) as depicted (a) The length of glass wool can be more than 1 cm. Its effect on loading is minimal. (b) Density is that of solid glass. (c)To achieve close to resistance-free flow of liquid, the diameter of glass beads needs to be ~50 µm or larger. (d) The effect of the length of glass wool on loading is minimal and is omitted in the formula. The units for d and r in the formulas are g/mL and µm, respectively. Details for deriving the formulas are in the supporting information. (e) Calculated value assuming 3.2 molecules per nm 2 . (f) Given by the manufacturer of the CPG tested. (g) Values from the literature. (h) 25 µmol/g is used for the calculation. (i) 2.5 mmol/g is used for the calculation. (j) Measure using trityl assay using literature procedure. (k) Oligo obtained per gram of solid support after CBP purification as determined with Qubit 4 Fluorometer.