Pandas can load data from Postgres directly:

import psycopg2
import pandas.io.sql as pdsql

conn = psycopg2.connect(...)

the_frame = pdsql.read_frame("SELECT * FROM %s;" % name_of_table, conn)

If you have a recent pandas (>=0.14), you should use read_sql_query/table (read_frame is deprecated) with an sqlalchemy engine:

import pandas as pd
import sqlalchemy
import psycopg2

engine = sqlalchemy.create_engine("postgresql+psycopg2://...")

the_frame = pd.read_sql_query("SELECT * FROM %s;" % name_of_table, engine)
the_frame = pd.read_sql_table(name_of_table, engine)

This answer might be helpful: How do I get list of all tables in a database using TSQL?

Trying changing your SQL string to:

sql = """
SELECT * FROM information_schema.tables
"""