Recovering DMF from a peptide coupling reaction containing HOBt and DCU is doable but requires some care due to the nature of the by-products. A few important considerations due to the presence of HOBt and DCU:

• Remove DCU by filtration: DCU is poorly soluble in DMF and typically precipitates out after the reaction. Cooling the reaction mixture (e.g., to 0–4 °C) can help with more complete precipitation before filtration.
• Dealing with HOBt: HOBt is soluble in DMF and not easily removed by filtration. Importantly, dry HOBt is potentially explosive, so avoid evaporating the solvent to complete dryness. If further purification is needed, distillation under reduced pressure can be used—only under controlled and safe lab conditions.
• Recovering DMF: After DCU removal, DMF can be recovered via rotary evaporation or short-path distillation under vacuum. However, some residual HOBt or other byproducts may co-distill, so the recovered DMF is best reserved for non-critical reactions unless it's further purified and dried.

In general, while DMF recovery is feasible at lab scale, reusing it in peptide synthesis—especially in coupling steps—is not always advisable if high purity is essential.

Hope this helps!