known as/known for/known to do something

Here's how we should use these:

known to do something

Examples

• Smoking cigarettes is known to cause cancer. 
• Pandas are known to be an endangered species.
• Tomomi is known to come late to class sometimes.

Usually, we say known to do something in two different ways. First, when we want to talk about some fact that people have learned.

We also use this when we are talking about the habits of someone or something that other people know about.

known for

Examples

• The Pomo of California were known for their basket making.
• New York City is known for its tall buildings and busy lifestyle.
• Dolphins are known for their intelligence and playfulness.

We use known for when we want to talk about the reputation of something.

known as

Examples

• In some parts of the United States, the lynx is known as a puma.
• An irrational fear, one that has no basis in experience, is known as a phobia.
• Although she was born Su Chang, in the United States, she was known as Kathy.

We use known as when we want to talk about the name of somebody or something or its definition.