Merci de venir

Question

Why can’t merci de  venir be translated as thanks for coming?

Accepted Answer

Hi Margaret, 
As it says in the lesson -
"In French, you can use merci de + [infinitif] to express Please + [do something] in a formal/professional context."
It refers to an action which has not taken place yet :

Merci d'apporter un cadeau symbolique = Please bring a symbolic gift 
Merci d'arriver à l'heure = Please arrive on time

Bonne Continuation!

Answer

Merci de venir -- thank you for coming. In French, this is a very polite request for someone to come. If you want to make it clear that you are thanking someone, you can say merci d'être venu(e). Usually there is no confusion between the two, because if you're thanking someone for something he hasn't done yet, it can only be a polite request.

Answer

To thank someone for "having come" you need to use «merci d'être venu» as it is a completed action. (Merci d'avoir past participle for verbs that use avoir in passé composé). Using «merci de venir» (or any other verb infinitive) is effectively saying 'please come' (please verb). In English we might say "thanks in advance for coming" (or whatever the infinitive indicates)

https://www.frenchspanishonline.com/magazine/thank-you-for-merci-pour-or-merci-de/