The situation in English is a little bit complicated, because the adverb is completely different from the preposition.
The car is in front of the door.
(actually it is a pronominal adverb)
He stays before.
Furthermore English distinguish between mouvement and static position.
static position: He stays at the front.
mouvement: He goes ahead.
To all these different English adverbs and prepositions correspond something with frente.
In Portuguese we get the adverb that corresponds to the preposition by leaving out the de.
em frente de or em frente a (preposition in front of / at the other side), em frente (in front of / at the other side) both cannot be used in a metaphorical sense
O museu fica em frente do jardim.
=> The museum is located in front of the garden.
Um edifício alto está sendo construído em frente.
=> At the other side they are constructing a high building.
à frente de (ahead), à frente (before) as well in metaphorical sense
Ele era à frente de seu tempo.
=> He was ahead of his time.
O acidente foi provocado por causa de outro veículo que estava à frente e freou bruscamente.
=> The accident was caused by a car before that suddenly braked.
para a frente de (in front of), para frente (forward) as well in metaphorical sense
Ele saltou para a frente de um comboio.
=> He jumped in front of a train.
A União Europeia tem de olhar para a frente.
=> The European Union has to look forward.
Diante as an adverb doesn't exist alone, it is always combined with a preposition (em diante, por diante, a diante), wherin obviously the adverb alone can't establish any relationship to a following complement.
preposition diante de (before, in front of)
Temos muito tempo diante de nós.
We have a lot of time before us.
Eu estou aqui, diante de você.
I am here, in front of you.
A versão que tenho diante de mim é a francesa.
The version I have in front of me is in French. .
adverbs only with prepositions
Temos por diante uma importante tarefa.
We have an importante duty in front of us.
Temos de olhar para diante e não para trás.
We have to look forward and not backwards.
A luz avança para diante.
Light moves forward.
Choose the right option in the following sentences.